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Patient knowledge of and adherence to oral anticoagulation therapy after mechanical heart-valve replacement for congenital or acquired valve defects
Patient knowledge of and adherence to oral anticoagulation therapy after mechanical heart-valve replacement for congenital or acquired valve defects Sara Van Damme, MSc, RNa, Kristien Van Deyk, MSc, RNa, Werner Budts, MD, PhDa, Peter Verhamme, MD, PhDb, Philip Moons, PhD, RNa,c,* a
Division of Congenital and Structural Cardiology, University Hospitals of Leuven, Leuven, Belgium, University Hospitals of Leuven, Leuven, Belgium b Department of Vascular Medicine and Hemostasis, University Hospitals of Leuven, Leuven, Belgium c Center for Health Services and Nursing Research, Katholieke Universiteit Leuven, Leuven, Belgium
article info
abstract
Article history: Received 25 September 2009 Revised 2 November 2009 Accepted 19 November 2009 Online 4 June 2010
Objective: This study sought to determine (1) the level of knowledge that mechanical heart-valve patients (because of congenital heart disease or acquired heart-valve defects) have about oral anticoagulation therapy; and (2) to what extent these patients adhere to this therapy.
Keywords: Knowledge Adherence Anticoagulation Heart defects Congenital Heart valve Nursing
Methods: This descriptive, cross-sectional study included 57 patients. Knowledge was measured using the Knowledge of Oral Anticoagulation Tool. Adherence was assessed with a visual analogue scale and the Swiss HIV Cohort Study Adherence Questionnaire. Results: Patients poorly understood symptoms relevant to over-anticoagulation and the effects of alcohol and vitamins on oral anticoagulants. The knowledge level of patients with congenital heart disease and acquired heart-valve defects did not differ significantly. Three-quarters of patients claimed to be 100% adherent to oral anticoagulant therapy. Conclusion: Most patients lack knowledge about oral anticoagulants, and one fourth of patients do not fully adhere to therapy. Cite this article: Van Damme, S., Van Deyk, K., Budts, W., Verhamme, P., & Moons, P. (2011, MARCH/ APRIL). Patient knowledge of and adherence to oral anticoagulation therapy after mechanical heart-valve replacement for congenital or acquired valve defects. Heart & Lung, 40(2), 139-146. doi:10.1016/ j.hrtlng.2009.11.005.
Lifelong treatment with oral anticoagulants is necessary in patients with 1 or more mechanical heart valves, to prevent cardioembolisms and preserve
adequate functioning of the mechanical heart valve.1 The use of oral anticoagulants is very complex, because of their narrow therapeutic range.2 Incorrect
* Corresponding author: Philip Moons, PhD, RN, Center for Health Services and Nursing Research, Katholieke Universiteit Leuven, Kapucijnenvoer 35, Postbox 7001, B-3000 Leuven, Belgium. E-mail address: [email protected] (P. Moons). 0147-9563/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.hrtlng.2009.11.005
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use can lead to life-threatening bleeding, on the one hand, or catastrophic thromboembolisms, on the other. Previous studies showed that patient compliance is crucial in adequate anticoagulation therapy.3,4 The cohort study of Waterman et al showed that 23% of all international normalized ratio (INR) values for the anticoagulant warfarin were outside the target range.4 Thirty-six percent of these values could be explained by changes in the patient’s eating behavior, misunderstanding of the drug dose, skipping a dose, missing consultations in an outpatient clinic, excessive consumption of alcohol, or failure to obtain timely and correct prescriptions.4 These findings suggest that successful therapy depends on a patient’s understanding of the treatment. However, patients’ knowledge of oral anticoagulation therapy is lacking. Some studies found that more than half of patients on anticoagulants had poor knowledge of the therapy.5-10 One study reported that 63% of patients did not know the correct dose of their medication.7 Another study found that 60% of patients could not list the potential side effects of overdosing or underdosing, and that 28% of patients did not know why they had to take anticoagulants.8 In other studies, 43% to 46% of patients did not know why they had to take anticoagulants.9,10 Some investigations explored the possible relationship between knowledge of, and adherence to, anticoagulation therapy. One study found a positive correlation between patients’ knowledge of oral anticoagulation therapy and the total number of INRs within the target range.11 Other studies, however, failed to find such a relationship.5,12 Moreover, most investigations did not focus on patients with a mechanical heart valve, but recruited a range of patients on anticoagulants. To date, no study has reported on mechanical heart-valve patients who received their valves because of a congenital heartvalve defect. Therefore, the present study sought to (1) assess the level of knowledge that mechanical heart-valve patients possess about oral anticoagulation therapy (only patients with congenital heart disease [CHD] or acquired heart-valve defects [AHDs] were studied); (2) determine to what extent these patients adhered to oral anticoagulation therapy; and (3) compare the knowledge and adherence of CHD and AHD patients.
Methods Study Population We used a descriptive, cross-sectional design. Patients were included if they were aged 18 years or older, if they were Dutch-speaking and literate, and if they had a mechanical heart valve because of CHD or an AHD.
Congenital heart disease patients were recruited from the computerized database of a Pediatric and Adult Congenital Heart Disease Program at an institution in Belgium. Patients with acquired heart-valve defects were eligible if they were undergoing regular follow-up for INR control at the University Hospitals Leuven, or if they were managed by a general practitioner and their blood samples for INR control were analyzed at the aforementioned university hospitals. Patients were excluded if they manifested mental retardation. Sixty-one patients met the inclusion criteria: 28 had CHD, and 33 had AHDs. Three patients refused participation, and 1 completed form was lost in the mail. Hence, 57 patients (93%) participated: 25 with CHD, and 32 with AHDs.
Variables and Measurements Demographic and Clinical Variables Demographic variables included gender and age. Clinical variables included primary diagnosis, type of mechanical heart valve, kind of oral anticoagulating drug, duration of therapy, type of follow-up, and frequency of INR control measurements. These variables were collected from patients’ medical records.
Knowledge We conducted a comprehensive literature search for an appropriate instrument to evaluate patients’ knowledge of oral anticoagulants. Eight questionnaires were identified.5,6,9-11,13-16 These questionnaires differed in layout, number of items, and aspects of knowledge. Only 3 of 8 instruments were evaluated for validity and reliability.13-15 However, none of these questionnaires was appropriate for the present study, because of length or difficulties with translation. Therefore, we developed a new questionnaire for patients with either CHD or AHDs. Five different knowledge domains dealt with oral anticoagulant treatments: (1) general information about the functioning of the medication, (2) possible side effects, (3) interactions with ingested food, (4) interactions with other medications, and (5) lifestyle.5,9-11,13,14,16 We developed a questionnaire comprising 10 multiple-choice questions, including 2 questions for each of the 5 knowledge domains. For each question, 4 possible answers were given, 1 of which was correct. To avoid wild guesses, we included as a possible answer, “I don’t know.”5 Thus, in the datacoding process, the patient’s answers could be evaluated as “right,” “wrong,” or “I don’t know.” A panel of 5 experts in oral anticoagulation medication evaluated the content validity of the newly developed questionnaire. They assessed the knowledge questionnaire according to form, content, and legibility. To evaluate the legibility and intelligibility of the questions (face validity), we performed a small pilot study with 3 patients who recently started oral anticoagulant therapy. On the basis of comments from experts and patients, we adjusted the knowledge
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questionnaire. The final questionnaire was called the Knowledge of Oral Anticoagulation Tool (KOAT). The full version of the instrument can be requested from the authors.
Results
Adherence
Demographic and clinical variables are shown in Table 1. The sample comprised 57 respondents: 35 were male, and 22 were female. The median age was 60 years. The aortic valve was the most frequently replaced heart valve in this study population. Fenprocoumon was the most commonly taken oral anticoagulant. The median duration of anticoagulation therapy was 10 years. The most prevalent heart defects in patients with CHD were congenital aortic stenosis (n ¼ 6; 24%), coarctation of the aorta (n ¼ 5; 20%), an Ebstein anomaly (n ¼ 3; 12%), and ventricular septal defects (n ¼ 3; 12%). Patients with AHDs were significantly older than patients with CHD (Table 1).
To evaluate patients’ adherence to anticoagulation treatment, we used 2 self-report questionnaires: the visual analogue scale (VAS) and the Swiss HIV Cohort Study Adherence Questionnaire (SHCS-AQ). The VAS scale is a horizontal line, ranging from 0% to 100%, on which respondents can indicate the percentage of prescribed doses they have actually taken over the last month. Hence, the VAS measures dosing adherence. The SHCS-AQ questionnaire measures drug-taking adherence and drug holidays. This questionnaire comprises 2 questions: “How often did you miss 1 dose of the medication in the last month?” and “Did you have a period of no drug intake for more than 24 hours in the last 4 weeks?” Previous studies suggest that both the VAS and SHCS-AQ demonstrate good psychometric properties.17,18 However, these questionnaires were not evaluated for use in patients on oral anticoagulation therapy.
Procedure The set of questionnaires was sent to all patients who met the inclusion criteria. An accompanying letter explained the goal and procedure of the study. Completing the questionnaires took about 15 minutes. The completed questionnaires could be returned in a preaddressed, prestamped envelope. If questionnaires were not returned within 2 months, the patient received a follow-up telephone call. Informed consent was assumed if the patient completed the questionnaires. After completing the study, every participant received the correct answers by mail as a feedback instruction. The study was approved by the Institutional Review Board of the aforementioned institution in Belgium.
Statistical Analysis Descriptive statistics for nominal and ordinal variables were expressed in percentages. Medians, quartiles, and ranges were calculated for continuous, non-normally distributed data. To test differences between the CHD and AHD groups, the c2 test and Fisher’s exact test were used for nominal-level data, and the MannWhitney U test was used for ordinal-level or continuous-level data. A possible relationship between knowledge and adherence was explored using binary logistic regression. The level of significance was set at P < .05. Data were analyzed using the Statistical Package of the Social Sciences, version 12.0 (SPSS, Inc., Chicago, IL).
Sample Characteristics
Knowledge The median total score on the knowledge questionnaire was 7 on a scale of 0 to 10. Nine patients (15.7%) answered more than 8 questions correctly, 45 patients (78.9%) answered between 5 and 8 questions correctly, and 3 patients (5.2%) answered fewer than 5 questions correctly. The median total score of CHD and AHD patients was 7. Almost all patients (94.7% and 98.2% of CHD and AHD patients, respectively) provided correct answers for questions regarding the name of the blood-clotting test and the effect of their oral anticoagulation medication (Table 2). More than 80% of respondents (87.7% and 80.7% of CHD and AHD patients, respectively) knew that their medication should be stopped a few days before certain surgical interventions, and that forgetting a dose of the medication increased the risk for thromboembolism. Furthermore, 75.4% of patients correctly listed paracetamol as a medicine that can be taken for headaches; 70.2% designated contact sports (such as horseback riding, judo, and football) as sports to avoid during the use of oral anticoagulation medication; and 61.4% knew what to do when a dose of the medication was missed. Less than half (43.9%) of the study sample knew that black-colored stools are an indicator that something is wrong with the concentration of medication in the blood; 43.9% knew that more than 2 consumptions of alcohol can thin the blood; and 21.1% knew that certain vitamins (eg, vitamin K) can influence their medication. When stratifying subjects according to CHD and AHD, more CHD patients knew the correct answers on questions about the influence of alcohol (56% vs 34.4% of CHD and AHD patients, respectively) and vitamin preparations (28% vs 15.6% of CHD and AHD patients, respectively). On the other hand, more AHD patients correctly answered the question regarding what medication was allowed for headaches (81.3% vs 68% of AHD and CHD patients, respectively), and the question
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Table 1 e Demographic and clinical variables of 57 patients with a mechanical heart valve Variables Age (y) Median (Q1; Q3) Range Gender, n (%) Female Male Duration of therapy with oral anticoagulants (y) Median (Q1; Q3) Range Heart valve replaced by a mechanical valve, n (%) Aortic Mitral Tricuspid Aortic and mitral Aortic, mitral, and tricuspid Type of follow-up, n (%) General practitioner Hospital Self-management Family member Type of oral anticoagulant, n (%) Fenprocoumon Acenocoumarol Frequency of follow-up, n (%) 2 weeks Every 3 weeks Every 4 weeks 5 weeks
All patients (n ¼ 57)
Congenital heart disease (n ¼ 25)
Acquired valve defects (n ¼ 32)
60 (Q1 ¼ 44; Q3 ¼ 69) 18-82
43 (Q1 ¼ 27; Q3 ¼ 50) 18-60
66.5 (Q1 ¼ 62; Q3 ¼ 74.7) 54-82
22 (38.6) 35 (61.4)
9 (36) 16 (64)
13 (40.6) 19 (59.4)
Test value P values U ¼ 10.500 P < .001 c2 ¼ .127 P ¼ .722 U ¼ 282.500
10 (Q1 ¼ 6; Q3 ¼ 22) .6-32
8 (Q1 ¼ 5; Q3 ¼ 19.125) 2-32
17 (Q1 ¼ 27; Q3 ¼ 24.75) .6-32
P ¼ .092 FE ¼ 7.993
35 (61.3) 13 (22.8) 3 (5.3) 5 (8.8) 1 (1.8)
16 (64) 6 (24) 3 (12) 0 (0) 0 (0)
19 (59.4) 7 (21.9) 0 (0) 5 (15.6) 1 (3.1)
34 (59.6) 19 (33.3) 3 (5.3) 1 (1.8)
21 (84) 0 (0) 3 (12) 1 (4)
13 (40.6) 19 (59.6) 0 (0) 0 (0)
56 (98.2) 1 (1.8)
24 (96) 1 (4)
33 (100) 0 (0)
6 (10.5) 12 (21.1) 35 (61.4) 4 (7)
3 (12) 6 (24) 14 (56) 2 (8)
3 (9.4) 6 (18.8) 21 (65.4) 2 (6.3)
P ¼ .053
FE ¼ 27.536 P < .001
FE* P ¼ .439 FE ¼ .822 P ¼ .913
Q1, first quartile; Q3, third quartile; INR, international normalized ratio; FE, Fisher’s exact test; U, Man-Whitney U test. * Fisher’s exact test value was not provided.
regarding the issue of the need to stop their medication a few days before a surgical intervention (93.8% vs 80% of AHD and CHD patients, respectively). However, statistical significance between groups was not achieved (Table 2).
Adherence On the VAS, 72.2% of patients indicated that they were 100% adherent. On the SHCS-AQ, 75% stated that they had not missed 1 dose of their medication during the last month. Of the remaining patients, 14.3% missed 1 dose during the last month, 7.1% missed 1 dose in the preceding 14 days, and 3.6% missed 1 dose during the last week. No patients reported a drug holiday, which was defined as missing 2 consecutive doses
Relationship Between Knowledge and Adherence No statistically significant association between any knowledge item and the VAS on adherence was found.
Discussion Patients’ knowledge of, and adherence to, oral anticoagulation medication therapy play a pivotal role in the prevention of life-threatening complications. The risk for bleeding or thromboembolisms increases with incorrect use.5,19 Despite these facts, previous studies demonstrated that knowledge and adherence in this patient population are often insufficient.3-10 Previous studies assessed only patients with acquired valve defects. Using a newly developed questionnaire, we investigated knowledge of and adherence to oral anticoagulation medication in congenital or acquired valve-disease patients who had one or more mechanical heart valves. Patients possessed much knowledge (ie, >80% of patients provided the correct answer) about the name of the blood-clotting test, the effect of their oral anticoagulation medication, the increased risk for developing thromboembolisms when a dose of the medication was missed, and the need to stop their medication a few days before certain surgical interventions. Patients
Table 2 e Distribution of answers to knowledge of oral anticoagulation tool n (%)
All patients (n ¼ 57) Right
I don’t know
Right
Wrong
Acquired valve defects (n ¼ 32)
I don’t know
Right
Wrong
I don’t know
Test value and P value
54 (94.7)
0 (0)
3 (5.3)
23 (92)
0 (0)
2 (8.0)
31 (96.9)
0 (0)
1 (3.1)
c2 ¼ .669 P ¼ .413
56 (98.2)
0 (0)
1 (1.8)
24 (96)
0 (0)
1 (4.0)
32 (100)
0 (0)
0 (0)
25 (43.9)
6 (10.5)
26 (45.6)
12 (48)
4 (16.0)
9 (36.0)
13 (40.6)
2 (6.2)
17 (53.1)
c2 ¼ 1.303 P ¼ .254 c2 ¼ .310 P ¼ .578
46 (80.7)
7 (12.3)
4 (7.0)
21 (84)
3 (12.0)
1 (4.0)
25 (78.1)
4 (12.5)
3 (9.4)
25 (43.9)
21 (36.8)
11 (19.3)
14 (56)
6 (24.0)
5 (20.0)
11 (34.4)
15 (46.9)
6 (18.8)
12 (21.1)
13 (22.8)
32 (56.1)
7 (28)
6 (24.0)
12 (48.0)
5 (15.6)
7 (21.9)
20 (62.5)
43 (75.4)
13 (22.8)
1 (1.8)
17 (68)
8 (32.0)
0 (0)
26 (81.3)
5 (15.6)
1 (3.1)
40 (70.2)
1 (1.8)
16 (28.1)
18 (72)
0 (0)
7 (28.0)
22 (68.8)
1 (3.1)
9 (28.1)
50 (87.7)
2 (3.5)
5 (8.8)
20 (80)
1 (4.0)
4 (16.0)
30 (93.8)
1 (3.1)
1 (3.1)
35 (61.4)
16 (28.1)
6 (10.5)
15 (60)
8 (32.0)
2 (8.0)
20 (62.5)
8 (25.0)
4 (12.5)
c2 ¼ .311 P ¼ .577 c2 ¼ 2.666 P ¼ .103 c2 ¼ 1.293 P ¼ .255 c2 ¼ 1.330 P ¼ .249 c2 ¼ .071 P ¼ .790 c2 ¼ 2.463 P ¼ .117 c2 ¼ .037 P ¼ .847
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1. What kind of blood test can be performed to evaluate the effectiveness of oral anticoagulating medication? 2. What is the effect of oral anticoagulating medication? 3. What complaint could indicate that there is something wrong with the amount of medication in the blood? 4. What are the consequences when a person forgets a dose of the medication? 5. Drinking more than 2 drinks of alcohol during a party, may cause ____. 6. Which of the following products can possibly have an effect on the amount of medication in the blood? 7. What kind of medication are you allowed to take in case of headache? 8. Which of the following sports should be avoided? 9. What should you do with the oral anticoagulating medication in case of surgery? 10. What do you do when you forget a dose of the medication and you notice it the next day?
Wrong
Congenital heart disease (n ¼ 25)
143
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displayed moderate knowledge (50% to 80% correct answers) about what kind of medication can be taken for headaches, what kind of sports should be avoided, and what to do when a dose of the medication was missed. Patients exhibited poor knowledge (<50% correct answers) about symptoms that indicate a problem with the level of medication in their blood, the blood-thinning effect of alcohol, and the influence of certain vitamins on their medication. Although not statistically significant, differences in the level of knowledge between CHD and AHD patients were evident for some questions. Comparing the results of our study with those of previous investigations revealed similarities. We corroborated the finding that patients have much knowledge about the effects of anticoagulants,9 but moderate to poor knowledge about interactions between food or vitamin products and oral anticoagulation medications.6,10,11 On the other hand, more patients in our study (61.4%) correctly answered the question of what to do when a dose of the medication was missed, than did patients (35%) in the study of Tang et al.11 In general, overall knowledge scores in previous studies were lower than those in our investigation.5,11 We found that three quarters of the patients were 100% adherent to their medication therapy. No difference was evident for median total scores between CHD and AHD patients. No statistically significant relationship was found between knowledge and adherence. The level of adherence was substantially better in our study than in that of Davis et al,5 who found only 50% of patients to be fully adherent. In another study, knowledge of oral anticoagulation level and INR values positively correlated with the target range.11 The results of different studies, however, cannot be compared, because different methods were used to measure adherence. Our results demonstrate that structured educational interventions should be used to improve the level of knowledge in patients on oral anticoagulation medications. In addition, adherence-improving strategies should be implemented to target the one quarter of patients who reported nonadherence. Nurses can play a pivotal role in the implementation of educational and adherence-promoting interventions. Indeed, the growing number of advanced-practice nurses for congenital heart disease20,21 or specialized anticoagulation services22 results in a workforce that is trained and dedicated to take on this role. Only 3 of 57 participating patients were under selfmanagement. At the time of our study (2007 and 2008), the reimbursement system in Belgium did not reimburse patients for buying point-of-care equipment for checking INRs. On the other hand, blood checks by general practitioners or hospitals were to a large extent reimbursed by the compulsory health-insurance system. Such a system discourages patients to check their INR themselves. New regulations are in progress in Belgium. Hence, the number of patients under
self-control and self-management will increase in the future.
Clinimetric Aspects of the KOAT Before an instrument can be used in research or clinical practice, aspects of its validity, reliability, and responsiveness should be evaluated. The traditional views focusing on content, criterion-related, and construct validity are no longer appropriate,23 and pose significant challenges to instruments that assess levels of knowledge in individuals. Therefore, the standards for educational and psychological testing, as developed by the American Educational Research Association; American Psychological Association, National Council on Measurement in Education, and Joint Committee on Standards for Educational and Psychological Testing, are more applicable in evaluating the clinimetric properties of the KOAT.24 Standards for educational and psychological testing consider validity as a unitary concept, for which evidence along 5 lines has to be accumulated: evidence based on test content, internal structure, relationship with other variables, response processes, and consequences of testing.24 Evidence based on test content refers to the themes, wording, and format of the questions of an instrument, as well as the guidelines for procedures regarding administration and scoring.24 With respect to KOAT, we evaluated test content by forming a panel of 5 experts in oral anticoagulation medication to assess the form, content, and legibility of KOAT. Furthermore, 3 patients were asked to appraise the legibility and intelligibility of the questions. On the basis of comments from experts and patients, we adjusted the questionnaire. Additional evidence regarding test content was derived from completed questionnaires. We found that no data were missing in the KOAT. This finding suggests sufficient comprehension of the items, attainable data within the context of care, and construct relevance.25 Analysis of the internal structure of a test indicates the degree to which the relationship among items and components conforms to the construct as operationally defined.24 Evidence on internal structure can be provided by factor analysis. For instance, it could be useful to investigate whether the 5 different knowledge domains (ie, functioning of the medication, possible side effects, interactions with ingested food, interactions with other medication, and lifestyle) are identifiable in 5 factors. Factor analysis, however, was not feasible for the data in the present study because of the limited sample size and non-normal distribution of data. Evidence for the relationship with other variables corresponded with the association between test scores and other variables that the test was expected to correlate with or predict.24 In this respect, the scores on the instrument under study are compared with those of a gold standard. With respect to the assessment of level of knowledge, there is no gold standard.
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In addition, existing questionnaires were not appropriate for use in the present study. This was precisely the rationale for developing the KOAT. Thus, we could not use another knowledge instrument in our study to compare with KOAT scores. Evidence based on response processes refers to the question, “To what extent does the type of performances or responses in which examinees engage fit the intended construct?”25 This can be investigated by undertaking interviews or focus groups with respondents to determine the reasons for providing certain answers to questions. In other words, a sequential quan-qual design is needed to provide evidence on response processes.26 Including evidence on the consequences of testing is a relatively new concept. It pertains to the benefits or negative consequences of a test. For this purpose, both researchers and respondents can be interviewed. The objective of our project was to improve the educational care of our patients. Hence, no specific negative consequences of the test were anticipated. On the contrary, we provided feedback to respondents, to educate them about different aspects of anticoagulation therapy. Evidence based on reliability refers to the internal consistency, interrater reliability, and stability of an instrument. The reliability of internal consistency may be assessed by calculating Cronbach’s a for the items of KOAT. However, the calculation of Cronbach’s a is only useful if the items on a scale are conceptually related to each other.27 The items in KOAT are deliberately and appropriately not homogeneous. For instance, knowing the function of anticoagulation is not necessarily related to a knowledge of interactions with ingested food. Therefore, the calculation of an a-coefficient for KOAT is not useful.27 Moreover, the assessment of interrater reliability of KOAT is irrelevant, because it is a self-report instrument. Testing the stability of this instrument is possible. However, a traditional test-retest approach cannot be used. Knowledge can change over time, and is therefore not a stable construct. Hence, the application of a strategy is imperative in which the stability of a construct (knowledge) and the stability of a tool (KOAT) can be distinguished. Such a method was described by Knapp et al, but requires at least 3, and preferably 4, consecutive measurements.28 Because 4 measurements were not possible within the time frame of the project, we refrained from testing the stability of the KOAT. Evidence based on responsiveness refers to the ability of an instrument to detect clinically important changes.29 Responsiveness can be explored by examining changes in scores before and after the implementation of an educational program. We are considering such a project in the future. In addition, responsiveness can be tested by identifying floor and ceiling effects of the instrument. As indicated in Table 2, responses on the items of KOAT were welldistributed, suggesting that this instrument does not exhibit floor or ceiling effects.
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Methodological Limitations The results of the present study should be interpreted with caution because of some methodological limitations. First, although we had an attrition rate of only 7%, the sample in our study was rather small. Therefore, our results cannot be generalized to the entire population of patients with mechanical heart valves and anticoagulating drugs. Second, we had to devise a new instrument to measure knowledge, because existing questionnaires were not applicable. The first evidence of the validity and responsiveness of KOAT was established. However, other clinimetric aspects of KOAT should be scrutinized in future research. To measure adherence, we used a VAS and the SHCS-AQ. The SHCS-AQ was initially developed for HIV patients. Although we cannot transfer the questionnaire to other patient populations as such, adherence to medication in patients with mechanical heart valves is as critically important as in HIV patients. Therefore, we assumed that this questionnaire would be appropriate for our purpose. Future studies should validate these measurements in anticoagulation therapy.
Conclusions We investigated patient knowledge of, and adherence to, anticoagulation therapy in patients with 1 or more mechanical heart valves implanted because of a CHD or a noncongenital heart disease. A new questionnaire, called KOAT, was developed for this study. Moderate to poor knowledge was evident for the kinds of medication that can be taken in case of headaches, the sports to be avoided, what to do when a dose of medication is forgotten, symptoms that can indicate a problem with the level of medication in the blood, the blood-thinning effect of alcohol, and the influence of certain vitamins on medications. One quarter of the patients admitted to less than full adherence. These findings indicate that room exists for structured educational interventions and adherence-promoting strategies.
References 1. Koertke H, Zitterman A, Tenderich G, Wagner O, ElArousy M, Krian A, et al. Low-dose oral anticoagulation in patients with mechanical heart valve prostheses: final report from the early selfmanagement anticoagulation trial III. Eur Heart J 2007; 28:2479-84. 2. Ufer M. Comparative pharmacokinetics of vitamin K antagonists. Clin Pharmacokinet 2005;44:1227-46. 3. Kimmel SE, Chen Z, Price M, Parker CS, Metlay JP, Christie JD, et al. The influence of patient adherence on anticoagulation control with warfarin. Arch Intern Med 2007;167:229-35.
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4. Waterman AD, Milligan PE, Bayer L, Banet GA, Gatchel SK, Gage BF. Effect of warfarin nonadherence on control of the international normalized ratio. Am J Health Syst Pharm 2004;61:1258-64. 5. Davis NJ, Billett HH, Cohen HW, Arnsten JH. Impact of adherence, knowledge, and quality of life in anticoagulation control. Ann Pharmacother 2005;39: 632-6. 6. Hu A, Chow CM, Dao D, Errett L, Keith M. Factors influencing patient knowledge of warfarin therapy after mechanical heart valve replacement. J Cardiovasc Nurs 2006;21:169-75. 7. McCormack P, Feely J, Hemeryck L, McCormack PME, Stinson JC. Audit of an anticoagulant clinic: doctor and patient knowledge. Ir Med J 1997;90:192-3. 8. Roche-Nagle G, Chambers F. Evaluation of patient knowledge regarding oral anticoagulants. Ir Med J 2003;96:211-3. 9. Nadar S, Begum N, Kaur B, Sandhu S, Lip GYH. Patients’ understanding of anticoagulant therapy in a multiethnic population. J R Soc Med 2003;96: 175-9. 10. Lane DA, Ponsford J, Shelley A, Sirpal A, Lip GYH. Patients’ knowledge and perceptions of atrial fibrillaton and anticoagulant therapy: effects of an educational intervention programme. Int J Cardiol 2006;110:354-8. 11. Tang EO, Lai CS, Lee KK, Wong RS, Cheng G, Chan TY. Relationship between patient’s warfarin knowledge and anticoagulation control. Ann Pharmacother 2003; 37:34-9. 12. Newcastle Anticoagulation Study Group. Effectiveness of anticoagulation among patients discharged from hospital on warfarin. Med J Aust 1998;169:243-6. 13. Zeolla MM, Brodeur MR, Dominelli A, Haines ST, Allie ND. Development and validation of an instrument to determine patient knowledge: the oral anticoagulation knowledge test. Ann Pharmacother 2006;40:633-8. 14. Briggs AL, Jackson TR, Bruce S, Shapiro NL. The development and performance validation of a tool to assess patients’ anticoagulation knowledge. Res Soc Admin Pharm 2005;1:40-59. 15. Wilson FL, Racine E, Tekiele V, Williams B. Literacy, readability and cultural barriers: critical factors to consider when educating older African Americans about anticoagulation therapy. J Clin Nurs 2003;12: 275-82. 16. Barcellona D, Contu P, Marongiu F. Patient education and oral anticoagulant therapy. Haematologica 2002; 87:1081-6.
17. Deschamps AE, De Geest S, Vandamme AM, Bobbaers H, Peetermans WE, Van Wijngaerden E. Diagnostic values of different adherence measures using electronic monitoring and virologic failure as reference standards. AIDS 2008;22:735-43. 18. Glass TR, De Geest S, Weber R, Vernazza PL, Rickenbach M, Furrer M, et al. Correlates of selfreported non-adherence to antiretroviral therapy in HIV-infected patients: the Swiss HIV Cohort Study. J Acquir Immune Defic Syndr 2006;41:385-92. 19. Casais P, Meschengieser SS, Sanchez-Luceros A, Lazzari MA. Patients’ perceptions regarding oral anticoagulation therapy and its effect on quality of life. Curr Med Res Opin 2005;21:1085-90. 20. Moons P, Engelfriet P, Kaemmerer H, Meijboom FJ, Oechslin E, Mulder BJM. Delivery of care for adult patients with congenital heart disease: results from the Euro Heart Survey. Eur Heart J 2006;27:1324-30. 21. Moons P, Scholte op Reimer W, De Geest S, Fridlund B, Heikkila J, Jaarsma T, et al. Nurse specialists in adult congenital heart disease: the current state in Europe. Eur J Cardiovasc Nurs 2006;5:60-7. 22. Porter B. The role of the advanced practice nurse in anticoagulation. AACN Clin Issues 2002;13:221-33. 23. Messick S. Validity of psychological assessment: validation of inferences from persons’ responses and performance as scientific inquiry into scoring meaning. Am Psychol 1995;9:741-9. 24. American Educational Research Association, American Psychological Association, National Council on Measurement in Education, Joint Committee on Standards for Educational and Psychological Testing, Standards for educational and psychological testing. Washington, DC: American Educational Research Association; 1999. 25. Goodwin LD. Changing conceptions of measurement validity: an update on the new standards. J Nurs Educ 2002;41:100-6. 26. Tashakkori A, Teddlie C. Handbook of mixed methods in social and behavioral research. Thousand Oaks: Sage Publications; 2003. 27. Strickland OL. When is internal consistency reliability assessment inappropriate? J Nurs Meas 1999;7:3-4. 28. Knapp TR, Kimble LP, Dunbar SB. Distinguishing between the stability of a construct and the stability of an instrument in trait/state measurement. Nurs Res 1998;47:60-2. 29. Moons P, Marquet K, Budts W, De Geest S. Validity, reliability and responsiveness of the Schedule for the Evaluation on Individual Quality of LifedDirect Weighting (SEIQoL-DW) in congenital heart disease. Health Qual Life Outcomes 2004;2:27.
Division of Congenital and Structural Cardiology, University Hospitals of Leuven, Leuven, Belgium, University Hospitals of Leuven, Leuven, Belgium b Department of Vascular Medicine and Hemostasis, University Hospitals of Leuven, Leuven, Belgium c Center for Health Services and Nursing Research, Katholieke Universiteit Leuven, Leuven, Belgium
article info
abstract
Article history: Received 25 September 2009 Revised 2 November 2009 Accepted 19 November 2009 Online 4 June 2010
Objective: This study sought to determine (1) the level of knowledge that mechanical heart-valve patients (because of congenital heart disease or acquired heart-valve defects) have about oral anticoagulation therapy; and (2) to what extent these patients adhere to this therapy.
Keywords: Knowledge Adherence Anticoagulation Heart defects Congenital Heart valve Nursing
Methods: This descriptive, cross-sectional study included 57 patients. Knowledge was measured using the Knowledge of Oral Anticoagulation Tool. Adherence was assessed with a visual analogue scale and the Swiss HIV Cohort Study Adherence Questionnaire. Results: Patients poorly understood symptoms relevant to over-anticoagulation and the effects of alcohol and vitamins on oral anticoagulants. The knowledge level of patients with congenital heart disease and acquired heart-valve defects did not differ significantly. Three-quarters of patients claimed to be 100% adherent to oral anticoagulant therapy. Conclusion: Most patients lack knowledge about oral anticoagulants, and one fourth of patients do not fully adhere to therapy. Cite this article: Van Damme, S., Van Deyk, K., Budts, W., Verhamme, P., & Moons, P. (2011, MARCH/ APRIL). Patient knowledge of and adherence to oral anticoagulation therapy after mechanical heart-valve replacement for congenital or acquired valve defects. Heart & Lung, 40(2), 139-146. doi:10.1016/ j.hrtlng.2009.11.005.
Lifelong treatment with oral anticoagulants is necessary in patients with 1 or more mechanical heart valves, to prevent cardioembolisms and preserve
adequate functioning of the mechanical heart valve.1 The use of oral anticoagulants is very complex, because of their narrow therapeutic range.2 Incorrect
* Corresponding author: Philip Moons, PhD, RN, Center for Health Services and Nursing Research, Katholieke Universiteit Leuven, Kapucijnenvoer 35, Postbox 7001, B-3000 Leuven, Belgium. E-mail address: [email protected] (P. Moons). 0147-9563/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.hrtlng.2009.11.005
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use can lead to life-threatening bleeding, on the one hand, or catastrophic thromboembolisms, on the other. Previous studies showed that patient compliance is crucial in adequate anticoagulation therapy.3,4 The cohort study of Waterman et al showed that 23% of all international normalized ratio (INR) values for the anticoagulant warfarin were outside the target range.4 Thirty-six percent of these values could be explained by changes in the patient’s eating behavior, misunderstanding of the drug dose, skipping a dose, missing consultations in an outpatient clinic, excessive consumption of alcohol, or failure to obtain timely and correct prescriptions.4 These findings suggest that successful therapy depends on a patient’s understanding of the treatment. However, patients’ knowledge of oral anticoagulation therapy is lacking. Some studies found that more than half of patients on anticoagulants had poor knowledge of the therapy.5-10 One study reported that 63% of patients did not know the correct dose of their medication.7 Another study found that 60% of patients could not list the potential side effects of overdosing or underdosing, and that 28% of patients did not know why they had to take anticoagulants.8 In other studies, 43% to 46% of patients did not know why they had to take anticoagulants.9,10 Some investigations explored the possible relationship between knowledge of, and adherence to, anticoagulation therapy. One study found a positive correlation between patients’ knowledge of oral anticoagulation therapy and the total number of INRs within the target range.11 Other studies, however, failed to find such a relationship.5,12 Moreover, most investigations did not focus on patients with a mechanical heart valve, but recruited a range of patients on anticoagulants. To date, no study has reported on mechanical heart-valve patients who received their valves because of a congenital heartvalve defect. Therefore, the present study sought to (1) assess the level of knowledge that mechanical heart-valve patients possess about oral anticoagulation therapy (only patients with congenital heart disease [CHD] or acquired heart-valve defects [AHDs] were studied); (2) determine to what extent these patients adhered to oral anticoagulation therapy; and (3) compare the knowledge and adherence of CHD and AHD patients.
Methods Study Population We used a descriptive, cross-sectional design. Patients were included if they were aged 18 years or older, if they were Dutch-speaking and literate, and if they had a mechanical heart valve because of CHD or an AHD.
Congenital heart disease patients were recruited from the computerized database of a Pediatric and Adult Congenital Heart Disease Program at an institution in Belgium. Patients with acquired heart-valve defects were eligible if they were undergoing regular follow-up for INR control at the University Hospitals Leuven, or if they were managed by a general practitioner and their blood samples for INR control were analyzed at the aforementioned university hospitals. Patients were excluded if they manifested mental retardation. Sixty-one patients met the inclusion criteria: 28 had CHD, and 33 had AHDs. Three patients refused participation, and 1 completed form was lost in the mail. Hence, 57 patients (93%) participated: 25 with CHD, and 32 with AHDs.
Variables and Measurements Demographic and Clinical Variables Demographic variables included gender and age. Clinical variables included primary diagnosis, type of mechanical heart valve, kind of oral anticoagulating drug, duration of therapy, type of follow-up, and frequency of INR control measurements. These variables were collected from patients’ medical records.
Knowledge We conducted a comprehensive literature search for an appropriate instrument to evaluate patients’ knowledge of oral anticoagulants. Eight questionnaires were identified.5,6,9-11,13-16 These questionnaires differed in layout, number of items, and aspects of knowledge. Only 3 of 8 instruments were evaluated for validity and reliability.13-15 However, none of these questionnaires was appropriate for the present study, because of length or difficulties with translation. Therefore, we developed a new questionnaire for patients with either CHD or AHDs. Five different knowledge domains dealt with oral anticoagulant treatments: (1) general information about the functioning of the medication, (2) possible side effects, (3) interactions with ingested food, (4) interactions with other medications, and (5) lifestyle.5,9-11,13,14,16 We developed a questionnaire comprising 10 multiple-choice questions, including 2 questions for each of the 5 knowledge domains. For each question, 4 possible answers were given, 1 of which was correct. To avoid wild guesses, we included as a possible answer, “I don’t know.”5 Thus, in the datacoding process, the patient’s answers could be evaluated as “right,” “wrong,” or “I don’t know.” A panel of 5 experts in oral anticoagulation medication evaluated the content validity of the newly developed questionnaire. They assessed the knowledge questionnaire according to form, content, and legibility. To evaluate the legibility and intelligibility of the questions (face validity), we performed a small pilot study with 3 patients who recently started oral anticoagulant therapy. On the basis of comments from experts and patients, we adjusted the knowledge
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questionnaire. The final questionnaire was called the Knowledge of Oral Anticoagulation Tool (KOAT). The full version of the instrument can be requested from the authors.
Results
Adherence
Demographic and clinical variables are shown in Table 1. The sample comprised 57 respondents: 35 were male, and 22 were female. The median age was 60 years. The aortic valve was the most frequently replaced heart valve in this study population. Fenprocoumon was the most commonly taken oral anticoagulant. The median duration of anticoagulation therapy was 10 years. The most prevalent heart defects in patients with CHD were congenital aortic stenosis (n ¼ 6; 24%), coarctation of the aorta (n ¼ 5; 20%), an Ebstein anomaly (n ¼ 3; 12%), and ventricular septal defects (n ¼ 3; 12%). Patients with AHDs were significantly older than patients with CHD (Table 1).
To evaluate patients’ adherence to anticoagulation treatment, we used 2 self-report questionnaires: the visual analogue scale (VAS) and the Swiss HIV Cohort Study Adherence Questionnaire (SHCS-AQ). The VAS scale is a horizontal line, ranging from 0% to 100%, on which respondents can indicate the percentage of prescribed doses they have actually taken over the last month. Hence, the VAS measures dosing adherence. The SHCS-AQ questionnaire measures drug-taking adherence and drug holidays. This questionnaire comprises 2 questions: “How often did you miss 1 dose of the medication in the last month?” and “Did you have a period of no drug intake for more than 24 hours in the last 4 weeks?” Previous studies suggest that both the VAS and SHCS-AQ demonstrate good psychometric properties.17,18 However, these questionnaires were not evaluated for use in patients on oral anticoagulation therapy.
Procedure The set of questionnaires was sent to all patients who met the inclusion criteria. An accompanying letter explained the goal and procedure of the study. Completing the questionnaires took about 15 minutes. The completed questionnaires could be returned in a preaddressed, prestamped envelope. If questionnaires were not returned within 2 months, the patient received a follow-up telephone call. Informed consent was assumed if the patient completed the questionnaires. After completing the study, every participant received the correct answers by mail as a feedback instruction. The study was approved by the Institutional Review Board of the aforementioned institution in Belgium.
Statistical Analysis Descriptive statistics for nominal and ordinal variables were expressed in percentages. Medians, quartiles, and ranges were calculated for continuous, non-normally distributed data. To test differences between the CHD and AHD groups, the c2 test and Fisher’s exact test were used for nominal-level data, and the MannWhitney U test was used for ordinal-level or continuous-level data. A possible relationship between knowledge and adherence was explored using binary logistic regression. The level of significance was set at P < .05. Data were analyzed using the Statistical Package of the Social Sciences, version 12.0 (SPSS, Inc., Chicago, IL).
Sample Characteristics
Knowledge The median total score on the knowledge questionnaire was 7 on a scale of 0 to 10. Nine patients (15.7%) answered more than 8 questions correctly, 45 patients (78.9%) answered between 5 and 8 questions correctly, and 3 patients (5.2%) answered fewer than 5 questions correctly. The median total score of CHD and AHD patients was 7. Almost all patients (94.7% and 98.2% of CHD and AHD patients, respectively) provided correct answers for questions regarding the name of the blood-clotting test and the effect of their oral anticoagulation medication (Table 2). More than 80% of respondents (87.7% and 80.7% of CHD and AHD patients, respectively) knew that their medication should be stopped a few days before certain surgical interventions, and that forgetting a dose of the medication increased the risk for thromboembolism. Furthermore, 75.4% of patients correctly listed paracetamol as a medicine that can be taken for headaches; 70.2% designated contact sports (such as horseback riding, judo, and football) as sports to avoid during the use of oral anticoagulation medication; and 61.4% knew what to do when a dose of the medication was missed. Less than half (43.9%) of the study sample knew that black-colored stools are an indicator that something is wrong with the concentration of medication in the blood; 43.9% knew that more than 2 consumptions of alcohol can thin the blood; and 21.1% knew that certain vitamins (eg, vitamin K) can influence their medication. When stratifying subjects according to CHD and AHD, more CHD patients knew the correct answers on questions about the influence of alcohol (56% vs 34.4% of CHD and AHD patients, respectively) and vitamin preparations (28% vs 15.6% of CHD and AHD patients, respectively). On the other hand, more AHD patients correctly answered the question regarding what medication was allowed for headaches (81.3% vs 68% of AHD and CHD patients, respectively), and the question
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Table 1 e Demographic and clinical variables of 57 patients with a mechanical heart valve Variables Age (y) Median (Q1; Q3) Range Gender, n (%) Female Male Duration of therapy with oral anticoagulants (y) Median (Q1; Q3) Range Heart valve replaced by a mechanical valve, n (%) Aortic Mitral Tricuspid Aortic and mitral Aortic, mitral, and tricuspid Type of follow-up, n (%) General practitioner Hospital Self-management Family member Type of oral anticoagulant, n (%) Fenprocoumon Acenocoumarol Frequency of follow-up, n (%) 2 weeks Every 3 weeks Every 4 weeks 5 weeks
All patients (n ¼ 57)
Congenital heart disease (n ¼ 25)
Acquired valve defects (n ¼ 32)
60 (Q1 ¼ 44; Q3 ¼ 69) 18-82
43 (Q1 ¼ 27; Q3 ¼ 50) 18-60
66.5 (Q1 ¼ 62; Q3 ¼ 74.7) 54-82
22 (38.6) 35 (61.4)
9 (36) 16 (64)
13 (40.6) 19 (59.4)
Test value P values U ¼ 10.500 P < .001 c2 ¼ .127 P ¼ .722 U ¼ 282.500
10 (Q1 ¼ 6; Q3 ¼ 22) .6-32
8 (Q1 ¼ 5; Q3 ¼ 19.125) 2-32
17 (Q1 ¼ 27; Q3 ¼ 24.75) .6-32
P ¼ .092 FE ¼ 7.993
35 (61.3) 13 (22.8) 3 (5.3) 5 (8.8) 1 (1.8)
16 (64) 6 (24) 3 (12) 0 (0) 0 (0)
19 (59.4) 7 (21.9) 0 (0) 5 (15.6) 1 (3.1)
34 (59.6) 19 (33.3) 3 (5.3) 1 (1.8)
21 (84) 0 (0) 3 (12) 1 (4)
13 (40.6) 19 (59.6) 0 (0) 0 (0)
56 (98.2) 1 (1.8)
24 (96) 1 (4)
33 (100) 0 (0)
6 (10.5) 12 (21.1) 35 (61.4) 4 (7)
3 (12) 6 (24) 14 (56) 2 (8)
3 (9.4) 6 (18.8) 21 (65.4) 2 (6.3)
P ¼ .053
FE ¼ 27.536 P < .001
FE* P ¼ .439 FE ¼ .822 P ¼ .913
Q1, first quartile; Q3, third quartile; INR, international normalized ratio; FE, Fisher’s exact test; U, Man-Whitney U test. * Fisher’s exact test value was not provided.
regarding the issue of the need to stop their medication a few days before a surgical intervention (93.8% vs 80% of AHD and CHD patients, respectively). However, statistical significance between groups was not achieved (Table 2).
Adherence On the VAS, 72.2% of patients indicated that they were 100% adherent. On the SHCS-AQ, 75% stated that they had not missed 1 dose of their medication during the last month. Of the remaining patients, 14.3% missed 1 dose during the last month, 7.1% missed 1 dose in the preceding 14 days, and 3.6% missed 1 dose during the last week. No patients reported a drug holiday, which was defined as missing 2 consecutive doses
Relationship Between Knowledge and Adherence No statistically significant association between any knowledge item and the VAS on adherence was found.
Discussion Patients’ knowledge of, and adherence to, oral anticoagulation medication therapy play a pivotal role in the prevention of life-threatening complications. The risk for bleeding or thromboembolisms increases with incorrect use.5,19 Despite these facts, previous studies demonstrated that knowledge and adherence in this patient population are often insufficient.3-10 Previous studies assessed only patients with acquired valve defects. Using a newly developed questionnaire, we investigated knowledge of and adherence to oral anticoagulation medication in congenital or acquired valve-disease patients who had one or more mechanical heart valves. Patients possessed much knowledge (ie, >80% of patients provided the correct answer) about the name of the blood-clotting test, the effect of their oral anticoagulation medication, the increased risk for developing thromboembolisms when a dose of the medication was missed, and the need to stop their medication a few days before certain surgical interventions. Patients
Table 2 e Distribution of answers to knowledge of oral anticoagulation tool n (%)
All patients (n ¼ 57) Right
I don’t know
Right
Wrong
Acquired valve defects (n ¼ 32)
I don’t know
Right
Wrong
I don’t know
Test value and P value
54 (94.7)
0 (0)
3 (5.3)
23 (92)
0 (0)
2 (8.0)
31 (96.9)
0 (0)
1 (3.1)
c2 ¼ .669 P ¼ .413
56 (98.2)
0 (0)
1 (1.8)
24 (96)
0 (0)
1 (4.0)
32 (100)
0 (0)
0 (0)
25 (43.9)
6 (10.5)
26 (45.6)
12 (48)
4 (16.0)
9 (36.0)
13 (40.6)
2 (6.2)
17 (53.1)
c2 ¼ 1.303 P ¼ .254 c2 ¼ .310 P ¼ .578
46 (80.7)
7 (12.3)
4 (7.0)
21 (84)
3 (12.0)
1 (4.0)
25 (78.1)
4 (12.5)
3 (9.4)
25 (43.9)
21 (36.8)
11 (19.3)
14 (56)
6 (24.0)
5 (20.0)
11 (34.4)
15 (46.9)
6 (18.8)
12 (21.1)
13 (22.8)
32 (56.1)
7 (28)
6 (24.0)
12 (48.0)
5 (15.6)
7 (21.9)
20 (62.5)
43 (75.4)
13 (22.8)
1 (1.8)
17 (68)
8 (32.0)
0 (0)
26 (81.3)
5 (15.6)
1 (3.1)
40 (70.2)
1 (1.8)
16 (28.1)
18 (72)
0 (0)
7 (28.0)
22 (68.8)
1 (3.1)
9 (28.1)
50 (87.7)
2 (3.5)
5 (8.8)
20 (80)
1 (4.0)
4 (16.0)
30 (93.8)
1 (3.1)
1 (3.1)
35 (61.4)
16 (28.1)
6 (10.5)
15 (60)
8 (32.0)
2 (8.0)
20 (62.5)
8 (25.0)
4 (12.5)
c2 ¼ .311 P ¼ .577 c2 ¼ 2.666 P ¼ .103 c2 ¼ 1.293 P ¼ .255 c2 ¼ 1.330 P ¼ .249 c2 ¼ .071 P ¼ .790 c2 ¼ 2.463 P ¼ .117 c2 ¼ .037 P ¼ .847
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1. What kind of blood test can be performed to evaluate the effectiveness of oral anticoagulating medication? 2. What is the effect of oral anticoagulating medication? 3. What complaint could indicate that there is something wrong with the amount of medication in the blood? 4. What are the consequences when a person forgets a dose of the medication? 5. Drinking more than 2 drinks of alcohol during a party, may cause ____. 6. Which of the following products can possibly have an effect on the amount of medication in the blood? 7. What kind of medication are you allowed to take in case of headache? 8. Which of the following sports should be avoided? 9. What should you do with the oral anticoagulating medication in case of surgery? 10. What do you do when you forget a dose of the medication and you notice it the next day?
Wrong
Congenital heart disease (n ¼ 25)
143
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displayed moderate knowledge (50% to 80% correct answers) about what kind of medication can be taken for headaches, what kind of sports should be avoided, and what to do when a dose of the medication was missed. Patients exhibited poor knowledge (<50% correct answers) about symptoms that indicate a problem with the level of medication in their blood, the blood-thinning effect of alcohol, and the influence of certain vitamins on their medication. Although not statistically significant, differences in the level of knowledge between CHD and AHD patients were evident for some questions. Comparing the results of our study with those of previous investigations revealed similarities. We corroborated the finding that patients have much knowledge about the effects of anticoagulants,9 but moderate to poor knowledge about interactions between food or vitamin products and oral anticoagulation medications.6,10,11 On the other hand, more patients in our study (61.4%) correctly answered the question of what to do when a dose of the medication was missed, than did patients (35%) in the study of Tang et al.11 In general, overall knowledge scores in previous studies were lower than those in our investigation.5,11 We found that three quarters of the patients were 100% adherent to their medication therapy. No difference was evident for median total scores between CHD and AHD patients. No statistically significant relationship was found between knowledge and adherence. The level of adherence was substantially better in our study than in that of Davis et al,5 who found only 50% of patients to be fully adherent. In another study, knowledge of oral anticoagulation level and INR values positively correlated with the target range.11 The results of different studies, however, cannot be compared, because different methods were used to measure adherence. Our results demonstrate that structured educational interventions should be used to improve the level of knowledge in patients on oral anticoagulation medications. In addition, adherence-improving strategies should be implemented to target the one quarter of patients who reported nonadherence. Nurses can play a pivotal role in the implementation of educational and adherence-promoting interventions. Indeed, the growing number of advanced-practice nurses for congenital heart disease20,21 or specialized anticoagulation services22 results in a workforce that is trained and dedicated to take on this role. Only 3 of 57 participating patients were under selfmanagement. At the time of our study (2007 and 2008), the reimbursement system in Belgium did not reimburse patients for buying point-of-care equipment for checking INRs. On the other hand, blood checks by general practitioners or hospitals were to a large extent reimbursed by the compulsory health-insurance system. Such a system discourages patients to check their INR themselves. New regulations are in progress in Belgium. Hence, the number of patients under
self-control and self-management will increase in the future.
Clinimetric Aspects of the KOAT Before an instrument can be used in research or clinical practice, aspects of its validity, reliability, and responsiveness should be evaluated. The traditional views focusing on content, criterion-related, and construct validity are no longer appropriate,23 and pose significant challenges to instruments that assess levels of knowledge in individuals. Therefore, the standards for educational and psychological testing, as developed by the American Educational Research Association; American Psychological Association, National Council on Measurement in Education, and Joint Committee on Standards for Educational and Psychological Testing, are more applicable in evaluating the clinimetric properties of the KOAT.24 Standards for educational and psychological testing consider validity as a unitary concept, for which evidence along 5 lines has to be accumulated: evidence based on test content, internal structure, relationship with other variables, response processes, and consequences of testing.24 Evidence based on test content refers to the themes, wording, and format of the questions of an instrument, as well as the guidelines for procedures regarding administration and scoring.24 With respect to KOAT, we evaluated test content by forming a panel of 5 experts in oral anticoagulation medication to assess the form, content, and legibility of KOAT. Furthermore, 3 patients were asked to appraise the legibility and intelligibility of the questions. On the basis of comments from experts and patients, we adjusted the questionnaire. Additional evidence regarding test content was derived from completed questionnaires. We found that no data were missing in the KOAT. This finding suggests sufficient comprehension of the items, attainable data within the context of care, and construct relevance.25 Analysis of the internal structure of a test indicates the degree to which the relationship among items and components conforms to the construct as operationally defined.24 Evidence on internal structure can be provided by factor analysis. For instance, it could be useful to investigate whether the 5 different knowledge domains (ie, functioning of the medication, possible side effects, interactions with ingested food, interactions with other medication, and lifestyle) are identifiable in 5 factors. Factor analysis, however, was not feasible for the data in the present study because of the limited sample size and non-normal distribution of data. Evidence for the relationship with other variables corresponded with the association between test scores and other variables that the test was expected to correlate with or predict.24 In this respect, the scores on the instrument under study are compared with those of a gold standard. With respect to the assessment of level of knowledge, there is no gold standard.
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In addition, existing questionnaires were not appropriate for use in the present study. This was precisely the rationale for developing the KOAT. Thus, we could not use another knowledge instrument in our study to compare with KOAT scores. Evidence based on response processes refers to the question, “To what extent does the type of performances or responses in which examinees engage fit the intended construct?”25 This can be investigated by undertaking interviews or focus groups with respondents to determine the reasons for providing certain answers to questions. In other words, a sequential quan-qual design is needed to provide evidence on response processes.26 Including evidence on the consequences of testing is a relatively new concept. It pertains to the benefits or negative consequences of a test. For this purpose, both researchers and respondents can be interviewed. The objective of our project was to improve the educational care of our patients. Hence, no specific negative consequences of the test were anticipated. On the contrary, we provided feedback to respondents, to educate them about different aspects of anticoagulation therapy. Evidence based on reliability refers to the internal consistency, interrater reliability, and stability of an instrument. The reliability of internal consistency may be assessed by calculating Cronbach’s a for the items of KOAT. However, the calculation of Cronbach’s a is only useful if the items on a scale are conceptually related to each other.27 The items in KOAT are deliberately and appropriately not homogeneous. For instance, knowing the function of anticoagulation is not necessarily related to a knowledge of interactions with ingested food. Therefore, the calculation of an a-coefficient for KOAT is not useful.27 Moreover, the assessment of interrater reliability of KOAT is irrelevant, because it is a self-report instrument. Testing the stability of this instrument is possible. However, a traditional test-retest approach cannot be used. Knowledge can change over time, and is therefore not a stable construct. Hence, the application of a strategy is imperative in which the stability of a construct (knowledge) and the stability of a tool (KOAT) can be distinguished. Such a method was described by Knapp et al, but requires at least 3, and preferably 4, consecutive measurements.28 Because 4 measurements were not possible within the time frame of the project, we refrained from testing the stability of the KOAT. Evidence based on responsiveness refers to the ability of an instrument to detect clinically important changes.29 Responsiveness can be explored by examining changes in scores before and after the implementation of an educational program. We are considering such a project in the future. In addition, responsiveness can be tested by identifying floor and ceiling effects of the instrument. As indicated in Table 2, responses on the items of KOAT were welldistributed, suggesting that this instrument does not exhibit floor or ceiling effects.
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Methodological Limitations The results of the present study should be interpreted with caution because of some methodological limitations. First, although we had an attrition rate of only 7%, the sample in our study was rather small. Therefore, our results cannot be generalized to the entire population of patients with mechanical heart valves and anticoagulating drugs. Second, we had to devise a new instrument to measure knowledge, because existing questionnaires were not applicable. The first evidence of the validity and responsiveness of KOAT was established. However, other clinimetric aspects of KOAT should be scrutinized in future research. To measure adherence, we used a VAS and the SHCS-AQ. The SHCS-AQ was initially developed for HIV patients. Although we cannot transfer the questionnaire to other patient populations as such, adherence to medication in patients with mechanical heart valves is as critically important as in HIV patients. Therefore, we assumed that this questionnaire would be appropriate for our purpose. Future studies should validate these measurements in anticoagulation therapy.
Conclusions We investigated patient knowledge of, and adherence to, anticoagulation therapy in patients with 1 or more mechanical heart valves implanted because of a CHD or a noncongenital heart disease. A new questionnaire, called KOAT, was developed for this study. Moderate to poor knowledge was evident for the kinds of medication that can be taken in case of headaches, the sports to be avoided, what to do when a dose of medication is forgotten, symptoms that can indicate a problem with the level of medication in the blood, the blood-thinning effect of alcohol, and the influence of certain vitamins on medications. One quarter of the patients admitted to less than full adherence. These findings indicate that room exists for structured educational interventions and adherence-promoting strategies.
References 1. Koertke H, Zitterman A, Tenderich G, Wagner O, ElArousy M, Krian A, et al. Low-dose oral anticoagulation in patients with mechanical heart valve prostheses: final report from the early selfmanagement anticoagulation trial III. Eur Heart J 2007; 28:2479-84. 2. Ufer M. Comparative pharmacokinetics of vitamin K antagonists. Clin Pharmacokinet 2005;44:1227-46. 3. Kimmel SE, Chen Z, Price M, Parker CS, Metlay JP, Christie JD, et al. The influence of patient adherence on anticoagulation control with warfarin. Arch Intern Med 2007;167:229-35.
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4. Waterman AD, Milligan PE, Bayer L, Banet GA, Gatchel SK, Gage BF. Effect of warfarin nonadherence on control of the international normalized ratio. Am J Health Syst Pharm 2004;61:1258-64. 5. Davis NJ, Billett HH, Cohen HW, Arnsten JH. Impact of adherence, knowledge, and quality of life in anticoagulation control. Ann Pharmacother 2005;39: 632-6. 6. Hu A, Chow CM, Dao D, Errett L, Keith M. Factors influencing patient knowledge of warfarin therapy after mechanical heart valve replacement. J Cardiovasc Nurs 2006;21:169-75. 7. McCormack P, Feely J, Hemeryck L, McCormack PME, Stinson JC. Audit of an anticoagulant clinic: doctor and patient knowledge. Ir Med J 1997;90:192-3. 8. Roche-Nagle G, Chambers F. Evaluation of patient knowledge regarding oral anticoagulants. Ir Med J 2003;96:211-3. 9. Nadar S, Begum N, Kaur B, Sandhu S, Lip GYH. Patients’ understanding of anticoagulant therapy in a multiethnic population. J R Soc Med 2003;96: 175-9. 10. Lane DA, Ponsford J, Shelley A, Sirpal A, Lip GYH. Patients’ knowledge and perceptions of atrial fibrillaton and anticoagulant therapy: effects of an educational intervention programme. Int J Cardiol 2006;110:354-8. 11. Tang EO, Lai CS, Lee KK, Wong RS, Cheng G, Chan TY. Relationship between patient’s warfarin knowledge and anticoagulation control. Ann Pharmacother 2003; 37:34-9. 12. Newcastle Anticoagulation Study Group. Effectiveness of anticoagulation among patients discharged from hospital on warfarin. Med J Aust 1998;169:243-6. 13. Zeolla MM, Brodeur MR, Dominelli A, Haines ST, Allie ND. Development and validation of an instrument to determine patient knowledge: the oral anticoagulation knowledge test. Ann Pharmacother 2006;40:633-8. 14. Briggs AL, Jackson TR, Bruce S, Shapiro NL. The development and performance validation of a tool to assess patients’ anticoagulation knowledge. Res Soc Admin Pharm 2005;1:40-59. 15. Wilson FL, Racine E, Tekiele V, Williams B. Literacy, readability and cultural barriers: critical factors to consider when educating older African Americans about anticoagulation therapy. J Clin Nurs 2003;12: 275-82. 16. Barcellona D, Contu P, Marongiu F. Patient education and oral anticoagulant therapy. Haematologica 2002; 87:1081-6.
17. Deschamps AE, De Geest S, Vandamme AM, Bobbaers H, Peetermans WE, Van Wijngaerden E. Diagnostic values of different adherence measures using electronic monitoring and virologic failure as reference standards. AIDS 2008;22:735-43. 18. Glass TR, De Geest S, Weber R, Vernazza PL, Rickenbach M, Furrer M, et al. Correlates of selfreported non-adherence to antiretroviral therapy in HIV-infected patients: the Swiss HIV Cohort Study. J Acquir Immune Defic Syndr 2006;41:385-92. 19. Casais P, Meschengieser SS, Sanchez-Luceros A, Lazzari MA. Patients’ perceptions regarding oral anticoagulation therapy and its effect on quality of life. Curr Med Res Opin 2005;21:1085-90. 20. Moons P, Engelfriet P, Kaemmerer H, Meijboom FJ, Oechslin E, Mulder BJM. Delivery of care for adult patients with congenital heart disease: results from the Euro Heart Survey. Eur Heart J 2006;27:1324-30. 21. Moons P, Scholte op Reimer W, De Geest S, Fridlund B, Heikkila J, Jaarsma T, et al. Nurse specialists in adult congenital heart disease: the current state in Europe. Eur J Cardiovasc Nurs 2006;5:60-7. 22. Porter B. The role of the advanced practice nurse in anticoagulation. AACN Clin Issues 2002;13:221-33. 23. Messick S. Validity of psychological assessment: validation of inferences from persons’ responses and performance as scientific inquiry into scoring meaning. Am Psychol 1995;9:741-9. 24. American Educational Research Association, American Psychological Association, National Council on Measurement in Education, Joint Committee on Standards for Educational and Psychological Testing, Standards for educational and psychological testing. Washington, DC: American Educational Research Association; 1999. 25. Goodwin LD. Changing conceptions of measurement validity: an update on the new standards. J Nurs Educ 2002;41:100-6. 26. Tashakkori A, Teddlie C. Handbook of mixed methods in social and behavioral research. Thousand Oaks: Sage Publications; 2003. 27. Strickland OL. When is internal consistency reliability assessment inappropriate? J Nurs Meas 1999;7:3-4. 28. Knapp TR, Kimble LP, Dunbar SB. Distinguishing between the stability of a construct and the stability of an instrument in trait/state measurement. Nurs Res 1998;47:60-2. 29. Moons P, Marquet K, Budts W, De Geest S. Validity, reliability and responsiveness of the Schedule for the Evaluation on Individual Quality of LifedDirect Weighting (SEIQoL-DW) in congenital heart disease. Health Qual Life Outcomes 2004;2:27.