- Email: [email protected]
Newest Vital Sign as a proxy for medication adherence in older adults
RESEARCH
Newest Vital Sign as a proxy for medication adherence in older adults Teresa M. Salgado, Sara B. Ramos, Clésia Sobreira, Rita Canas, Inês Cunha, Shalom I. Benrimoj, and Fernando Fernandez-Llimos
Received December 28, 2012, and in revised form May 20, 2013. Accepted for publication June 18, 2013.
Abstract Objective: To assess the utility of the Newest Vital Sign (NVS) as a proxy for medication adherence in community-dwelling older adults. Design: Descriptive cross-sectional study. Setting: 12 adult day care centers in the Lisbon metropolitan area, Portugal, between March and May 2009. Participants: 100 white community-dwelling older adults. Intervention: Participants were administered the NVS, Single Item Literacy Screener (SILS), and self-reported Measure of Adherence to Therapy (MAT). Main outcome measures: Health literacy and medication adherence. Results: The mean (±SD) age of the respondents was 73.3 ± 7.8 years and 71% were women. The NVS score was 0.81 ± 0.10 (of 6 possible points), and 95% of the respondents scored in the three lowest possible scores, indicating a notable floor effect. Age was found to be inversely correlated with NVS score (P = 0.003). The MAT score was 36.2 ± 4.7 (range 17–42). No statistically significant association between the NVS and level of education (P = 0.059 [Kruskal–Wallis]), gender (P = 0.700 [Mann–Whitney]), SILS (P = 0.167), or MAT (P = 0.379) was identified. Conclusion: The utility of the NVS as a proxy for medication adherence in community-dwelling older adults is limited because of a floor effect that hinders its predictive power for medication adherence.
Teresa M. Salgado, MSc(Pharm), is a PhD candidate; Sara B. Ramos, MSc(Pharm) is a graduate student; Clésia Sobreira, MSc(Pharm) is a graduate student; Rita Canas, MSc(Pharm) is a graduate student; and Inês Cunha, MSc(Pharm) is a graduate student, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal. Shalom I. Benrimoj, PhD, is Head, Graduate School of Health, University of Technology, Sydney, Australia. Fernando FernandezLlimos, PhD, MBA, is Assistant Professor, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal. Correspondence: Fernando FernandezLlimos, PhD, MBA, Faculdade de Farmacia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. E-mail: [email protected] Disclosure: Ms. Salgado received a doctoral grant from the Portuguese Ministry of Education and Science. The other authors declare no conflicts of interest or financial interests in any product or service mentioned in this article, including grants, employment, gifts, stock holdings, or honoraria. Funding: Foundation for Science and Technology, Ministry of Education and Science, Portugal (doctoral grant no. SFRH/ BD/43999/2008).
Keywords: Adherence (medication), floor effect, health literacy, Newest Vital Sign, older patients.
Previous presentation: 41st European Society of Clinical Pharmacy Symposium on Clinical Pharmacy, October 28–31, 2012, Barcelona, Spain.
J Am Pharm Assoc. 2013;53:611–617. doi: 10.1331/JAPhA.2013.12249
Published online ahead of print at www. japha.org on October 4, 2013.
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H
ealth literacy was defined by the Institute of Medicine as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions.”1 Health literacy is a multifaceted concept2 that has evolved from the basic skills of reading and numeracy to critical thinking, problem solving, decision making, information seeking, and communication.3 Several instruments therefore have been developed to assess health literacy,4–9 and the Newest Vital Sign (NVS) is one of the most frequently used. However, none of these instruments fully grasps the concept of health literacy in terms of language, context, culture, communication, and technology.3 In addition, when comparing the performance of three of these instruments, they appear to measure different though related constructs.10 As medication information providers, pharmacists should be aware of patients’ health literacy level11,12 and tailor medication counseling to their needs.13 Inadequate health literacy can mean greater misunderstanding of drug information14,15 and lower medication management capacity.16,17 Low health literacy has been associated with poor health outcomes in conditions such as diabetes,18 chronic kidney disease,19 human immunodeficiency virus/acquired immunodeficiency syndrome,16 cancer,20 and asthma.21 Other studies revealed that patients with inadequate health literacy presented an increased risk of hospital admissions,22 less knowledge about their health
At a Glance Synopsis: This study assessed the utility of Newest Vital Sign (NVS)—one of the most frequently used health literacy assessment tools—as a proxy for medication adherence in community-dwelling older adults. The older adults in the current study performed poorly on the NVS, resulting in a floor effect in the health literacy score distribution that hinders the NVS’s predictive power for medication adherence. These results indicate that the NVS is not useful in screening older adults for low health literacy and does not have utility as a proxy for medication adherence. Analysis: Evidence has indicated that although the NVS has high sensitivity in younger people, it may not be suitable for older adults. Further development and refinement of health literacy instruments use among older adults is required. Assessing “medication literacy” specifically instead of complete functional health literacy may help pharmacists provide more tailored patient counseling to older people. New instruments that are designed to address specific patient characteristics should result in improved counseling and better medication adherence.
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problems,23,24 and higher health care costs.25,26 Conversely, some studies failed to demonstrate a significant association between health literacy and several clinical outcomes.27,28 Conflicting evidence exists for the relationship between health literacy and adherence, with some studies reporting no association29,30 and others showing a link between lower literacy and poorer adherence.31,32 Age and health literacy are inversely correlated.10,18,33–36 Assessing health literacy in older patients is extremely relevant because of the high prevalence of polypharmacy in this population, as shown by studies conducted in hospitals,37 nursing homes,38 and the community.39 Complex drug regimens and the technical communication frequently used by health professionals40 may cause older patients to be more prone to misunderstandings and subsequent drug use problems, which likely are exacerbated by inadequate health literacy. Further, limited literacy has been associated with increased mortality in older patients.41,42 The NVS has been described as a health literacy assessment tool with high sensitivity43 and short administration time.9 However, the NVS was originally validated in a relatively young population (mean age 41.3 years).9 The relationship between health literacy and medication adherence remains unclear, and few studies have evaluated the performance of health literacy instruments in older patients.44
Objective The aim of our study was to assess the utility of the NVS as a proxy for medication adherence in communitydwelling older adults.
Methods This cross-sectional study was conducted between March and May 2009. Ethics approval was granted by the Clinical Research Ethics Committee of the Faculty of Pharmacy, University of Lisbon (resolution no. 01/ CEECFFUL/2012). The study enrolled older adults attending 12 adult day care centers in Amadora, an urban municipality of the Lisbon metropolitan area in Portugal. Adult day care centers in Portugal are facilities at which older people get together, eat meals (e.g., breakfast, lunch, afternoon tea), and participate in leisure activities. Most of the people who attend these centers are fully functional and independent individuals who are responsible for managing their medications. This study was part of a broader investigation about medication follow-up. The recruitment was performed by approaching individuals attending adult day care centers, and those who agreed to participate were included in the study. No age restrictions were applied. To identify and exclude people with cognitive impairment, individuals were asked the date (month and year) and name of the adult day care center at which the study was taking place as a screening question. Considering a Journal of the American Pharmacists Association
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prevalence of 85% low literacy in older individuals,45,46 a CI of 95%, and the size of the Portuguese population older than 65 years (n = 1,874,209),47 the margin of error estimated for a sample size of 100 individuals was 7.0%. Before being invited to participate, potential respondents were informed about the objectives and methodology of the study and ensured that their anonymity would be preserved throughout the process. Individuals were free to withdraw at any time without further explanation, and no coercion to consent occurred. Individuals who agreed to participate gave their verbal consent and were subsequently administered three questionnaires: the NVS,9 Single Item Literacy Screener (SILS),48 and a previously validated Portuguese self-reported measure (Measure of Adherence to Therapy [MAT]).49 The questionnaires were administered by a member of the research team in the form of a structured interview. Sociodemographic data such as age, gender, and level of education also were collected. Study instruments The NVS is a six-question assessment based on an ice cream nutrition facts label that assesses numeracy skills, locate-the-information skills, and abstract reasoning skills. The final score is obtained through the number of correct and incorrect answers, with scores ranging from 0 to 6. Scores between 4 and 6 indicate sufficient health literate, 2 and 3 possible limited literacy, and 0 or 1 high likelihood (≥50%) of limited literacy.9 The original English version of the NVS was independently translated into Portuguese by members of the research team who were fluent in both languages. A consensual translated version was achieved following thorough discussion within the research team. Portuguese nutrition facts labels are similar to U.S. labels; therefore, we were able to maintain the structure of the original version of the instrument to enable international comparisons. This also has been reported in a previous European study.50 Assessments of the reliability and validity of the instrument were beyond the scope of this study. The SILS, which consists of a single question (“How often do you need to have someone help you when you read instructions, pamphlets, or other written material from your physician or pharmacy?”), was administered to detect limited reading ability. The SILS uses a five-point Likert-type scale (from 1, never, to 5, always). Scores greater than 2 are considered positive, indicating some difficulty with reading printed health-related material, and scores of 2 or less are considered negative.48 MAT is a previously validated Portuguese instrument that assesses self-reported medication adherence.49 The MAT consists of seven items that are assessed on a six-point Likert-type scale (from 1, always, to 6, never). The total score of the instrument ranges from 7 to 42, which is the result of the sum of all the responses.49 This tool was developed based on the instrument of Morisky Journal of the American Pharmacists Association
et al.,51 but three more items were added. In addition, the Portuguese study demonstrated that the use of a Likerttype scale granted better psychometric characteristics to the instrument than the dichotomic scale originally used by Morisky et al. Data analysis Descriptive statistical analysis was performed for instrument scores and sociodemographic data. Normality was assessed using the Kolmogorov–Smirnov test. A Pearson correlation test was used to explore the association between the NVS score and continuous or discrete variables, such as age, MAT score, and SILS score. Nonparametric tests (Mann–Whitney and Kruskal–Wallis) were used to investigate the association between the NVS score and categorical variables such as gender, education level, and SILS category (positive or negative for limited literacy). The tests were two tailed, and statistical significance was defined as P < 0.05. SPSS version 16 (SPSS, Chicago) was used for all analyses.
Results A total of 100 white older adults were enrolled in the study. The mean (±SD) age of the participants was 73.3 ± 7.83 years (range 58–89) and 71% were women. Age followed a normal distribution (P = 0.822 [Kolmogorov– Smirnov]), and no statistical difference in the age distribution of male and female participants was found (P = 0.699 [t test]). Participants’ level of education was as follows: 4.0% were unable to read or write, 71.0% completed elementary school, 15.0% completed high school, and 10.0% had higher education. The sample’s NVS score was 0.81 ± 0.10 (0.90 ± 0.25 for male participants and 0.77 ± 0.09 for female participants). The total NVS score did not follow a normal distribution (P < 0.001 [Kolmogorov–Smirnov]). The frequencies of the NVS total score revealed that 86% of participants scored between 0 and 1 and 95% scored in the three lowest possible scores, reflecting a floor effect distribution (Figure 1). The percentage of wrong answers among participants was around 90% for all questions other than question 5 (Table 1). A univariate analysis showed an inverse correlation between age and the NVS score (Pearson correlation coefficient –0.297; P = 0.003). However, no statistically significant difference was found between the NVS score and gender (P = 0.700 [Mann–Whitney]) or education level (P = 0.059 [Kruskal–Wallis]). The sample’s (n = 97) SILS score was 3.99 ± 1.2, with 88.7% participants classified as positive, indicating some difficulty with reading printed health-related material. No association between SILS categorical (positive or negative) and NVS score (P = 0.623 [Mann–Whitney]) was found. Likewise, no correlation between SILS score and NVS score (Pearson correlation coefficient –0.140; P = 0.167) was observed. j apha.org
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50% 45%
42%
44%
40%
Respondents
35% 30% 25% 20% 15% 9%
10%
3%
5%
1%
0%
1%
5
6
7
0% 1
2
3 4 NVS total score
Figure 1. NVS score distribution showing a floor effect in the health literacy assessment Abbreviation used: NVS, Newest Vital Sign.
Table 1. Percentage of wrong answers to each of the questions of the NVS NVS question 1. If you eat the entire container, how many calories will you eat? 2. If you are allowed to eat 60 g carbohydrates as a snack, how much ice cream could you have? 3. Your physician advises you to reduce the amount of saturated fat in your diet. You usually have 42 g saturated fat each day, which includes one serving of ice cream. If you stop eating ice cream, how many grams of saturated fat would you be consuming each day? 4. If you usually eat 2,500 calories in a day, what percentage of your daily value of calories will you be eating if you eat one serving? 5. Pretend that you are allergic to the following substances: penicillin, peanuts, latex gloves, and bee stings. Is it safe for you to eat this ice cream? 6. (Ask only if patient responds “no” to question 5) Why not?
% Wrong (n = 100) 94.0 89.0
98.0 94.0 49.0 95.0
Abbreviation used: NVS, Newest Vital Sign.
The sample’s (n = 97) MAT score was 36.2 ± 4.7 (range 17–42). Mean scores for each individual item are shown in Table 2. No correlation between NVS score and MAT was found (Pearson correlation coefficient –0.089; P = 0.379).
Discussion The current study revealed extremely low NVS scores (mean 0.81 [of 6 possible points]) for older adults, resulting in a remarkable floor effect that hindered the predictive power of the NVS score as a proxy for medication adherence in this population. Our results were not consistent with those reported in the original NVS 614 JAPhA | 5 3:6 | NOV/DEC 2013
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publication,9 which could be explained by the marked difference in the mean age of the populations (41.3 vs. 73.3 years).9 Nevertheless, a study enrolling older black patients aged similarly to the participants in our study did not show any floor effect.44 This difference between the performance of the NVS in the United States and Portugal may be a result of the widespread use of nutrition facts labels in the United States, causing consumers to be more familiar with them. In Portugal and other European countries, food labels have become widely used only recently. A study describing the cross-cultural adaptation of the NVS into Dutch discussed the need to change the NVS food label layout and content into a Journal of the American Pharmacists Association
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Table 2. Score of the MAT per item MAT question (n = 97) 1. Do you ever forget to take your medication? 2. Are you careless at times about taking your medication? 3. When you feel better, do you sometimes stop taking your medication? 4. Sometimes, if you feel worse when you take the medication, do you stop taking it? 5. Have you ever taken one or more pills for your illness after having felt worse? 6. Have you ever stopped taking your medication because you ran out of pills? 7. Have you ever stopped taking your medication for any other reason than the physician’s instruction?
Score Mean ± SD 4.8 ± 1.0 4.8 ± 1.3 5.0 ± 1.1 5.0 ± 1.4 5.5 ± 1.0 5.4 ± 0.8 5.6 ± 0.9
Percentile 25 4 4 4 5 6 5 6
Percentile 50 5 5 5 6 6 6 6
Percentile 75 6 6 6 6 6 6 6
Abbreviation used: MAT, Measure of Adherence to Therapy. A six-point Likert-type scale was used (from 1, always, to 6, never).
more European style but questioned the cross-cultural comparability that would result from the creation of a new instrument.50 In the original NVS publication, the authors note that the instrument “does not have the ceiling effect seen with the TOFHLA [Test of Functional Health Literacy Assessment] and, therefore the NVS provides better discrimination of skill levels among individuals in the upper part of the distribution of literacy skills.”9 By trying to avoid a ceiling effect, however, the NVS was created with such a degree of difficulty that it resulted in a floor effect distribution in our older population. The Dutch study reported a similar issue regarding the floor effect, but their sample included younger participants (mean age 59.7 years).50 The identified floor effect could be even more pronounced as a result of the underlying structure of the NVS, resulting in further overestimation of the health literacy assessment. In our study, the percentage of wrong answers among participants was nearly 90% for all questions, except question 5 (“Pretend that you are allergic to the following substances: penicillin, peanuts, latex gloves, and bee stings. Is it safe for you to eat this ice cream?”). A negative answer to this dichotomic question (correct answer) may not reflect full awareness by the respondents for two reasons: (1) this is the only question with a dichotomic answer in the NVS, and therefore participants have a 50% chance of scoring it correctly, and (2) for overcautious people, the way the question is presented may lead participants to unconsciously give the correct answer. To check these two potential biases and avoid misleading responses, we suggest that questions 5 and 6 ([“Ask only if patient responds ‘no’ to question 5] Why not?”) be scored as a composite question. This would shift the total possible score for the NVS from 6 to 5. Using the proposed criterion, only five individuals in our study would score this composite question, increasing the floor effect to 92% of participants scoring between 0 and 1 (instead of 86% previously). Two other studies also reported the fifth question to be the most correctly answered among parJournal of the American Pharmacists Association
ticipants, though at a higher percentage compared with our study (previous studies: 71.8% and 73.7%; current study: 51%).33,52 The participants in these two previous studies were younger than our respondents. Our results showed an inverse correlation between age and the NVS score, which also has been reported in a previous study.33 Conversely, the level of formal education of our population did not appear to be related to health literacy, which is not in keeping with previous literature.35,53 In our study, no association between the NVS and the SILS has been identified. However, these results should be interpreted carefully because they are likely affected by a potential lack of sensitivity of the NVS as a result of the identified floor effect. Medication adherence in older patients has been the focus of many previous reports.54–57 Rates of medication nonadherence are high among older adults, particularly among patients with chronic illnesses, in whom rates can approach 50%.58,59 Poor medication adherence has been associated with lower literacy.31,32 Participants in our study scored a mean of 36 points (maximum 42) on the MAT. This score suggests that the majority of participants in our sample tended to be adherent to drug therapy. However, our distribution involved participants with low adherence levels (range 17–42). No correlation between the NVS and MAT appeared, and again, this may result from the floor effect, which hampers the sensitive measurement of health literacy in older people. The current study has several potential implications for pharmacy practice. Our results suggest that pharmacists cannot rely on scores obtained from one of the most widely used health literacy instruments, the NVS, to screen older patients for low literacy. Although the NVS demonstrated high sensitivity in younger people,43 other studies also suggest that the NVS may not be suitable for older adults.44,60 Therefore, further instrument development and refinement among older adults is required. Alternative approaches in older people would be to assess “medication literacy”61,62 specifically instead of complete functional health literacy. Medication literacy was recently prej apha.org
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sented as aiming to measure the “ability of individuals to safely and appropriately access, understand, and act on information related to medication use.”62 Interventions on medication adherence are different among intentional and unintentional nonadherent patients, and these interventions should be designed to address specific patient characteristics. New instruments assessing medication literacy should be able to screen patients in a manner that results in more tailored patient counseling in the pharmacy setting and improved medication adherence.
7. Parker RM, Baker DW, Williams MV, Nurss JR. The test of functional health literacy in adults: a new instrument for measuring patients’ literacy skills. J Gen Intern Med. 1995;10(10):537–41. 8. Rudd R, Kirsch I, Yamamoto K. Literacy and health in America. Princeton, NJ: Educational Testing Service; 2004. 9. Weiss BD, Mays MZ, Martz W, et al. Quick assessment of literacy in primary care: the Newest Vital Sign. Ann Fam Med. 2005;3(6):514–22. 10. Barber MN, Staples M, Osborne RH, et al. Up to a quarter of the Australian population may have suboptimal health literacy depending upon the measurement tool: results from a population-based survey. Health Promot Int. 2009;24(3):252–61. 11. Brown L, Upchurch G, Frank SK. Low health literacy: what pharmacists can do to help. J Am Pharm Assoc. 2006;46(1):4–11.
Limitations The generalizability of the study findings beyond the current sample is unknown because the sample was not randomly selected. However, our aim was not to appraise health literacy in a representative sample of the Portuguese aged population but to assess the performance of the NVS and its association with adherence in this specific population. Another potential limitation to consider is participants’ embarrassment at answering a literacy questionnaire in an intervieweradministered fashion. Nevertheless, this was not an issue for respondents in a previous study.63
Conclusion The older adults in the current study performed weakly on the NVS, giving rise to a remarkable floor effect in the health literacy score distribution. This floor effect hinders the discriminatory power of the NVS and limits any correlation analysis with medication adherence. Therefore, these results indicate that the NVS is not useful in screening older adults for low health literacy and does not have utility as a proxy for medication adherence. Assessing medication literacy instead of complete functional health literacy may be more appropriate when attempting to associate health literacy with medication adherence and may help pharmacists provide more tailored patient counseling to older adults. References
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39. Heuberger RA, Caudell K. Polypharmacy and nutritional status in older adults: a cross-sectional study. Drugs Aging. 2011;28(4):315–23. 40. Hardin LR. Counseling patients with low health literacy. Am J Health Syst Pharm. 2005;62(4):364–5. 41. Sudore RL, Yaffe K, Satterfield S, et al. Limited literacy and mortality in the elderly: the Health, Aging, and Body Composition study. J Gen Intern Med. 2006;21(8):806–12. 42. Baker DW, Wolf MS, Feinglass J, et al. Health literacy and mortality among elderly persons. Arch Intern Med. 2007;167(14):1503–9. 43. Osborn CY, Weiss BD, Davis TC, et al. Measuring adult literacy in health care: performance of the Newest Vital Sign. Am J Health Behav. 2007;31(suppl 1):S36–46. 44. Patel PJ, Joel S, Rovena G, et al. Testing the utility of the Newest Vital Sign (NVS) health literacy assessment tool in older African-American patients. Patient Educ Couns. 2011;85(3):505–7. 45. Australian Bureau of Statistics. Health literacy, Australia: 2006. www. ausstats.abs.gov.au/ausstats/subscriber.nsf/0/73ED158C6B14BB5E CA2574720011AB83/$File/42330_2006.pdf. Accessed December 16, 2012
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57. Sirey JA, Greenfield A, Weinberger MI, Bruce ML. Medication beliefs and self-reported adherence among community-dwelling older adults. Clin Ther. 2013;35(2):153–60. 58. Chia LR, Schlenk EA, Dunbar-Jacob J. Effect of personal and cultural beliefs on medication adherence in the elderly. Drugs Aging. 2006;23(3):191–202. 59. Haynes RB, McDonald H, Garg AX, Montague P. Interventions for helping patients to follow prescriptions for medications. Cochrane Database Syst Rev. 2002;2:CD000011. 60. Kirk JK, Grzywacz JG, Arcury TA, et al. Performance of health literacy tests among older adults with diabetes. J Gen Intern Med. 2012;27(5):534–40. 61. King SR, McCaffrey DJ, Bouldin AS. Health literacy in the pharmacy setting: defining pharmacotherapy literacy. Pharm Pract (Granada). 2011;9(4):213–20. 62. Sauceda JA, Loya AM, Sias JJ, et al. Medication literacy in Spanish and English: psychometric evaluation of a new assessment tool. J Am Pharm Assoc. 2012;52(6):e231–40. 63. VanGeest JB, Welch VL, Weiner SJ. Patients’ perceptions of screening for health literacy: reactions to the Newest Vital Sign. J Health Commun. 2010;15(4):402–12.
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Newest Vital Sign as a proxy for medication adherence in older adults Teresa M. Salgado, Sara B. Ramos, Clésia Sobreira, Rita Canas, Inês Cunha, Shalom I. Benrimoj, and Fernando Fernandez-Llimos
Received December 28, 2012, and in revised form May 20, 2013. Accepted for publication June 18, 2013.
Abstract Objective: To assess the utility of the Newest Vital Sign (NVS) as a proxy for medication adherence in community-dwelling older adults. Design: Descriptive cross-sectional study. Setting: 12 adult day care centers in the Lisbon metropolitan area, Portugal, between March and May 2009. Participants: 100 white community-dwelling older adults. Intervention: Participants were administered the NVS, Single Item Literacy Screener (SILS), and self-reported Measure of Adherence to Therapy (MAT). Main outcome measures: Health literacy and medication adherence. Results: The mean (±SD) age of the respondents was 73.3 ± 7.8 years and 71% were women. The NVS score was 0.81 ± 0.10 (of 6 possible points), and 95% of the respondents scored in the three lowest possible scores, indicating a notable floor effect. Age was found to be inversely correlated with NVS score (P = 0.003). The MAT score was 36.2 ± 4.7 (range 17–42). No statistically significant association between the NVS and level of education (P = 0.059 [Kruskal–Wallis]), gender (P = 0.700 [Mann–Whitney]), SILS (P = 0.167), or MAT (P = 0.379) was identified. Conclusion: The utility of the NVS as a proxy for medication adherence in community-dwelling older adults is limited because of a floor effect that hinders its predictive power for medication adherence.
Teresa M. Salgado, MSc(Pharm), is a PhD candidate; Sara B. Ramos, MSc(Pharm) is a graduate student; Clésia Sobreira, MSc(Pharm) is a graduate student; Rita Canas, MSc(Pharm) is a graduate student; and Inês Cunha, MSc(Pharm) is a graduate student, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal. Shalom I. Benrimoj, PhD, is Head, Graduate School of Health, University of Technology, Sydney, Australia. Fernando FernandezLlimos, PhD, MBA, is Assistant Professor, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal. Correspondence: Fernando FernandezLlimos, PhD, MBA, Faculdade de Farmacia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. E-mail: [email protected] Disclosure: Ms. Salgado received a doctoral grant from the Portuguese Ministry of Education and Science. The other authors declare no conflicts of interest or financial interests in any product or service mentioned in this article, including grants, employment, gifts, stock holdings, or honoraria. Funding: Foundation for Science and Technology, Ministry of Education and Science, Portugal (doctoral grant no. SFRH/ BD/43999/2008).
Keywords: Adherence (medication), floor effect, health literacy, Newest Vital Sign, older patients.
Previous presentation: 41st European Society of Clinical Pharmacy Symposium on Clinical Pharmacy, October 28–31, 2012, Barcelona, Spain.
J Am Pharm Assoc. 2013;53:611–617. doi: 10.1331/JAPhA.2013.12249
Published online ahead of print at www. japha.org on October 4, 2013.
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H
ealth literacy was defined by the Institute of Medicine as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions.”1 Health literacy is a multifaceted concept2 that has evolved from the basic skills of reading and numeracy to critical thinking, problem solving, decision making, information seeking, and communication.3 Several instruments therefore have been developed to assess health literacy,4–9 and the Newest Vital Sign (NVS) is one of the most frequently used. However, none of these instruments fully grasps the concept of health literacy in terms of language, context, culture, communication, and technology.3 In addition, when comparing the performance of three of these instruments, they appear to measure different though related constructs.10 As medication information providers, pharmacists should be aware of patients’ health literacy level11,12 and tailor medication counseling to their needs.13 Inadequate health literacy can mean greater misunderstanding of drug information14,15 and lower medication management capacity.16,17 Low health literacy has been associated with poor health outcomes in conditions such as diabetes,18 chronic kidney disease,19 human immunodeficiency virus/acquired immunodeficiency syndrome,16 cancer,20 and asthma.21 Other studies revealed that patients with inadequate health literacy presented an increased risk of hospital admissions,22 less knowledge about their health
At a Glance Synopsis: This study assessed the utility of Newest Vital Sign (NVS)—one of the most frequently used health literacy assessment tools—as a proxy for medication adherence in community-dwelling older adults. The older adults in the current study performed poorly on the NVS, resulting in a floor effect in the health literacy score distribution that hinders the NVS’s predictive power for medication adherence. These results indicate that the NVS is not useful in screening older adults for low health literacy and does not have utility as a proxy for medication adherence. Analysis: Evidence has indicated that although the NVS has high sensitivity in younger people, it may not be suitable for older adults. Further development and refinement of health literacy instruments use among older adults is required. Assessing “medication literacy” specifically instead of complete functional health literacy may help pharmacists provide more tailored patient counseling to older people. New instruments that are designed to address specific patient characteristics should result in improved counseling and better medication adherence.
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problems,23,24 and higher health care costs.25,26 Conversely, some studies failed to demonstrate a significant association between health literacy and several clinical outcomes.27,28 Conflicting evidence exists for the relationship between health literacy and adherence, with some studies reporting no association29,30 and others showing a link between lower literacy and poorer adherence.31,32 Age and health literacy are inversely correlated.10,18,33–36 Assessing health literacy in older patients is extremely relevant because of the high prevalence of polypharmacy in this population, as shown by studies conducted in hospitals,37 nursing homes,38 and the community.39 Complex drug regimens and the technical communication frequently used by health professionals40 may cause older patients to be more prone to misunderstandings and subsequent drug use problems, which likely are exacerbated by inadequate health literacy. Further, limited literacy has been associated with increased mortality in older patients.41,42 The NVS has been described as a health literacy assessment tool with high sensitivity43 and short administration time.9 However, the NVS was originally validated in a relatively young population (mean age 41.3 years).9 The relationship between health literacy and medication adherence remains unclear, and few studies have evaluated the performance of health literacy instruments in older patients.44
Objective The aim of our study was to assess the utility of the NVS as a proxy for medication adherence in communitydwelling older adults.
Methods This cross-sectional study was conducted between March and May 2009. Ethics approval was granted by the Clinical Research Ethics Committee of the Faculty of Pharmacy, University of Lisbon (resolution no. 01/ CEECFFUL/2012). The study enrolled older adults attending 12 adult day care centers in Amadora, an urban municipality of the Lisbon metropolitan area in Portugal. Adult day care centers in Portugal are facilities at which older people get together, eat meals (e.g., breakfast, lunch, afternoon tea), and participate in leisure activities. Most of the people who attend these centers are fully functional and independent individuals who are responsible for managing their medications. This study was part of a broader investigation about medication follow-up. The recruitment was performed by approaching individuals attending adult day care centers, and those who agreed to participate were included in the study. No age restrictions were applied. To identify and exclude people with cognitive impairment, individuals were asked the date (month and year) and name of the adult day care center at which the study was taking place as a screening question. Considering a Journal of the American Pharmacists Association
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prevalence of 85% low literacy in older individuals,45,46 a CI of 95%, and the size of the Portuguese population older than 65 years (n = 1,874,209),47 the margin of error estimated for a sample size of 100 individuals was 7.0%. Before being invited to participate, potential respondents were informed about the objectives and methodology of the study and ensured that their anonymity would be preserved throughout the process. Individuals were free to withdraw at any time without further explanation, and no coercion to consent occurred. Individuals who agreed to participate gave their verbal consent and were subsequently administered three questionnaires: the NVS,9 Single Item Literacy Screener (SILS),48 and a previously validated Portuguese self-reported measure (Measure of Adherence to Therapy [MAT]).49 The questionnaires were administered by a member of the research team in the form of a structured interview. Sociodemographic data such as age, gender, and level of education also were collected. Study instruments The NVS is a six-question assessment based on an ice cream nutrition facts label that assesses numeracy skills, locate-the-information skills, and abstract reasoning skills. The final score is obtained through the number of correct and incorrect answers, with scores ranging from 0 to 6. Scores between 4 and 6 indicate sufficient health literate, 2 and 3 possible limited literacy, and 0 or 1 high likelihood (≥50%) of limited literacy.9 The original English version of the NVS was independently translated into Portuguese by members of the research team who were fluent in both languages. A consensual translated version was achieved following thorough discussion within the research team. Portuguese nutrition facts labels are similar to U.S. labels; therefore, we were able to maintain the structure of the original version of the instrument to enable international comparisons. This also has been reported in a previous European study.50 Assessments of the reliability and validity of the instrument were beyond the scope of this study. The SILS, which consists of a single question (“How often do you need to have someone help you when you read instructions, pamphlets, or other written material from your physician or pharmacy?”), was administered to detect limited reading ability. The SILS uses a five-point Likert-type scale (from 1, never, to 5, always). Scores greater than 2 are considered positive, indicating some difficulty with reading printed health-related material, and scores of 2 or less are considered negative.48 MAT is a previously validated Portuguese instrument that assesses self-reported medication adherence.49 The MAT consists of seven items that are assessed on a six-point Likert-type scale (from 1, always, to 6, never). The total score of the instrument ranges from 7 to 42, which is the result of the sum of all the responses.49 This tool was developed based on the instrument of Morisky Journal of the American Pharmacists Association
et al.,51 but three more items were added. In addition, the Portuguese study demonstrated that the use of a Likerttype scale granted better psychometric characteristics to the instrument than the dichotomic scale originally used by Morisky et al. Data analysis Descriptive statistical analysis was performed for instrument scores and sociodemographic data. Normality was assessed using the Kolmogorov–Smirnov test. A Pearson correlation test was used to explore the association between the NVS score and continuous or discrete variables, such as age, MAT score, and SILS score. Nonparametric tests (Mann–Whitney and Kruskal–Wallis) were used to investigate the association between the NVS score and categorical variables such as gender, education level, and SILS category (positive or negative for limited literacy). The tests were two tailed, and statistical significance was defined as P < 0.05. SPSS version 16 (SPSS, Chicago) was used for all analyses.
Results A total of 100 white older adults were enrolled in the study. The mean (±SD) age of the participants was 73.3 ± 7.83 years (range 58–89) and 71% were women. Age followed a normal distribution (P = 0.822 [Kolmogorov– Smirnov]), and no statistical difference in the age distribution of male and female participants was found (P = 0.699 [t test]). Participants’ level of education was as follows: 4.0% were unable to read or write, 71.0% completed elementary school, 15.0% completed high school, and 10.0% had higher education. The sample’s NVS score was 0.81 ± 0.10 (0.90 ± 0.25 for male participants and 0.77 ± 0.09 for female participants). The total NVS score did not follow a normal distribution (P < 0.001 [Kolmogorov–Smirnov]). The frequencies of the NVS total score revealed that 86% of participants scored between 0 and 1 and 95% scored in the three lowest possible scores, reflecting a floor effect distribution (Figure 1). The percentage of wrong answers among participants was around 90% for all questions other than question 5 (Table 1). A univariate analysis showed an inverse correlation between age and the NVS score (Pearson correlation coefficient –0.297; P = 0.003). However, no statistically significant difference was found between the NVS score and gender (P = 0.700 [Mann–Whitney]) or education level (P = 0.059 [Kruskal–Wallis]). The sample’s (n = 97) SILS score was 3.99 ± 1.2, with 88.7% participants classified as positive, indicating some difficulty with reading printed health-related material. No association between SILS categorical (positive or negative) and NVS score (P = 0.623 [Mann–Whitney]) was found. Likewise, no correlation between SILS score and NVS score (Pearson correlation coefficient –0.140; P = 0.167) was observed. j apha.org
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50% 45%
42%
44%
40%
Respondents
35% 30% 25% 20% 15% 9%
10%
3%
5%
1%
0%
1%
5
6
7
0% 1
2
3 4 NVS total score
Figure 1. NVS score distribution showing a floor effect in the health literacy assessment Abbreviation used: NVS, Newest Vital Sign.
Table 1. Percentage of wrong answers to each of the questions of the NVS NVS question 1. If you eat the entire container, how many calories will you eat? 2. If you are allowed to eat 60 g carbohydrates as a snack, how much ice cream could you have? 3. Your physician advises you to reduce the amount of saturated fat in your diet. You usually have 42 g saturated fat each day, which includes one serving of ice cream. If you stop eating ice cream, how many grams of saturated fat would you be consuming each day? 4. If you usually eat 2,500 calories in a day, what percentage of your daily value of calories will you be eating if you eat one serving? 5. Pretend that you are allergic to the following substances: penicillin, peanuts, latex gloves, and bee stings. Is it safe for you to eat this ice cream? 6. (Ask only if patient responds “no” to question 5) Why not?
% Wrong (n = 100) 94.0 89.0
98.0 94.0 49.0 95.0
Abbreviation used: NVS, Newest Vital Sign.
The sample’s (n = 97) MAT score was 36.2 ± 4.7 (range 17–42). Mean scores for each individual item are shown in Table 2. No correlation between NVS score and MAT was found (Pearson correlation coefficient –0.089; P = 0.379).
Discussion The current study revealed extremely low NVS scores (mean 0.81 [of 6 possible points]) for older adults, resulting in a remarkable floor effect that hindered the predictive power of the NVS score as a proxy for medication adherence in this population. Our results were not consistent with those reported in the original NVS 614 JAPhA | 5 3:6 | NOV/DEC 2013
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publication,9 which could be explained by the marked difference in the mean age of the populations (41.3 vs. 73.3 years).9 Nevertheless, a study enrolling older black patients aged similarly to the participants in our study did not show any floor effect.44 This difference between the performance of the NVS in the United States and Portugal may be a result of the widespread use of nutrition facts labels in the United States, causing consumers to be more familiar with them. In Portugal and other European countries, food labels have become widely used only recently. A study describing the cross-cultural adaptation of the NVS into Dutch discussed the need to change the NVS food label layout and content into a Journal of the American Pharmacists Association
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Table 2. Score of the MAT per item MAT question (n = 97) 1. Do you ever forget to take your medication? 2. Are you careless at times about taking your medication? 3. When you feel better, do you sometimes stop taking your medication? 4. Sometimes, if you feel worse when you take the medication, do you stop taking it? 5. Have you ever taken one or more pills for your illness after having felt worse? 6. Have you ever stopped taking your medication because you ran out of pills? 7. Have you ever stopped taking your medication for any other reason than the physician’s instruction?
Score Mean ± SD 4.8 ± 1.0 4.8 ± 1.3 5.0 ± 1.1 5.0 ± 1.4 5.5 ± 1.0 5.4 ± 0.8 5.6 ± 0.9
Percentile 25 4 4 4 5 6 5 6
Percentile 50 5 5 5 6 6 6 6
Percentile 75 6 6 6 6 6 6 6
Abbreviation used: MAT, Measure of Adherence to Therapy. A six-point Likert-type scale was used (from 1, always, to 6, never).
more European style but questioned the cross-cultural comparability that would result from the creation of a new instrument.50 In the original NVS publication, the authors note that the instrument “does not have the ceiling effect seen with the TOFHLA [Test of Functional Health Literacy Assessment] and, therefore the NVS provides better discrimination of skill levels among individuals in the upper part of the distribution of literacy skills.”9 By trying to avoid a ceiling effect, however, the NVS was created with such a degree of difficulty that it resulted in a floor effect distribution in our older population. The Dutch study reported a similar issue regarding the floor effect, but their sample included younger participants (mean age 59.7 years).50 The identified floor effect could be even more pronounced as a result of the underlying structure of the NVS, resulting in further overestimation of the health literacy assessment. In our study, the percentage of wrong answers among participants was nearly 90% for all questions, except question 5 (“Pretend that you are allergic to the following substances: penicillin, peanuts, latex gloves, and bee stings. Is it safe for you to eat this ice cream?”). A negative answer to this dichotomic question (correct answer) may not reflect full awareness by the respondents for two reasons: (1) this is the only question with a dichotomic answer in the NVS, and therefore participants have a 50% chance of scoring it correctly, and (2) for overcautious people, the way the question is presented may lead participants to unconsciously give the correct answer. To check these two potential biases and avoid misleading responses, we suggest that questions 5 and 6 ([“Ask only if patient responds ‘no’ to question 5] Why not?”) be scored as a composite question. This would shift the total possible score for the NVS from 6 to 5. Using the proposed criterion, only five individuals in our study would score this composite question, increasing the floor effect to 92% of participants scoring between 0 and 1 (instead of 86% previously). Two other studies also reported the fifth question to be the most correctly answered among parJournal of the American Pharmacists Association
ticipants, though at a higher percentage compared with our study (previous studies: 71.8% and 73.7%; current study: 51%).33,52 The participants in these two previous studies were younger than our respondents. Our results showed an inverse correlation between age and the NVS score, which also has been reported in a previous study.33 Conversely, the level of formal education of our population did not appear to be related to health literacy, which is not in keeping with previous literature.35,53 In our study, no association between the NVS and the SILS has been identified. However, these results should be interpreted carefully because they are likely affected by a potential lack of sensitivity of the NVS as a result of the identified floor effect. Medication adherence in older patients has been the focus of many previous reports.54–57 Rates of medication nonadherence are high among older adults, particularly among patients with chronic illnesses, in whom rates can approach 50%.58,59 Poor medication adherence has been associated with lower literacy.31,32 Participants in our study scored a mean of 36 points (maximum 42) on the MAT. This score suggests that the majority of participants in our sample tended to be adherent to drug therapy. However, our distribution involved participants with low adherence levels (range 17–42). No correlation between the NVS and MAT appeared, and again, this may result from the floor effect, which hampers the sensitive measurement of health literacy in older people. The current study has several potential implications for pharmacy practice. Our results suggest that pharmacists cannot rely on scores obtained from one of the most widely used health literacy instruments, the NVS, to screen older patients for low literacy. Although the NVS demonstrated high sensitivity in younger people,43 other studies also suggest that the NVS may not be suitable for older adults.44,60 Therefore, further instrument development and refinement among older adults is required. Alternative approaches in older people would be to assess “medication literacy”61,62 specifically instead of complete functional health literacy. Medication literacy was recently prej apha.org
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sented as aiming to measure the “ability of individuals to safely and appropriately access, understand, and act on information related to medication use.”62 Interventions on medication adherence are different among intentional and unintentional nonadherent patients, and these interventions should be designed to address specific patient characteristics. New instruments assessing medication literacy should be able to screen patients in a manner that results in more tailored patient counseling in the pharmacy setting and improved medication adherence.
7. Parker RM, Baker DW, Williams MV, Nurss JR. The test of functional health literacy in adults: a new instrument for measuring patients’ literacy skills. J Gen Intern Med. 1995;10(10):537–41. 8. Rudd R, Kirsch I, Yamamoto K. Literacy and health in America. Princeton, NJ: Educational Testing Service; 2004. 9. Weiss BD, Mays MZ, Martz W, et al. Quick assessment of literacy in primary care: the Newest Vital Sign. Ann Fam Med. 2005;3(6):514–22. 10. Barber MN, Staples M, Osborne RH, et al. Up to a quarter of the Australian population may have suboptimal health literacy depending upon the measurement tool: results from a population-based survey. Health Promot Int. 2009;24(3):252–61. 11. Brown L, Upchurch G, Frank SK. Low health literacy: what pharmacists can do to help. J Am Pharm Assoc. 2006;46(1):4–11.
Limitations The generalizability of the study findings beyond the current sample is unknown because the sample was not randomly selected. However, our aim was not to appraise health literacy in a representative sample of the Portuguese aged population but to assess the performance of the NVS and its association with adherence in this specific population. Another potential limitation to consider is participants’ embarrassment at answering a literacy questionnaire in an intervieweradministered fashion. Nevertheless, this was not an issue for respondents in a previous study.63
Conclusion The older adults in the current study performed weakly on the NVS, giving rise to a remarkable floor effect in the health literacy score distribution. This floor effect hinders the discriminatory power of the NVS and limits any correlation analysis with medication adherence. Therefore, these results indicate that the NVS is not useful in screening older adults for low health literacy and does not have utility as a proxy for medication adherence. Assessing medication literacy instead of complete functional health literacy may be more appropriate when attempting to associate health literacy with medication adherence and may help pharmacists provide more tailored patient counseling to older adults. References
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N OV/D EC 2013 | 53:6 |
JAPhA 617