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A new condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence
British Journal of Obstetrics and Gynaecology October 2001, Vol. 108, pp. 1057–1067
A new condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence G. J. Bugg a,*, E. S. Kiff b, G. Hosker a Objective To design and validate a condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence. Design A psychometric study by postal survey. Setting South Manchester University Hospital, UK. Sample Two hundred and twenty women with known anal incontinence. Method The questionnaire was adapted from the King’s Health Questionnaire, a condition-specific healthrelated quality of life questionnaire for the assessment of women with urinary incontinence. The questionnaire was then tested for acceptability, reliability and validity by postal survey. Results The Manchester Health Questionnaire was found to be highly acceptable to women and showed excellent internal consistency, test–retest reliability, criterion and construct validity. Conclusion The questionnaire is both a valid and reliable instrument for the assessment of health-related quality of life among women with anal incontinence. It will be useful in many different clinical settings and be of practical use in the evaluation of women after childbirth. As the good response rates show it could be a successful part of a postal survey.
INTRODUCTION Anal incontinence is a condition that causes a great deal of distress and occurs mainly among women. People find it very difficult to talk about anal incontinence. A selfcompletion questionnaire is therefore a good way of asking women about their problem. This study validates a new condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence. Anal incontinence is a distressing and disabling condition causing significant morbidity predominantly in women. It affects the social, psychological, occupational, domestic, physical, and sexual lives of women of all ages. Vaginal delivery appears to be a major cause of anal incontinence in women 1,2. MacArthur et al. 3 found that only 14% of women with new faecal incontinence after childbirth had consulted a doctor. Even people consulting a hospital specialist about bowel symptoms are unlikely to voluntarily report incontinence as one of their symptoms 4. Marshall et al. 5 suggested that information of such an intimate nature is not easily obtained by using the common approach of direct question and answer but is better obtained by questionnaire. This theory is supported in a study by Khullar et al. 6that showed that 15% of a
St Mary’s Hospital, Central Manchester Hospitals NHS Trust, UK b Wythenshawe Hospital, South Manchester Universities NHS Trust, UK * Correspondence: Dr G. J. Bugg, 16 Old Towns Close, Tottington, Bury BL8 3LH, UK. q RCOG 2001 British Journal of Obstetrics and Gynaecology PII: S 0306-545 6(01)00245-5
women with urinary incontinence admitted to having faecal incontinence on direct questioning, whereas 26% admitted to it on self-completion of a questionnaire. A questionnaire should therefore be a useful tool for the assessment of anal incontinence in women. This article describes the development and psychometric evaluation of a health-related quality of life questionnaire, the Manchester Health Questionnaire, which is specific to the effects of anal incontinence (see Appendix 1). Coulter 7 suggests that the terms health status and health-related quality of life have come to mean a combination of subjectively assessed measures of health, including physical function, social function, emotional or mental state, burden of symptoms and sense of wellbeing. The questionnaire is designed to assess these domains and can be described as a health status or a health-related quality of life measure. There are two approaches to measuring health status or health-related quality of life. One can use generic measures that are designed to tap aspects of healthrelated effects of care across a broad population or one can use a condition-specific measure that addresses the specific elements that affect the lives of persons with a given condition. The former offers the advantage of allowing comparability across conditions, but it is not likely to be as sensitive to the effects of a given health problem 8. Although there were a number of generic health status questionnaires available for use at the time of starting this study, there were no condition-specific questionnaires for anal incontinence validated for a population of women from the United Kingdom. It is envisaged that the questionnaire will become a useful www.bjog-elsevier.com
1058 G. J. BUGG ET AL.
outcome measure in both clinical trials and clinical practice and for comparing different populations and samples with anal incontinence.
METHODS The Manchester Health Questionnaire is made up of items adapted from the King’s Health Questionnaire 9, a condition-specific health-related quality of life questionnaire for the assessment of urinary incontinence. Each item from the King’s Health Questionnaire was adapted to assess anal incontinence and the basic structure of the King’s Health Questionnaire was incorporated into the new measure. The health-related quality of life scale has domains assessing general perception of health, general impact of incontinence, role, physical function, social function, personal relationships, emotion, sleep/ energy and severity/coping measures, with a separate scale for the measurement of the severity of symptoms. Unlike the King’s Health Questionnaire, we used a fivepoint scoring system as opposed to a four-point system in an attempt to improve reliability. Scores in each domain range between zero and 100, a higher score indicating a greater impairment of health-related quality of life. Content validity consists of a judgement as to whether the questionnaire samples all the relevant or important content or domains. The questionnaire was initially reviewed for content validity by authors E.S.K and G.H. The questionnaire was then sent by post to female patients with known faecal incontinence. Initially 15 women were sent questionnaires and asked to fill them out and send back comments either on the completed questionnaire or on the comment sheet provided. Responses to the questionnaire were considered and amendments were made. The revised questionnaire was sent out again, and this process continued for three cycles until no further amendments could be made to the questionnaire. In addition, content validity was assessed by ten physiotherapy tutors. Finally 15 patients with known faecal incontinence were asked to read and answer the questionnaire. Each patient was then interviewed by a faecal incontinence nurse specialist and asked whether they thought the items in the questionnaire were representative of their problems and whether any questions should be added or removed. The questionnaire was pre-tested for ambiguity and ease of comprehension by 15 women without known faecal incontinence who had recently given birth. The questionnaire was also pre-tested by 20 midwives who routinely cared for women on the postnatal ward. Changes were made to the questionnaire based on the comments made at each stage. The final version was tested for test–retest reliability, internal consistency, criterion validity, convergent validity and acceptability. The questionnaire and a copy of the Short Form 36 10 questionnaire were sent to 236 women with faecal incon-
tinence. Female patients were selected consecutively from a database of outpatients who had previously been investigated for anal incontinence. The questionnaires were returned using a stamped self-addressed envelope. To ensure a good response we sent a pre-notification letter and up to two reminders were sent if there was no reply after two weeks. Responses to questionnaire items that are not evenly distributed over the range of alternatives can produce a situation where most responses are clustered at the bottom or top of the scale. These are referred to as floor and ceiling effects, respectively. Endorsement frequencies for all questions were examined to decide whether responses were well distributed across the response categories. The average maximum endorsement frequency (the mean of the most frequently endorsed category for each question) and the highest endorsement frequency were calculated. Reliability The reliability of the quality of life scale was assessed by the measurement of its internal consistency, and by measurement of its test–retest reliability. Internal consistency is measured by using Cronbach’s alpha statistic. Internal consistency refers to the degree of correlation between items forming a scale. It is expected that items forming a domain of the questionnaire should correlate moderately with each other but should contribute independently to the overall score in that domain. A perfect correlation of 1.0 suggests that questions are measuring an almost identical construct, resulting in item redundancy; whereas a poor correlation suggests that items may be testing a number of different traits. It has been suggested that an alpha value of $ 0.7 is acceptable 11. In order to measure test–retest reliability respondents were sent questionnaires between one to two weeks after responding to the initial questionnaire. The responses of the two completed questionnaires were then compared. In order to measure the extent of agreement within an individual between the two questionnaires the mean difference (average bias) was calculated for each domain, the 95% limits of agreement were also calculated. These are defined as the mean difference plus and minus two times the standard deviation of the difference. The 95% limits of agreement are the range of differences one might expect to encounter for an individual patient when the questionnaire is administered for a second time without warning. Validity The method used to assess content validity has already been described. Criterion validity was tested by measuring the correlation of the new measure with a previously validated measure of health status. As no suitable conditionspecific questionnaire exists, we performed validity testing against the UK version Short Form 36 questionnaire 10. Convergent validity assesses the extent to which an q RCOG 2001 Br J Obstet Gynaecol 108, pp. 1057–1067
QOL QUESTIONNAIRE FOR ANAL INCONTINENCE 1059
instrument measures the attributes it is intended to measure. Many different examples of convergent validity may be given for a measure such as the Manchester Health Questionnaire. In this study we chose one example by hypothesising that the more severe the symptoms of frank incontinence the higher the scores will be on the quality of life domains. The symptom scale has questions which relate to frank incontinence and ask how often a patient’s bowels leak when coughing and sneezing and how often a patient’s bowels leak when walking. These two questions were scored together to produce a score out of 100. A correlation was sought between the responses to these questions and the health status domain scores. On 191 questionnaires sent to patients an additional question was asked: “Did you find the question easy to understand and fill out”. Patient could respond either yes or no. Data analysis was performed using the SPSS statistical package, Version 9.0. The South Manchester research and ethics committee gave approval for this study. RESULTS Of the 236 initial mailings, 11 were returned by the post office because the patients were unknown at that address and five had died. We assumed the remaining 220 patients received questionnaires. One hundred and fifty-nine (72%) of the two hundred and twenty patients returned the questionnaires. One hundred and fifty-four sets of questionnaires were correctly completed and analysed. Only 92 respondents answered the personal function domain as respondents were asked to leave the items to this domain blank if they were not applicable. The mean age of respondents was 61 years (range 28–85). One hundred and twenty-two patients returned the retest questionnaire. One respondent answered no to the question “Did you find the questionnaire easy to understand and fill out”; seven respondents left the question blank and 113 respondents answered yes. Acceptability The average maximum endorsement frequency (calculated as the mean of the most frequently endorsed response category for each question) was 36%, with the highest maximum endorsement frequency being only 50.5% for question 19. The Cronbach’s alpha statistic exceeded the minimum requirements for reliability in all domains of the questionnaire (Table 1). A total of 121 respondents completed the questionnaire correctly on two occasions. The mean time between completion of the questionnaires was 20 days (range 7–50). The correlation of the two test results are shown in Table 1 and range from 0.81 to 0.92. The mean difference (average bias) between test one and test two and the 95% limit of agreement are presented in Table 2. q RCOG 2001 Br J Obstet Gynaecol 108, pp. 1057–1067
Table 1. Tests of reliability: internal consistency and test retest reliability. Domains General health Incontinence impact Role Physical function Social function Personal function Emotional problems Sleep/energy Severity measures a b
Internal consistency a
Test retest reliability b
N/A N/A 0.77 0.76 0.89 0.91 0.89 0.73 0.73
0.89 0.81 0.82 0.86 0.90 0.93 0.88 0.86 0.91
Internal consistency is expressed through the cronbach alpha statistic. Pearson correlation (P ,0.01 for all).
Validity No sample items were removed and no additions were made after content was reviewed by women with faecal incontinence and health professionals with experience in the field. During pre-testing it was found that women had difficulty understanding key words such as “faecal” and “stool”. These words had to be replaced with the term “bowel leakage” which was more easily understood. One hundred and fifty-four women who correctly filled out the Manchester Health Questionnaire also completed the Short Form 36 questionnaire. There were modest to strong correlation of the domains to both the Manchester Health Questionnaire and the Short Form 36 (Table 3). Correlation between the questions relating to frank incontinence and the health status domains are presented in Table 3. The correlations are modest to strong depending on the domain. Normative data scores for the healthrelated quality of life domains are presented in Table 4. DISCUSSION Respondents found the questionnaire easy to understand and fill out. The postal response rate for the questionnaire was 72%, and 98% of all respondents filled out the questionnaires in enough detail for them to be Table 2. Tests of reliability: the mean difference (average bias) for each domain between test one and test two with the corresponding 95% limit of agreement. The differences (test one–test two) have an approximate normal distribution as skewness was calculated and found to be between -1 to 1 in value. Domain
Mean difference (SD)
95% limit of agreement
General health Impact Role Physical function Social function Personal function Emotion Sleep/energy Severity measures
0 (11.2) 1.9 (15.9) 0.7 (15.7) 2.0 (15.6) -0.2 (12.8) 0 (11.94) 2.7 (13.2) -0.7 (14.2) 1.1 (11.5)
-22.3 to 22.3 -30.0 to 33.7 -30.7 to 32.1 -29.2 to 33.2 -25.7 to 25.3 -23.9 to 23.9 -23.7 to 29.1 -29.1 to 27.7 -22.0 to 24.2
1060 G. J. BUGG ET AL. Table 3. Tests of validity: criterion validity and convergent validity. Pearson correlation (P ,0.01 for all). N/A ¼ not applicable. The Short Form 36 score is high for good results where the faecal incontinence questionnaire score is high when results are poor. Domain General health Impact incontinence Role Physical function Social function Personal function Emotional function Energy Severity measures
Criterion validity -0.77 N/A -0.50 -0.50 -0.71 N/A -0.52 -0.35 N/A
between the two tests were small, ranging from zero to only 2.7 on a 100-point scale and the limits of agreement for each domain suggest the Manchester Health Questionnaire is a clinically effective tool of measurement.
Convergent validity 0.30 0.46 0.57 0.55 0.50 0.47 0.51 0.60 0.65
analysed, suggesting that women have no problems in self-completing the questionnaire in the privacy of their own homes. Examination of the endorsement frequencies for all questions showed that the floor and ceiling effects were avoided and responses were well distributed across response categories. Reliability The reliability of the questionnaire was excellent in terms of internal consistency. Test–retest reliability was also good. The time interval between the two tests was longer than used for the King’s Health Questionnaire, 20 days (7–50 days) compared with 9.2 days (2–16 days). A shorter test–retest interval may have influenced this measure. A reliability correlation coefficient $ 0.85 is considered adequate by some authors 12. The results for the domains role (0.82) and incontinence impact (0.81) are lower than this. However, other authors validating questionnaires have accepted lesser values. Brazier et al. 13 reported a test–retest reliability co efficient of 0.62 for the social function domain on the Short Form 36 and Kelleher et al. 9 reported a correlation coefficient of 0.80 on retest for the social function domain of the King’s Health Questionnaire. The mean differences (average bias) for each domain Table 4. Normative data: mean score for each domain, standard deviation and number of responses for each of the health related quality of life domains. Domains
Mean score (SD)
No. of responses
General health Incontinence impact Role Physical function Social function Personal function Emotional problems Sleep/energy Severity measures
36.1 (24) 56.9 (26.7) 40 (26.1) 44 (28.9) 32.3 (28.3) 27.9 (32.7) 47.6 (27.8) 31.5 (25.7) 57.7 (26.7)
151 150 153 153 153 93 147 149 147
Validity To establish content validity we asked patients and experts in the field to critically review the content of the scale; although this is a common procedure it is difficult, perhaps impossible, to prove formally that the items chosen are representative of all relevant items. The criterion validity of the Manchester Health Questionnaire was confirmed against the UK Short Form 36, the reliability and validity of which has been previously demonstrated. One example of convergent validity was also confirmed by the correlation between the items relating to faecal incontinence on the symptoms scale and the quality of life domains. Anal incontinence has been linked with urinary incontinence through a common mechanism of denervation and myogenic injury following childbirth 14,15. In addition, the symptomatology of the two forms of incontinence are similar. It is for these reasons we decided to adapt the King’s Health Questionnaire. The good results in terms of validity, reliability and acceptability support the decision. The symptom scale was administered with the quality of life scale and was pre-tested and judged for content validity but was not formally assessed for validity and reliability at any other stage. It is the intention of the authors that the symptom scale is always administered with the quality of life scale but that it is not scored. The symptom scale should act as a guide to help health professionals build up a picture of the patients’ condition, but the quality of life scale should be used to measure the severity of incontinence in terms of how it impacts on a woman’s health status. Normative data are presented in the paper for comparison purposes with other samples and populations with faecal incontinence (Table 4). It is also envisaged that the questionnaire will be a useful outcome measure in both clinical trials and clinical practice. However, first it has to be shown that the questionnaire can respond to change; this quality has not been demonstrated in this study but we expect it to be in further studies. A web site www.thethirddegree.org.uk has been set up to distribute the questionnaire, support users and co-ordinate its future development.
Acknowledgements This study was supported by a grant from the NHS R&D Directorate-North West. q RCOG 2001 Br J Obstet Gynaecol 108, pp. 1057–1067
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References 1. Swash M. Faecal incontinence. BMJ 1993;307:636–637. 2. Sultan AH. Anal incontinence after childbirth. Curr Opin Obstet Gynecol 1997;9:320–324. 3. MacArthur C, Bick DE, Keighly MR. Faecal incontinence after childbirth. Br J Obstet Gynaecol 1997;104:46–50. 4. Leigh RJ, Turnberg LA. Faecal incontinence: the unvoiced symptom. Lancet 1982;1:1349–1351. 5. Marshall K, Walsh DM, Baxter D. Faecal incontinence after childbirth [letter]. Br J Obstet Gynaecol 1997;104:870. 6. Khullar V, Damiano R, Toozs-Hobson P, Cardozo L. Prevalence of faecal incontinence among women with urinary incontinence. Br J Obstet Gynaecol 1998;105:1211–1213. 7. Coulter A. Measuring quality of life. In: Kinmouth AL, Jones R, editors. Critical Reading in General Practice, Oxford: Oxford University Press, 1993. 8. Avis NE, Smith KW. Conceptual and methodological issues in selecting and developing quality of life measures. In: Fitzpatrick R, editor. Quality of life in health care, Vol 5. Greenwich: JAI Press, 1994. 9. Kelleher CJ, Cardozo LD, Khullar V, Salvatore S. A new questionnaire
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10.
11. 12. 13.
14. 15.
to assess the quality of life of urinary incontinent women. Br J Obstet Gynaecol 1997;104:1374–1379. Health Services Research Unit, Department of Public Health and Primary Care. A Quality of Life Measurement in Health Care. A Review of Measures and Population Norms for the UK-SF-36. Oxford: University of Oxford, 1993. Nunnally JC. Psychometric Theory. New York: McGraw Hill Publishers, 1978. Weiner EA, Stewart BJ. Assessing individuals. Boston: Little Brown, 1984. Brazier JE, Harper R, Jones NMB, et al. Validating the SF-36 Health Survey questionnaire: new outcome measure for primary care. BMJ 1992;305:160–164. Snooks SJ, Setchell M, Swash M, Henry MM. Injury to the innervation of the pelvic floor musculature in childbirth. Lancet 1984;2:546–550. Thorpe AC, Roberts JP, Williams NS, Blandy JP, Badenoch DF. Pelvic floor physiology in women with faecal incontinence and urinary symptoms. Br J Surg 1995;82:173–176.
Accepted 29 May 2001
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APPENDIX 1. THE MANCHESTER HEALTH QUESTIONNAIRE
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A new condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence G. J. Bugg a,*, E. S. Kiff b, G. Hosker a Objective To design and validate a condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence. Design A psychometric study by postal survey. Setting South Manchester University Hospital, UK. Sample Two hundred and twenty women with known anal incontinence. Method The questionnaire was adapted from the King’s Health Questionnaire, a condition-specific healthrelated quality of life questionnaire for the assessment of women with urinary incontinence. The questionnaire was then tested for acceptability, reliability and validity by postal survey. Results The Manchester Health Questionnaire was found to be highly acceptable to women and showed excellent internal consistency, test–retest reliability, criterion and construct validity. Conclusion The questionnaire is both a valid and reliable instrument for the assessment of health-related quality of life among women with anal incontinence. It will be useful in many different clinical settings and be of practical use in the evaluation of women after childbirth. As the good response rates show it could be a successful part of a postal survey.
INTRODUCTION Anal incontinence is a condition that causes a great deal of distress and occurs mainly among women. People find it very difficult to talk about anal incontinence. A selfcompletion questionnaire is therefore a good way of asking women about their problem. This study validates a new condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence. Anal incontinence is a distressing and disabling condition causing significant morbidity predominantly in women. It affects the social, psychological, occupational, domestic, physical, and sexual lives of women of all ages. Vaginal delivery appears to be a major cause of anal incontinence in women 1,2. MacArthur et al. 3 found that only 14% of women with new faecal incontinence after childbirth had consulted a doctor. Even people consulting a hospital specialist about bowel symptoms are unlikely to voluntarily report incontinence as one of their symptoms 4. Marshall et al. 5 suggested that information of such an intimate nature is not easily obtained by using the common approach of direct question and answer but is better obtained by questionnaire. This theory is supported in a study by Khullar et al. 6that showed that 15% of a
St Mary’s Hospital, Central Manchester Hospitals NHS Trust, UK b Wythenshawe Hospital, South Manchester Universities NHS Trust, UK * Correspondence: Dr G. J. Bugg, 16 Old Towns Close, Tottington, Bury BL8 3LH, UK. q RCOG 2001 British Journal of Obstetrics and Gynaecology PII: S 0306-545 6(01)00245-5
women with urinary incontinence admitted to having faecal incontinence on direct questioning, whereas 26% admitted to it on self-completion of a questionnaire. A questionnaire should therefore be a useful tool for the assessment of anal incontinence in women. This article describes the development and psychometric evaluation of a health-related quality of life questionnaire, the Manchester Health Questionnaire, which is specific to the effects of anal incontinence (see Appendix 1). Coulter 7 suggests that the terms health status and health-related quality of life have come to mean a combination of subjectively assessed measures of health, including physical function, social function, emotional or mental state, burden of symptoms and sense of wellbeing. The questionnaire is designed to assess these domains and can be described as a health status or a health-related quality of life measure. There are two approaches to measuring health status or health-related quality of life. One can use generic measures that are designed to tap aspects of healthrelated effects of care across a broad population or one can use a condition-specific measure that addresses the specific elements that affect the lives of persons with a given condition. The former offers the advantage of allowing comparability across conditions, but it is not likely to be as sensitive to the effects of a given health problem 8. Although there were a number of generic health status questionnaires available for use at the time of starting this study, there were no condition-specific questionnaires for anal incontinence validated for a population of women from the United Kingdom. It is envisaged that the questionnaire will become a useful www.bjog-elsevier.com
1058 G. J. BUGG ET AL.
outcome measure in both clinical trials and clinical practice and for comparing different populations and samples with anal incontinence.
METHODS The Manchester Health Questionnaire is made up of items adapted from the King’s Health Questionnaire 9, a condition-specific health-related quality of life questionnaire for the assessment of urinary incontinence. Each item from the King’s Health Questionnaire was adapted to assess anal incontinence and the basic structure of the King’s Health Questionnaire was incorporated into the new measure. The health-related quality of life scale has domains assessing general perception of health, general impact of incontinence, role, physical function, social function, personal relationships, emotion, sleep/ energy and severity/coping measures, with a separate scale for the measurement of the severity of symptoms. Unlike the King’s Health Questionnaire, we used a fivepoint scoring system as opposed to a four-point system in an attempt to improve reliability. Scores in each domain range between zero and 100, a higher score indicating a greater impairment of health-related quality of life. Content validity consists of a judgement as to whether the questionnaire samples all the relevant or important content or domains. The questionnaire was initially reviewed for content validity by authors E.S.K and G.H. The questionnaire was then sent by post to female patients with known faecal incontinence. Initially 15 women were sent questionnaires and asked to fill them out and send back comments either on the completed questionnaire or on the comment sheet provided. Responses to the questionnaire were considered and amendments were made. The revised questionnaire was sent out again, and this process continued for three cycles until no further amendments could be made to the questionnaire. In addition, content validity was assessed by ten physiotherapy tutors. Finally 15 patients with known faecal incontinence were asked to read and answer the questionnaire. Each patient was then interviewed by a faecal incontinence nurse specialist and asked whether they thought the items in the questionnaire were representative of their problems and whether any questions should be added or removed. The questionnaire was pre-tested for ambiguity and ease of comprehension by 15 women without known faecal incontinence who had recently given birth. The questionnaire was also pre-tested by 20 midwives who routinely cared for women on the postnatal ward. Changes were made to the questionnaire based on the comments made at each stage. The final version was tested for test–retest reliability, internal consistency, criterion validity, convergent validity and acceptability. The questionnaire and a copy of the Short Form 36 10 questionnaire were sent to 236 women with faecal incon-
tinence. Female patients were selected consecutively from a database of outpatients who had previously been investigated for anal incontinence. The questionnaires were returned using a stamped self-addressed envelope. To ensure a good response we sent a pre-notification letter and up to two reminders were sent if there was no reply after two weeks. Responses to questionnaire items that are not evenly distributed over the range of alternatives can produce a situation where most responses are clustered at the bottom or top of the scale. These are referred to as floor and ceiling effects, respectively. Endorsement frequencies for all questions were examined to decide whether responses were well distributed across the response categories. The average maximum endorsement frequency (the mean of the most frequently endorsed category for each question) and the highest endorsement frequency were calculated. Reliability The reliability of the quality of life scale was assessed by the measurement of its internal consistency, and by measurement of its test–retest reliability. Internal consistency is measured by using Cronbach’s alpha statistic. Internal consistency refers to the degree of correlation between items forming a scale. It is expected that items forming a domain of the questionnaire should correlate moderately with each other but should contribute independently to the overall score in that domain. A perfect correlation of 1.0 suggests that questions are measuring an almost identical construct, resulting in item redundancy; whereas a poor correlation suggests that items may be testing a number of different traits. It has been suggested that an alpha value of $ 0.7 is acceptable 11. In order to measure test–retest reliability respondents were sent questionnaires between one to two weeks after responding to the initial questionnaire. The responses of the two completed questionnaires were then compared. In order to measure the extent of agreement within an individual between the two questionnaires the mean difference (average bias) was calculated for each domain, the 95% limits of agreement were also calculated. These are defined as the mean difference plus and minus two times the standard deviation of the difference. The 95% limits of agreement are the range of differences one might expect to encounter for an individual patient when the questionnaire is administered for a second time without warning. Validity The method used to assess content validity has already been described. Criterion validity was tested by measuring the correlation of the new measure with a previously validated measure of health status. As no suitable conditionspecific questionnaire exists, we performed validity testing against the UK version Short Form 36 questionnaire 10. Convergent validity assesses the extent to which an q RCOG 2001 Br J Obstet Gynaecol 108, pp. 1057–1067
QOL QUESTIONNAIRE FOR ANAL INCONTINENCE 1059
instrument measures the attributes it is intended to measure. Many different examples of convergent validity may be given for a measure such as the Manchester Health Questionnaire. In this study we chose one example by hypothesising that the more severe the symptoms of frank incontinence the higher the scores will be on the quality of life domains. The symptom scale has questions which relate to frank incontinence and ask how often a patient’s bowels leak when coughing and sneezing and how often a patient’s bowels leak when walking. These two questions were scored together to produce a score out of 100. A correlation was sought between the responses to these questions and the health status domain scores. On 191 questionnaires sent to patients an additional question was asked: “Did you find the question easy to understand and fill out”. Patient could respond either yes or no. Data analysis was performed using the SPSS statistical package, Version 9.0. The South Manchester research and ethics committee gave approval for this study. RESULTS Of the 236 initial mailings, 11 were returned by the post office because the patients were unknown at that address and five had died. We assumed the remaining 220 patients received questionnaires. One hundred and fifty-nine (72%) of the two hundred and twenty patients returned the questionnaires. One hundred and fifty-four sets of questionnaires were correctly completed and analysed. Only 92 respondents answered the personal function domain as respondents were asked to leave the items to this domain blank if they were not applicable. The mean age of respondents was 61 years (range 28–85). One hundred and twenty-two patients returned the retest questionnaire. One respondent answered no to the question “Did you find the questionnaire easy to understand and fill out”; seven respondents left the question blank and 113 respondents answered yes. Acceptability The average maximum endorsement frequency (calculated as the mean of the most frequently endorsed response category for each question) was 36%, with the highest maximum endorsement frequency being only 50.5% for question 19. The Cronbach’s alpha statistic exceeded the minimum requirements for reliability in all domains of the questionnaire (Table 1). A total of 121 respondents completed the questionnaire correctly on two occasions. The mean time between completion of the questionnaires was 20 days (range 7–50). The correlation of the two test results are shown in Table 1 and range from 0.81 to 0.92. The mean difference (average bias) between test one and test two and the 95% limit of agreement are presented in Table 2. q RCOG 2001 Br J Obstet Gynaecol 108, pp. 1057–1067
Table 1. Tests of reliability: internal consistency and test retest reliability. Domains General health Incontinence impact Role Physical function Social function Personal function Emotional problems Sleep/energy Severity measures a b
Internal consistency a
Test retest reliability b
N/A N/A 0.77 0.76 0.89 0.91 0.89 0.73 0.73
0.89 0.81 0.82 0.86 0.90 0.93 0.88 0.86 0.91
Internal consistency is expressed through the cronbach alpha statistic. Pearson correlation (P ,0.01 for all).
Validity No sample items were removed and no additions were made after content was reviewed by women with faecal incontinence and health professionals with experience in the field. During pre-testing it was found that women had difficulty understanding key words such as “faecal” and “stool”. These words had to be replaced with the term “bowel leakage” which was more easily understood. One hundred and fifty-four women who correctly filled out the Manchester Health Questionnaire also completed the Short Form 36 questionnaire. There were modest to strong correlation of the domains to both the Manchester Health Questionnaire and the Short Form 36 (Table 3). Correlation between the questions relating to frank incontinence and the health status domains are presented in Table 3. The correlations are modest to strong depending on the domain. Normative data scores for the healthrelated quality of life domains are presented in Table 4. DISCUSSION Respondents found the questionnaire easy to understand and fill out. The postal response rate for the questionnaire was 72%, and 98% of all respondents filled out the questionnaires in enough detail for them to be Table 2. Tests of reliability: the mean difference (average bias) for each domain between test one and test two with the corresponding 95% limit of agreement. The differences (test one–test two) have an approximate normal distribution as skewness was calculated and found to be between -1 to 1 in value. Domain
Mean difference (SD)
95% limit of agreement
General health Impact Role Physical function Social function Personal function Emotion Sleep/energy Severity measures
0 (11.2) 1.9 (15.9) 0.7 (15.7) 2.0 (15.6) -0.2 (12.8) 0 (11.94) 2.7 (13.2) -0.7 (14.2) 1.1 (11.5)
-22.3 to 22.3 -30.0 to 33.7 -30.7 to 32.1 -29.2 to 33.2 -25.7 to 25.3 -23.9 to 23.9 -23.7 to 29.1 -29.1 to 27.7 -22.0 to 24.2
1060 G. J. BUGG ET AL. Table 3. Tests of validity: criterion validity and convergent validity. Pearson correlation (P ,0.01 for all). N/A ¼ not applicable. The Short Form 36 score is high for good results where the faecal incontinence questionnaire score is high when results are poor. Domain General health Impact incontinence Role Physical function Social function Personal function Emotional function Energy Severity measures
Criterion validity -0.77 N/A -0.50 -0.50 -0.71 N/A -0.52 -0.35 N/A
between the two tests were small, ranging from zero to only 2.7 on a 100-point scale and the limits of agreement for each domain suggest the Manchester Health Questionnaire is a clinically effective tool of measurement.
Convergent validity 0.30 0.46 0.57 0.55 0.50 0.47 0.51 0.60 0.65
analysed, suggesting that women have no problems in self-completing the questionnaire in the privacy of their own homes. Examination of the endorsement frequencies for all questions showed that the floor and ceiling effects were avoided and responses were well distributed across response categories. Reliability The reliability of the questionnaire was excellent in terms of internal consistency. Test–retest reliability was also good. The time interval between the two tests was longer than used for the King’s Health Questionnaire, 20 days (7–50 days) compared with 9.2 days (2–16 days). A shorter test–retest interval may have influenced this measure. A reliability correlation coefficient $ 0.85 is considered adequate by some authors 12. The results for the domains role (0.82) and incontinence impact (0.81) are lower than this. However, other authors validating questionnaires have accepted lesser values. Brazier et al. 13 reported a test–retest reliability co efficient of 0.62 for the social function domain on the Short Form 36 and Kelleher et al. 9 reported a correlation coefficient of 0.80 on retest for the social function domain of the King’s Health Questionnaire. The mean differences (average bias) for each domain Table 4. Normative data: mean score for each domain, standard deviation and number of responses for each of the health related quality of life domains. Domains
Mean score (SD)
No. of responses
General health Incontinence impact Role Physical function Social function Personal function Emotional problems Sleep/energy Severity measures
36.1 (24) 56.9 (26.7) 40 (26.1) 44 (28.9) 32.3 (28.3) 27.9 (32.7) 47.6 (27.8) 31.5 (25.7) 57.7 (26.7)
151 150 153 153 153 93 147 149 147
Validity To establish content validity we asked patients and experts in the field to critically review the content of the scale; although this is a common procedure it is difficult, perhaps impossible, to prove formally that the items chosen are representative of all relevant items. The criterion validity of the Manchester Health Questionnaire was confirmed against the UK Short Form 36, the reliability and validity of which has been previously demonstrated. One example of convergent validity was also confirmed by the correlation between the items relating to faecal incontinence on the symptoms scale and the quality of life domains. Anal incontinence has been linked with urinary incontinence through a common mechanism of denervation and myogenic injury following childbirth 14,15. In addition, the symptomatology of the two forms of incontinence are similar. It is for these reasons we decided to adapt the King’s Health Questionnaire. The good results in terms of validity, reliability and acceptability support the decision. The symptom scale was administered with the quality of life scale and was pre-tested and judged for content validity but was not formally assessed for validity and reliability at any other stage. It is the intention of the authors that the symptom scale is always administered with the quality of life scale but that it is not scored. The symptom scale should act as a guide to help health professionals build up a picture of the patients’ condition, but the quality of life scale should be used to measure the severity of incontinence in terms of how it impacts on a woman’s health status. Normative data are presented in the paper for comparison purposes with other samples and populations with faecal incontinence (Table 4). It is also envisaged that the questionnaire will be a useful outcome measure in both clinical trials and clinical practice. However, first it has to be shown that the questionnaire can respond to change; this quality has not been demonstrated in this study but we expect it to be in further studies. A web site www.thethirddegree.org.uk has been set up to distribute the questionnaire, support users and co-ordinate its future development.
Acknowledgements This study was supported by a grant from the NHS R&D Directorate-North West. q RCOG 2001 Br J Obstet Gynaecol 108, pp. 1057–1067
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References 1. Swash M. Faecal incontinence. BMJ 1993;307:636–637. 2. Sultan AH. Anal incontinence after childbirth. Curr Opin Obstet Gynecol 1997;9:320–324. 3. MacArthur C, Bick DE, Keighly MR. Faecal incontinence after childbirth. Br J Obstet Gynaecol 1997;104:46–50. 4. Leigh RJ, Turnberg LA. Faecal incontinence: the unvoiced symptom. Lancet 1982;1:1349–1351. 5. Marshall K, Walsh DM, Baxter D. Faecal incontinence after childbirth [letter]. Br J Obstet Gynaecol 1997;104:870. 6. Khullar V, Damiano R, Toozs-Hobson P, Cardozo L. Prevalence of faecal incontinence among women with urinary incontinence. Br J Obstet Gynaecol 1998;105:1211–1213. 7. Coulter A. Measuring quality of life. In: Kinmouth AL, Jones R, editors. Critical Reading in General Practice, Oxford: Oxford University Press, 1993. 8. Avis NE, Smith KW. Conceptual and methodological issues in selecting and developing quality of life measures. In: Fitzpatrick R, editor. Quality of life in health care, Vol 5. Greenwich: JAI Press, 1994. 9. Kelleher CJ, Cardozo LD, Khullar V, Salvatore S. A new questionnaire
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to assess the quality of life of urinary incontinent women. Br J Obstet Gynaecol 1997;104:1374–1379. Health Services Research Unit, Department of Public Health and Primary Care. A Quality of Life Measurement in Health Care. A Review of Measures and Population Norms for the UK-SF-36. Oxford: University of Oxford, 1993. Nunnally JC. Psychometric Theory. New York: McGraw Hill Publishers, 1978. Weiner EA, Stewart BJ. Assessing individuals. Boston: Little Brown, 1984. Brazier JE, Harper R, Jones NMB, et al. Validating the SF-36 Health Survey questionnaire: new outcome measure for primary care. BMJ 1992;305:160–164. Snooks SJ, Setchell M, Swash M, Henry MM. Injury to the innervation of the pelvic floor musculature in childbirth. Lancet 1984;2:546–550. Thorpe AC, Roberts JP, Williams NS, Blandy JP, Badenoch DF. Pelvic floor physiology in women with faecal incontinence and urinary symptoms. Br J Surg 1995;82:173–176.
Accepted 29 May 2001
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APPENDIX 1. THE MANCHESTER HEALTH QUESTIONNAIRE
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