Evaluation of a new quality of life questionnaire for patients with irritable bowel syndrome

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1 Aliment Pharmacol Ther 1997; 11: 547±552. Evaluation of a new quality of life questionnaire for patients with irritable bowel syndrome B. A. HAHN, L. J. KIRCHDOERFER, S. FULLERTON* & E. MAYER* Pharmacoeconomic Research, Glaxo Wellcome Inc., Research Triangle Park, North Carolina, USA; and *UCLA School of Medicine, Division of Digestive Diseases, Los Angeles, California, USA Accepted for publication 21 January 1997 SUMMARY Background: We describe the development and evaluation of a new disease-speci c instrument, the Irritable Bowel Syndrome Quality of Life Questionnaire (IBSQOL), which was designed for use in patients with irritable bowel syndrome. The IBSQOL measures 10 domains found to be relevant to patients with irritable bowel syndrome: emotional health, mental health, health belief, sleep, energy, physical functioning, diet, social role, physical role, and sexual relations. Methods: During its development and evaluation, the IBSQOL was administered to over 500 patients with irritable bowel syndromeðtwo groups of patients from tertiary care centres, three focus groups of 8±12 patients each, and 287 patients in a national irritable bowel syndrome support network. As a control, the IBSQOL was also administered to 37 patients who did not have irritable bowel syndrome but had other gastrointestinal disorders. Statistical analyses to test the reliability and validity of the IBSQOL were performed using Cronbach's a coef cient. Results: Responses from the focus groups indicated that the IBSQOL was easy to complete and did not require too much time to ll out (» 25 min). Statistical analyses of the nal 30-item version of the IBSQOL demonstrated that it had both adequate validity and reliability (a ³ 0.60). A comparison of mean IBSQOL scores of persons with and without irritable bowel syndrome (but with other gastrointestinal conditions) showed no difference between the two groups with irritable bowel syndrome; however, scores for both irritable bowel syndrome groups were considerably lower than for the non-irritable bowel syndrome group, suggesting better health-related quality of life in patients who do not have irritable bowel syndrome. This further demonstrated the validity of the IBSQOL in targeting questions and domains speci c to patients with irritable bowel syndrome. Conclusions: Evaluation of the IBSQOL included testing the questionnaire in a large number of patients, which resulted in a revised and well-constructed instrument that demonstrated both adequate validity and reliability. The IBSQOL is currently being used in largescale clinical trials to measure changes in quality of life in patients with irritable bowel syndrome following treatment intervention. INTRODUCTION There is growing recognition among physicians that to understand diseases more fully, there should be a Correspondence to: Dr B. A. Hahn, Pharmacoeconomic Research, Glaxo Wellcome Inc., Five Moore Drive, Research Triangle Park, NC 27709, USA. greater convergence of biomedical and psychosocial perspectives. Today traditional clinical indicators of the effects of illness and/or treatment can sometimes be supplemented with health-related quality of life measures. This is particularly important with respect to functional disease states, where there may be few biological markers. Irritable bowel syndrome, for example, is a functional disorder characterized by Ó 1997 Blackwell Science Ltd 547

2 548 B. A. HAHN et al. abdominal pain and/or altered stool patterns, and although it is non-life-threatening, the impairment it causes can have serious consequences for the patient. Studies have shown that irritable bowel syndrome can affect sleep, 1 employment, 2 sexual functioning, 3 leisure, travel, diet, and can cause depression and anxiety. 4, 5 Questionnaires have been used in clinical research, as well as by physicians, to describe symptoms of patients with irritable bowel syndrome and to differentiate irritable bowel syndrome from organic conditions such as in ammatory bowel disease. 6, 7 None of these questionnaires, however, have focused exclusively on measuring the impact of irritable bowel syndrome on dimensions of quality of life. In this paper, we describe the development and evaluation of a new diseasespeci c instrument, the Irritable Bowel Syndrome Quality of Life Questionnaire (IBSQOL). The criteria for evaluating a quality of life instrument have been studied in detail, and it is generally accepted that a questionnaire should be valid, reliable and responsive to change. 8 Results regarding two of these essential elements (reliability and validity) are provided. The third element, responsiveness to change, could not be tested in the present analyses but are being evaluated currently in clinical trials of treatments for irritable bowel syndrome. MATERIALS AND METHODS Development of the IBSQOL began with a review of the literature, an examination of questionnaires that contained items relevant to patients with irritable bowel syndrome, and discussions with clinicians concerning the symptomatology of irritable bowel syndrome and its effects on patients' lives. Many questions found to be pertinent to aspects of health-related quality of life in patients with irritable bowel syndrome were found in two previously validated questionnaires, the Heartburn Quality of Life 6 and the Bowel Symptom Checklist 7 questionnaires. Some questions were then modi ed to be more speci c to patients with irritable bowel syndrome. As in those two questionnaires, all questions in the IBSQOL were asked in the context of the previous 4 weeks, to allow patients to average their experience over this time period, rather than to respond for only the day that they answered the questionnaire or only with respect to their most severe period of illness. The set of questions were then reviewed by gastroenterologists to verify their relevance, resulting in a questionnaire consisting of 46 questions which formed 10 scales: emotional health, mental health, health belief, sleep, energy, physical functioning, diet, social role, physical role and sexual Figure 1. Sample questions and response options from the IBSQOL.

3 IBS QUALITY OF LIFE 549 relations. Sample questions showing various response options is shown in Figure 1. Scores were transformed to a scale of 0±100, with 100 representing the best possible quality of life score. The initial IBSQOL was administered to two geographically separate groups of patients diagnosed with irritable bowel syndrome at tertiary gastrointestinal clinics within major university hospitalsð126 patients from a site in California and 122 patients from a site in Tennessee. As a control, the questionnaire was also administered to 37 patients (from the Tennessee site) who did not have irritable bowel syndrome but had other gastrointestinal conditions. Based on these responses, the format of each question was evaluated, and the entire questionnaire was critically reviewed for question construction, wording and clarity by an expert on questionnaire design. The revised IBSQOL was then tested in three geographically diverse focus groups of 8±12 patients per group, all diagnosed with irritable bowel syndrome by gastroenterologists. Questionnaire validity Validity of a questionnaire indicates the degree to which it assesses what it purports to measure. Content validity (i.e. how well the IBSQOL measured the theoretical concepts that it was designed to measure) was assessed often during the design phase of the IBSQOL, using input from both the focus groups and gastroenterologists, and it was veri ed after the design phase by repeatedly checking with members of the sampled groups to ensure that the content of the questions were relevant and by reviewing all questionnaires for evidence that items were not misunderstood. Construct validity (i.e. how closely the IBSQOL was related to other known health measures) was tested by administering the revised questionnaire to 287 irritable bowel syndrome sufferers, members of a support group network in the US. The validity of the IBSQOL was also assessed using the known group technique, 9 whereby the scores from two groups of patients with irritable bowel syndrome (from the California and Tennessee sites) were compared with those of patients without irritable bowel syndrome but with other gastrointestinal conditions (from the Tennessee site). Statistical analyses of the validity of the IBSQOL were performed using a well-established method, Cronbach's a coef cient; 10 adequate validity was considered to be demonstrated when a ³ Questionnaire reliability The reliability of an instrument or a scale within that instrument is its ability to yield the same results on repeated trials under the same conditions. A common method of determining reliability uses test±retest measures. This technique, however, becomes problematic with health-related quality of life questionnaires, because patients are often able to recall their previous responses, which can then bias the results. 12 Instead we used an alternative method, whereby an internal reliability estimate could be calculated (again using Cronbach's a coef cient) at a single administration of the IBSQOL, by comparing half the questions within a scale with the other half. 11 Reliability was considered acceptable when a ³ RESULTS Patients in the two tertiary care groups and three focus groups included both men and women (age range: 18± 75 years) of different ethnic origins and races from a broad range of educational and income levels. Patients completed the questionnaire in» 25 min on average. In general, all groups con rmed that the IBSQOL was easy to complete, the concepts were clear and relevant to irritable bowel syndrome sufferers, and that no concept regarding the impact of irritable bowel syndrome on quality of life was omitted. Results from the initial 46-question IBSQOL administered to the two tertiary care groups revealed that all scales had adequate validity, with the exception of the health belief scale, which was then eliminated from the IBSQOL. Based on the suggestions from the focus groups and the results of the initial analysis, the number of scales in the IBSQOL was reduced from 10 to 9, and the number of items was reduced from 46 to 30 (Table 1). Results of the analysis of the revised IBSQOL administered to members of an irritable bowel syndrome support group are shown in Table 2. All scales were found to have similar variances, as re ected in their standard deviations from the mean. Scale-to-scale correlations revealed that the scales representing psychological well-being (e.g. emotional and mental health) were more closely correlated with each other (i.e. higher correlations) than with scales representing aspects of physical well-being (e.g. physical functioning or sexual relations), demonstrating that the instrument

4 550 B. A. HAHN et al. Table 1. Revised IBSQOL Scale Emotional Mental health Sleep Energy Physical functioning Diet Social role Role physical Sexual relations Items Angry about your irritable bowel syndrome Not as happy as usual Less satis ed with life Fed up or frustrated More nervous than usual Worried Downhearted and blue Upset Trouble falling asleep Irritable bowel syndrome cause you to wake up during night Irritable bowel syndrome cause you to wake up earlier than usual Feel emotionally worn out and tired Feel physically worn out and tired Restrict or reduce vigorous physical activities Restrict or reduce moderate physical activities Restrict or reduce mild physical activities Cause you not to eat when hungry Avoid certain foods/drinks Food seems unappealing Feel uncomfortable Avoid certain social activities Feel socially embarrassed yourself Feel irritable bowel syndrome got in the way of others' activities Affected ability to succeed Got less done Avoid certain work activities Affected how well I did my job Interfere with sexual activities Avoid sexual activities Less satis ed has good construct validity. The lowest reliability coef cient for any scale was 0.66 (diet scale), which was still considered acceptable; all the other scales had high reliability coef cients, ranging from 0.83±0.93. A comparison of mean IBSQOL scores of persons with and without irritable bowel syndrome (but with other gastrointestinal conditions) illustrate a difference between those with and without irritable bowel syndrome, but not between the two sample groups with irritable bowel syndrome (Figure 2). Scores for the group without irritable bowel syndrome were within the 90th percentile on all scales, while those for the two groups with irritable bowel syndrome were considerably lower, suggesting better health-related quality of life in patients who do not have irritable bowel syndrome. This Figure 2. Mean scores on the IBSQOL of two groups of patients with irritable bowel syndrome and a control group without irritable bowel syndrome. Table 2. Mean scores (s.d.), reliability coef cients (Cronbach's a coef cient), and scale-to-scale correlations of IBSQOL administered to a support group of persons suffering from irritable bowel syndrome (n = 227) Scale-to-scale correlations Scale Mean (s.d.) a coef cient (1) (2) (3) (4) (5) (6) (7) (8) Emotional (1) 42.0 (24.8) 0.89 Mental health (2) 66.8 (22.1) Sleep (3) 77.1 (23.2) Energy (4) 56.8 (28.4) Physical functioning (5) 76.0 (24.0) Diet (6) 61.3 (20.2) Social role (7) 42.6 (26.7) Physical role (8) 41.7 (27.3) Sexual relations (9) 64.9 (26.0)

5 IBS QUALITY OF LIFE 551 result further strengthens the validity of the IBSQOL in accurately targeting questions and domains speci c to patients with irritable bowel syndrome. DISCUSSION The direction of modern medicine (and subsequently health economics) has led towards a greater emphasis on collection of patient health information and outcome measures. One of the more useful tools created to accomplish this goal is the health-related quality of life questionnaire, which adds the dimension of the patient's own experience with illness and the rami cations of treatment beyond those of traditional clinical markers. One of our objectives in this paper was to provide a background to potential users of such questionnaires. Details of what comprises a `good' (i.e. reliable and valid) health-related quality of life questionnaire and how it is tested to ensure effectiveness may be useful to clinicians who are either already using questionnaires in their practice or are evaluating new instruments. Based on data collected from over 500 patients with irritable bowel syndrome, the IBSQOL was shown to have adequate validity and reliability. It measured the theoretical constructs it was intended to measure. That the IBSQOL was suf ciently disease-speci c (i.e. to irritable bowel syndrome) was clearly demonstrated in the differences in results observed between patients with irritable bowel syndrome and those without irritable bowel syndrome but with other gastrointestinal disorders. The patients without irritable bowel syndrome undoubtedly scored as highly as they did (90th percentile) on the IBSQOL because the questions were not perceived to be pertinent to their particular health conditions, despite the fact that their disorders might have produced similar symptoms, and not because they enjoyed a particularly high quality of life. A limitation of the IBSQOL is that it is a new instrument and has not yet been tested for its responsiveness to detect change in the disease over time or to assess a therapeutic interaction. Jaeschke & Guyatt 13 maintain that it is not uncommon to rst test the responsiveness of a new questionnaire in a clinical trial and suggest that ideally it should be tested in two studiesð rst in a study of disease variation in stable patients and secondly in a study of questionnaire score changes following a therapeutic intervention. Both studies using the IBSQOL are currently being planned, including testing in three international populations. In summary, the IBSQOL is a methodically developed disease-speci c quality of life questionnaire for use in patients with irritable bowel syndrome. Our analyses of the IBSQOL demonstrated adequate validity and reliabilityðrequired elements for a questionnaire. Although we have obtained these satisfactory results, as part of the continuous improvement process, the IBSQOL will be retested for its validity and reliability in various populations of patients with irritable bowel syndrome. Ongoing research will determine the ultimate usefulness of the IBSQOL in measuring changes in quality of life over time or following treatment. ACKNOWLEDGEMENTS This research was funded by Glaxo Wellcome Inc. We thank Rose Mills, MPH for review and assistance with this manuscript. Dr Hahn will be pleased to provide a copy of the modi ed IBSQOL to interested readers. REFERENCES 1 Sjodin I, Svedlund J. Psychological aspects of non-ulcer dyspepsia: a psychosomatic view focusing on a comparison between the irritable bowel syndrome and peptic ulcer disease. Scand J Gastroenterol 1985; 109: 51±8. 2 Whitehead WE, Winget C, Fedoravicius AS, Wolley S, Blackwell B. Learned illness behavior in patients with irritable bowel syndrome and peptic ulcer. Dig Dis Sci 1982; 27: 202±8. 3 Gutherie E, Creed FH, Whorwell PJ. Severe sexual dysfunction in women with irritable bowel syndrome: comparison with in ammatory bowel disease and duodenal ulceration. Br Med J 1987; 295: 557±8. 4 Dancy CP, Backhouse S. Towards a better understanding of patients with irritable bowel syndrome. J Adv Nursing 1993; 38: 1443±50. 5 Corney RH, Stanton R. Physical symptom severity, psychological and social dysfunction in a series of outpatients with irritable bowel syndrome. J Psychosom Res 1990; 5: 483±91. 6 Talley NF, Phillips SF, Melton LJ, Wiltgen C, Zinsmeister AR. A patient questionnaire to identify bowel disease. Ann Intern Med 1989; 111: 671±4. 7 Drossman DA. A questionnaire for functional bowel disorders. Ann Intern Med 1989; 8: 627±9. 8 Cox DR, Fitzpatrick R, Fletcher AE, Gore SM, Spiegelhalter DJ, Jones DR. Quality-of-life assessment: can we keep it simple? J R Stat Soc A 1992; 155(3): 353±93. 9 Hays RD, Anderson R, Revicki D. Psychometric considerations in evaluating health-related quality of life measures. Quality of Life Research 1993; 2: 441±9. 10 Cronbach LJ. Coef cient alpha and the internal structure of test. Psychometrika 1951; 16: 297±334.

6 552 B. A. HAHN et al. 11 Bootman JL, Townsend RJ, McGhan WF. Principles of Pharmacoeconomics. Cincinnati, Ohio: Harvey Whitney Books Company, Campbell DT, Stanley JC. Experimental and Quasi-Experimental Designs for Research. Boston: Houghton Mif in Company, Jaeschke R, Guyatt GH. How to develop and validate a new quality of life instrument. In: Spilker B, ed. Quality of Life Assessments in Clinical Trials. New York: Raven Press Ltd., 1990: 47±57.

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