Health-Related Quality of Life and Health Care Costs in Severe, Refractory Irritable Bowel Syndrome

The irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder that, in its severe form, incurs high health care costs through physician visits, investigations, treatments, and time off work. A recent report showed that patients attending a tertiary referral clinic have impaired health-related quality of life, similar to patients with gastroesophageal reflux disease and diabetes (1). The authors suggest that health-related quality of life should be an outcome measure in future trials of therapy for IBS. Other outcome measures for treatment trials of IBS include bowel symptoms (2), abdominal pain (3), and psychological status (2). It is health-related quality of life, however, that most closely accords with patients' own views of the severity of IBS. These views are determined by the limitations that IBS imposes on daily life (including number of days with pain, impaired productivity, and number of days spent in bed), rather than the severity of bowel symptoms (4). We do not fully understand the relationships among these aspects of medically unexplained symptoms. The biopsychosocial model proposes that the interaction of psychological factors with physiologic processes leads to the clinical presentation of IBS (5, 6). In this model, the final outcomes for the patient are health-related quality of life; for health planners, the outcomes are health care utilization and costs (5-7). It is unclear from existing literature whether health-related quality of life (measured by using a generic instrument) and health care costs are directly related to the severity of IBS symptoms (pain and bowel function) or are principally determined by other factors, such as psychological status or previous sexual abuse (8). One study of patients attending a tertiary clinic suggested that health-related quality of life was more closely associated with psychological status than bowel severity symptom (4). In contrast, two other studies suggested that both bowel symptom severity and psychological status contribute to certain aspects of health-related quality of life, as measured by the Medical Outcomes Survey 36-item short-form questionnaire (SF-36) (9, 10). In another tertiary clinic sample, severe sexual abuse was the clearest predictor of both impaired health-related quality of life and increased health care utilization (8, 11). No previous study has adequately measured bowel symptom severity, psychological symptoms, and history of sexual abuse to determine which of these are most closely associated with health-related quality of life, health care costs, and productivity costs. Psychological treatment is now recommended for patients with severe IBS that has not responded to conventional therapy (12). It is these patients who are most disabled by their illness and incur the greatest costs in terms of health care utilization and time off work (13). Thus, it is appropriate to include health-related quality of life and a measure of costs as outcome measures in such trials, rather than using only bowel symptom severity (12). If impairment of health-related quality of life and increased health care and other costs are largely attributable to the psychological disturbance that often accompanies IBS, psychological treatment may improve these outcomes even if bowel symptoms change little. Our study sought to determine whether bowel symptom severity or psychological symptoms are more closely associated with impaired health-related quality of life and high health care costs in patients with severe and chronic IBS [Figure 1]. The 257 participants attended a gastroenterology clinic, had severe IBS that had not responded to conventional therapy, and agreed to enter a trial of psychological treatment. We analyzed baseline data to test two hypotheses: 1) that both bowel symptom severity and psychological distress are independent predictors of health-related quality of life [including inability to work] and 2) that both bowel symptom severity and psychological distress are predictors of health care costs incurred over the previous 12 months. Figure 1. Postulated relationships between predictors and outcomes. Methods Patients Patients were recruited from seven secondary and tertiary gastroenterology clinics in the northern part of England. All potentially eligible patients were interviewed by the research clinician, and those who fulfilled the entry criteria were invited to participate. The entry criteria were 1) satisfaction of Rome criteria for IBS [14]; 2) symptom duration longer than 6 months; 3) failure to respond to usual medical treatment, including education, dietary advice, antispasmodic agents and laxatives, or antidiarrheal medication administered for a minimum of 3 months; 4) moderate to severe abdominal pain, defined as a score greater than 59 on a visual analogue scale [15]; 5) no contraindication to psychotherapy or a selective serotonin reuptake inhibitor [a contraindication might include the presence of psychotic disorders, severe personality disorder, active suicidal ideation, alcohol consumption >50 units per week, or current use of medication that could interact with a selective serotonin reuptake inhibitor]; 6) the ability to complete the study questionnaires; and 7) age 18 to 65 years. The ethics committee for each participating hospital approved the study protocol. All patients provided written informed consent to participate in the study, after it had been fully explained to them in detail by a clinical researcher. All assessments reported here were made before study entry. Predictors The assessment interview recorded demographic data and a detailed symptom and treatment history. This interview elicited any history of sexual abuse by using a questionnaire previously validated for IBS (8). Bowel Symptoms Patients completed a previously validated bowel symptom questionnaire, which includes a visual analogue scale of severity of current pain (15). They also completed a daily diary of the severity of 10 symptoms (nausea, abdominal pain, flatulence, bloating, hard stool, loose stool, urgency, straining, incomplete evacuation, and mucus) using a 7-point Likert scale. This diary was kept for 2 weeks before trial entry; the mean score over 14 days was used in the analysis. Psychological Symptoms Psychological symptoms were assessed by using the Symptom Checklist 90 Revised (SCL-90R) (16); the results are presented in the form of the global severity index and somatization subscale score. Depressive symptoms were assessed by using the Hamilton rating scale of depression (17). Outcome Measures Health-Related Quality of Life The SF-36 was used to measure health-related quality of life. This instrument covers aspects of physical, psychological, and social functioning (18). It has been shown to discriminate among different degrees of severity of IBS and is suitable for clinical trials (10, 19). Data are first presented as scores on eight conventional scales and then as the physical component summary (PCS) score; the mean (SD) for the general population is 50 10 (20). Low scores indicate poor health status. A low PCS score indicates the way in which the disorder limits self-care and daily activities, severe pain, and poor general health. For example, the score improves with recovery from congestive heart failure but not with recovery from depressive illness (20, 21). Costs Direct health care costs for 1 year before trial entry were derived by using activity data and by applying an appropriate unit cost to each recorded contact or episode of care. Costs were initially calculated in U.K. pounds and then recalculated in U.S. dollars. All patients were under a single-payer scheme, the United Kingdom National Health Service. Hospital costs included inpatient days, outpatient and day-patient attendance, and visits to accident and emergency departments. Nonhospital costs included all primary care contacts (general practitioner surgery and home visits, nurse practitioner, and practice-based counselors), domiciliary care services (National Health Service and local authority), and day rehabilitation centers. Use of alternative therapies (such as reflexology) and prescription medications was recorded, and their cost was included as part of direct health care costs (22). Unit costs were obtained wherever possible from local service providers or national data sets (23, 24). Direct nonhealth care costs incurred for 1 year before the assessment, including travel costs and additional patient expenditure, were recorded at the assessment. These included nonprescription medication, additional household expenditure, child care expenditure, and expenditures for housework or personal care. Loss of productivity costs incurred because of time off from work in the previous year were measured by applying the patient's wage rate to the number of days lost because the patient was ill or had attended medical visits. If patients were unemployed as a result of illness and were receiving sickness benefits, this was also recorded but not included in the main cost analysis. Statistical Analysis Continuous data are presented as the mean (SD) and were compared by using analysis of variance. For categorical variables, chi-square tests were used. Stepwise multiple regression was used to identify the independent variables associated with the SF-36 PCS score, days of restricted activity, and costs. The variables entered into these regression analyses were demographic characteristics (age, sex, years of education, and history of abuse), measures of IBS severity (visual analogue scale of abdominal pain today, mean diary score, number of days of pain during last month, and number of years of bowel problems), psychological assessments (Hamilton depression score, SCL-90R global severity index, and somatization scores). Patients unemployed as a result of ill health were compared with the remaining patients, and a forward stepwise logistic regression was performed to