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Tegaserod Treatment for IBS: A Model of Indirect Costs

Dean G. Smith, PhD; Victoria Barghout, MSPH; and Kristijan H. Kahler, SM

Irritable bowel syndrome (IBS) has been associated with substantial time lost from work (absenteeism) and reduced productivity at work (presenteeism), which are the indirect costs of illness. This article presents a productivity model demonstrating the indirect costs associated with IBS and the reduction in those costs for a cohort of female employees hypothetically treated with tegaserod, a new selective serotonin (5-hydroxytryptamine [5-HT]) type 4 (5-HT4) receptor agonist, which is approved by the US Food and Drug Administration for treating women with IBS-C. The model is based on economic and epidemiologic published literature and clinical trial results. In this model, tegaserod treatment resulted in $1882 in avoided lost productivity per treated female employee. Considering only the benefits of decreased work loss and the costs of medical therapy, the model predicts a benefit/cost ratio of 3.75 in the base case. From an employer's perspective, medical therapy for IBS with tegaserod is costeffective under a series of assumptions for the treatment of women with IBS with constipation.

(Am J Manag Care. 2005;11:S43-S50)

Estimates indicate that 75% of patients with irritable bowel syndrome (IBS) are between 25 and 64 years of age1; thus, most patients with IBS are of working age. IBS can have a negative impact on a patient's quality of life.2-4 In addition, it imposes a substantial economic burden on patients and the rest of society.1,5 The direct annual cost of IBS in the United States is estimated to be between $1.7 billion and $10 billion, excluding the cost of prescription and over-the-counter drugs.1,5 In addition to direct costs, IBS has been associated with substantial indirect costs resulting from time lost from work (absenteeism) and reduced productivity at work (presenteeism), costs that are borne largely by the employer. In fact, indirect costs—estimated to be as high as $20 billion1—may account for the largest proportion of the total IBS economic burden.5

Patients with IBS are typically categorized into subtypes based on bowel dysfunction. The categories are IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), and IBS that alternates between constipation and diarrhea (IBS-A),6 which is also known as mixed-bowel IBS. Until recently, IBS treatment options consisted of single agents (ie, antispasmodics, fiber, laxatives, antidiarrheals, antidepressants) for specific individual symptoms (ie, abdominal pain, constipation, diarrhea) or various combinations of therapies aimed at alleviating multiple symptoms in individual patients. However, 2 agents are now available in the United States that address multiple IBS symptoms.

Since its reintroduction in 2002 under restricted conditions for use (after having been withdrawn in 2000), alosetron, a serotonin (5-hydroxytryptamine [5-HT] type 3 (5-HT3) receptor antagonist, has been indicated for use in women with severe IBS-D that has not responded to conventional therapy. Tegaserod, a 5-HT4receptor agonist, has been indicated for use in women with IBS-C in the United States since 2002 and has recently been approved for men and women <65 years of age with chronic idiopathic constipation. In fact, tegaserod and alosetron were the only 2 agents to receive grade A recommendations from the American College of Gastroenterology Functional Gastrointestinal Disorder Task Force based on the high quality of published evidence supporting their global efficacy in IBS-C and IBS-D, respectively.6

This article presents an economic model of the indirect costs associated with IBS and the treatment of IBS with tegaserod. The purpose of the model is 2-fold: to demonstrate the impact that indirect costs associated with all IBS subtypes have on employers and to illustrate the potential costs and savings, in terms of indirect costs, associated with intervention for the treatment of patients with IBS-C using tegaserod as an example of cost-saving therapy. The workforce receiving the hypothetical treatment is that of Comerica Incorporated, a nationwide bank that offers personal, small business, and corporate banking services and that has major branches in Michigan, California, Texas, and Florida.

Methods

Data were obtained from a survey of the workforce at Comerica,7 from literature on the epidemiology and treatment of IBS, and from tegaserod clinical trial results. The model consists of several parameters that are specific for an employer and can be changed to customize the model results. Values based on the Comerica workforce are used as default values where possible in the model. The model can be used to analyze the indirect costs associated with IBS and the effect of treatment on these costs.

The Model

A representation of the workforce using demographics such as subpopulation sizes, sex, salaries, employment status (full-time vs part-time), illness (prevalence of IBS, incidence of IBS subtypes), and treatment (efficacy, costs) was constructed (Figure). Information on age and sex is based on data from the Comerica survey,7 and default values for salary are based on data from the Bureau of Labor Statistics.8 The proportions of male and female patients with IBS (default values of 7.7% [men] and 14.5% [women]) are based on data from the US Householder Survey.9 The proportion of women with IBS-C (default value of 28%) is based on the literature. 7 The proportion of patients with IBS who seek medical care (default value of 25%) was also based on the literature.10 A sample scenario was created in which women with IBS-C seeking medical attention were prescribed tegaserod. Sixty-seven percent of the women were assumed to have symptom control based on the highest efficacy value reported in the US tegaserod clinical trials,11 which, in turn, affects the number of courses of treatment, from 6 weeks to 54 weeks as described in the "Treatment" section.

Figure

Model Workforce

The workforce at Comerica has been examined for IBS prevalence and costs.7 The workforce is composed of 11 806 employees aged 18 to 64 years; 90% are employed full-time, and 10% are employed part-time.7 Although the age distribution of this workforce is typical, the percentage of women (77%) is greater than the norm (47%).8 Wages for persons in this workforce were distributed by age and sex, according to the average distribution reported by the US Department of Labor, Bureau of Labor Statistics, and averaged $19.82 per hour.8

Epidemiologic Data Sources

The baseline percentage of persons with IBS was based on data from the US Householder Survey,9 which surveyed a random sample of 8250 households in the National Family Opinion, Inc database. This survey was chosen because it provides data on IBS by age and sex.9

Percentages of patients with constipation (28%) and diarrhea (34%) as their primary altered bowel habit were based on the results of the Comerica survey.7 Results of this survey are similar to those from studies in the published literature that report that the 3 IBS subtypes occur with approximately equal frequency.12,13

The percentage of patients with IBS seeking medical care (25%) was based on evidence from the published literature.11 This rate represents a conservative estimate of healthcare-seeking behavior. Other studies in US populations have found healthcare-seeking rates as high as 45%.9,14

Productivity

The impact of symptoms and adverse effects from treatment on worker productivity has been documented for many well-known long-term conditions,15 including diabetes,16,17 asthma,18 and migraine,19 and for acute conditions, such as influenza.20 One commonly used measure of productivity loss is the Work Productivity and Activity Impairment (WPAI) questionnaire. The WPAI is a productivity-based questionnaire that was developed as a general health measure, and it has been modified and validated for specific health conditions, including IBS.21 It is designed to measure work impairment from absenteeism (time absent from work) and presenteeism (reduced productivity at work) and measure daily activity impairment, such as housework, shopping, childcare, and exercising, in the past 7 days.21 WPAI outcomes are expressed as impairment percentages, with higher numbers indicating greater impairment and less productivity.

Default values for absenteeism per employee with IBS (1.7%) and presenteeism per employee with IBS (21.1%) were based on results from the Comerica survey.7 Total lost productivity per employee with IBS (work productivity score [WPS]), which enumerates the reduced productivity attributed to IBS as a percentage of the potential total work productivity, was 21.1%, which is equivalent to working approximately 4 days of a 5-day work week) is also based on results of the Comerica survey.7 WPS is defined as [(Hours absent from work + percentage of reduced productivity at work × hours actually worked)/(hours missed because of ill health + hours worked)] × 100.

With a 5-day week for 50 weeks per year, a WPS of 21.1% translates into a total annual loss of 50 days because of IBS per employee. Because the model uses the average absenteeism and presenteeism values from all employees included in the survey to calculate the WPS rather than from individual employees (Comerica), an adjustment factor was applied to ensure that the model reflects the WPS for the Comerica workforce published in the literature.

Treatment

Medications are prescribed for most (89%) patients with IBS.22 This model enables an employer to calculate the costs and savings associated with a treatment option of their choice for a specific subpopulation of employees with IBS. The example used in this article is women with IBS-C who sought medical care and were treated with tegaserod, which is approved for this patient population.

The base value used in the model for the percentage of patients with satisfactory relief of IBS symptoms was 67%, which was based on the highest efficacy reported in the US tegaserod clinical trials.11 A range of values from 37% (the lowest efficacy value reported in the tegaserod clinical trials)23 to 67% are examined in the sensitivity analyses.

One assumption imposed to determine the treatment effect was that treatment with tegaserod permits 36% of lost productivity to be regained.24 A second assumption related to the extent of treatment (the annual number of IBS symptom episodes that patients experience and the annual number of prescriptions for tegaserod written per year). US Food and Drug Administration-approved prescribing instructions, consistent with supporting clinical trials, recommend a dosage of 6 mg twice daily for 4 to 6 weeks with an additional 4-to 6-week course as needed if the patient responds to therapy.23,25 Relief generally occurs within the first week of treatment for patients who respond, but symptoms may return after treatment has been stopped.11 Relief of the symptoms of IBS occurs in 67% of patients; hence, 33% of patients may end therapy after the first prescription. It is not known how many patients who respond to therapy require treatment beyond the refill amount. Trials have shown that tegaserod is safe in patients receiving a 12-month course of therapy.26

Outcome Measures

 
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