Objectives: To assess the direct medical costs, medication, and procedure use associated with interstitial cystitis (IC) in women in the Kaiser Permanente Northwest (KPNW) managed care population. Methods: The KPNW electronic medical record was used to identify women diagnosed with IC (n = 239). Each of these patients was matched with three controls according to age and duration in the health plan. Health plan cost accounting data were used to determine the inpatient, outpatient, and pharmacy costs for 1998 to 2003. An analysis of the prescription medication use and cystoscopic and urodynamic procedures commonly associated with IC was also performed. To evaluate for co-morbidities, an automated risk-adjustment model linked to 28 chronic medical conditions was applied to the administrative data sets from both groups. Results: The mean duration from the date of IC diagnosis to the end of the study period was 36.6 months (range 1.4 to 60). The mean yearly costs were 2.4-fold greater for the patients than for the controls ($7100 versus $2994), and the median yearly costs were 3.8-fold greater ($5000 versus $1304). These cost differences were predominantly due to outpatient and pharmacy expenses. Medication and procedure use were significantly greater for the patients than for the controls. These findings were consistent across risk-adjustment model categories, which suggest that the observed cost differences are IC specific. Conclusions: The direct per-person costs of IC are high, with average yearly costs approximately $4000 greater than for the age-matched controls. This cost differential is an underestimate, because the costs preceding the diagnosis, the use of alternative therapies, indirect costs, and the costs of those with IC that is not diagnosed were not included.
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