The RAND Interstitial Cystitis Epidemiology Study (RICE) is an observational study that sought to develop a case definition for Bladder Pain Syndrome (BPS)/Interstitial Cystitis (IC) with known sensitivity and specificity and to estimate the prevalence of the condition, which at the time had never been done using a large-population model. BPS/IC, which is clinically diagnosed based on patient-reported symptoms, is a poorly understood condition that can cause significant disability.

An expert panel developed a case definitions of BPS/IC based on a review of medical literature. This definition was tested on 599 adult women diagnosed with BPS/IC or other conditions characterized by pelvic symptoms. Testing revealed that no single epidemiological definition demonstrated both high sensitivity and high specificity, so two definitions were developed: one of high sensitivity/low specificity and one of low sensitivity/high specificity. Using these two definitions, researchers then screened 96,995 US households to identify women who had bladder symptoms. Those with symptoms underwent a secondary, more intensive screening and were asked to provide more information regarding symptoms, medical history, medical treatments, impact on daily life, physical and mental health, and demographic information. Multivariate modeling was used to construct population and non-response weights. Weighted data was used to calculate prevalence estimates for both definitions and estimate the number of women affected.

The RICE study sought to develop a symptom-based case definition of BPS/IC for epidemiological research and use that definition to estimate the prevalence of IC in adult women.

Outcome measures included the development and validation of two case definitions to identify BPS/IC.

During large population screening, households were screened for adult women of 18 years or older who had current symptoms of BPS/IC and/or had previously been diagnosed with BPS/IC.

Based on the high sensitivity definition, 6.53% of women met symptom criteria. Based on the high specificity definition, 2.70% of women met the criteria. These percentages translated into 3.3 to 7.9 million United States women 18 years old or older with bladder pain syndrome/interstitial cystitis symptoms. The RICE study suggests that the prevalence of BPS/IC in women is higher than previous estimates.