SANDRA BERRY, MA

Santa Monica, CA—A comprehensive, national effort to produce an estimate of the prevalence of interstitial cystitis/painful bladder syndrome (IC/PBS) in adult U.S. women has arrived at preliminary figures consistent with those of smaller estimates of this difficult-to-pin-down condition.

The RAND Interstitial Cystitis Epidemiology (RICE) study, led by researchers from RAND Corp., Santa Monica, CA, found that approximately 2.7% to 6.5% of American women age 18 years and over meet RICE symptom criteria for IC/PBS. In whole numbers, that translates to between 3.4 and 7.9 million women who have symptoms consistent with this debilitating condition.

"We don't say that we have measured specifically the prevalence of interstitial cystitis/painful bladder," principal investigator Sandra Berry, MA, senior behavioral scientist at RAND, told Urology Times. "What we've been able to measure is the prevalence of a constellation of symptoms that are consistent with those conditions in the population of U.S. women."

The study began with an expert panel process to determine which symptoms were likely indicators of a diagnosis of IC/PBS and which symptoms differentiated IC/PBS from conditions with overlapping symptoms. The researchers then conducted telephone interviews with a sample of nearly 600 women who had been diagnosed by physicians with IC/PBS and/or overactive bladder, endometriosis, or vulvodynia to pinpoint questions that best identified women diagnosed with IC/PBS and differentiated them from women diagnosed with the other conditions.

A second phase of the study used a two-stage population screening approach. First, an omnibus phone interview was conducted in nearly 100,000 households to screen for the presence of women with bladder symptoms. A second stage of screening was conducted to identify women who met IC/PBS criteria and did not meet standard exclusion criteria.

Weighted data were used to calculate prevalence estimates for both a high-sensitivity and a high-specificity definition of IC/PBS.

High-sensitivity definition criteria were:

• pain, pressure, or discomfort in the pelvic area
• and daytime urinary frequency (10-plus times per day) or urgency due to pain, pressure, or discomfort—not fear of wetting.

High-specificity definition criteria were:

• pain, pressure, or discomfort in the pelvic area
• and daytime urinary frequency (10-plus times) or urgency due to pain, pressure, or discomfort (not fear of wetting)
• and symptoms that did not resolve after treatment with antibiotics
• and no treatment with leuprolide (Lupron) for endometriosis.

Based on the more inclusive high-sensitivity definition, approximately 6.5% of adult women have symptoms consistent with IC/PBS. Based on the high-specificity definition, about 2.7% of women have symptoms consistent with the condition.

"Regardless of which definition you apply, there are quite a lot of women in the community who have these symptoms that bother them, and the symptoms have been present for a period of time," said study co-author J. Quentin Clemens, MD, MS, associate professor of urology at the University of Michigan, Ann Arbor. "As a field in general, we may want to start paying a little more attention to trying to identify better these individuals and sort out how we can better help them, because it does appear to be a pretty significant public health issue."

Study data were presented at the AUA annual meeting in Chicago, where session co-chair J. Curtis Nickel, MD, professor of urology at Queens University, Kingston, Ontario, called the data "absolutely fantastic."

"I perceive that this will be the citation that we'll all be using when we look for a definitive prevalence of IC-like symptoms," Dr. Nickel said.

The study was continuing at this writing, and the data are preliminary. Final data will be submitted for publication.