Correlation between 2 interstitial cystitis symptom instruments

Abstract

Purpose: Two statistically validated interstitial cystitis (IC) symptom instruments have been used in clinical research. In this study we report what is to our knowledge the first direct comparison of the University of Wisconsin Symptom Instrument (UWI) with the O'Leary-Sant instruments, that is the IC Symptom Index (ICSI) and IC Problem Index (ICPI).

Materials and methods: A convenience sampling of 107 patients with IC evaluated at the urology clinic at our institution from March through August 2000 were asked to complete ICSI, ICPI and UWI. The scores were analyzed and graphed.

Results: Mean ICSI, ICPI and UWI scores +/- SD were 12.6 +/- 4.3, 10.5 +/- 3.8 and 25.5 +/- 10.8, respectively. UWI and ICSI scores correlated at r = 0.80 (p <0.01) and ICSI/ICPI scores correlated at r = 0.83 (p <0.01). ICSI and ICPI contain 4 symptom-problem pairs. There are relevant differences in the correlation of symptom severity (ICSI question) and its associated problem (ICPI question). The symptom of urgency correlated best with the associated problem (r = 0.84), followed by nocturia (r = 0.82), pain (r = 0.70) and frequency (r = 0.68).

Conclusions: The ICSI and UWI symptom instruments correlate strongly in a large population of patients with IC. The data presented will aid in interpreting the literature. A relatively poor correlation between pain symptom-problem pairs in the O'Leary-Sant instruments is probably an artifact of wording. The word pressure appears in ICPI but not in ICSI. We suggest using parallel wording of the pain symptom-problem pair containing the identical phrase, burning, pain, discomfort or pressure, to improve the ICSI/ICPI correlation and more accurately reflect the clinical condition.