The National Institutes of Health Chronic Prostatitis Symptom Index
Development and Validation of a New Outcome Measure
Published in: The Journal of Urology, v. 162, no. 2, Aug. 1999, p. 369-375
Posted on RAND.org on December 31, 1998
PURPOSE: Chronic abacterial prostatitis is a syndrome characterized by pelvic pain and voiding symptoms, which is poorly defined, poorly understood, poorly treated and bothersome. Research and clinical efforts to help men with this syndrome have been hampered by the absence of a widely accepted, reliable and valid instrument to measure symptoms and quality of life impact. The authors developed a psychometrically valid index of symptoms and quality of life impact for men with chronic prostatitis. MATERIALS AND METHODS: The authors conducted a structured literature review of previous work to provide a foundation for the new instrument. They then conducted a series of focus groups comprising chronic prostatitis patients at 4 centers in North America, in which they identified the most important symptoms and effects of the condition. The results were used to create an initial draft of 55 questions that were used for formal cognitive testing on chronic prostatitis patients at the same centers. After expert panel review formal validation testing of a revised 21-item draft was performed in a diverse group of chronic prostatitis patients and 2 control groups of benign prostatic hyperplasia patients and healthy men. Based on this validation study, the index was finalized. RESULTS: Analysis yielded an index of 9 items that address 3 different aspects of the chronic prostatitis experience. The primary component was pain, which we captured in 4 items focused on location, severity and frequency. Urinary function, another important component of symptoms, was captured in 2 items (1 irritative and 1 obstructive). Quality of life impact was captured with 3 items about the effect of symptoms on daily activities. The 9 items had high test-retest reliability (r = 0.83 to 0.93) and internal consistency (a = 0.86 to 0.91). All but the urinary items discriminated well between men with and without chronic prostatitis. CONCLUSIONS: The National Institutes of Health chronic prostatitis symptom index provides a valid outcome measure for men with chronic prostatitis. The index is psychometrically robust, easily self-administered and highly discriminative. It was formally developed and psychometrically validated, and may be useful in clinical practice as well as research protocols.