The National Institutes of Health chronic prostatitis symptom index: Development and validation of a new outcome measure

Purpose: Chronic abacterial prostatitis is a syndrome characterized by pelv ic pain and voiding symptoms, which is poorly defined, poorly understood, p oorly treated and bothersome. Research and clinical efforts to help men wit h this syndrome have been hampered by the absence of a widely accepted, rel iable and valid instrument to measure symptoms and quality of life impact. We developed a psychometrically valid index of symptoms and quality of life impact for men with chronic prostatitis. Materials and Methods: We conducted a structured literature review of previ ous work to provide a foundation for the new instrument. We then conducted a series of focus groups comprising chronic prostatitis patients at 4 cente rs in North America, in which we 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 pro statitis patients at the same centers. After expert panel review formal val idation testing of a revised 21-item draft was performed in a diverse group of chronic prostatitis patients and 2 control groups of benign prostatic h yperplasia patients and healthy men. Based on this validation study, the in dex was finalized. Results: Analysis yielded an index of 9 items that address 3 different aspe cts of the chronic prostatitis experience. The primary component was pain, which we captured in 4 items focused on location, severity and frequency. U rinary function, another important component of symptoms, was captured in 2 items (1 irritative and 1 obstructive). Quality of life impact was capture d with 3 items about the effect of symptoms on daily activities. The 9 item s had high test-retest reliability (r = 0.83 to 0.93) and internal consiste ncy (alpha = 0.86 to 0.91). All but the urinary items discriminated well be tween 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. Th e index is psychometrically robust, easily self-administered and highly dis criminative. It was formally developed and psychometrically validated, and may be useful in clinical practice as well as research protocols.