Validity and Responsiveness of the National Institutes of Health Chronic Prostatitis Symptom Index

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Abstract
The National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI) was validated in a sample of men with longstanding prostatitis but it has not been validated in primary care samples or assessed for responsiveness to change. We assessed its reliability, validity and responsiveness to change in a sample of men with pelvic pain visits to health maintenance organization primary care and urology clinics. A total of 261 men with recent primary care or urology clinic visits for pelvic pain and no evidence of specific disease completed the NIH-CPSI and validated generic pain and health-related quality of life measures (Graded Chronic Pain Scale, Short-Form 36 and Short-Form 12 scales) in a telephone interview approximately 1 month after the visit, of whom 230 (88%) completed the measures again 3 months later. Validity was demonstrated for the NIH-CPSI pain and quality of life scales through their moderate correlations with other validated measures of these constructs. The NIH-CPSI total scale but not the subscales showed high internal consistency. The pain, quality of life and total scores were moderately responsive to change (effect size −0.57 to −0.60), but the urinary symptoms scale was less responsive (effect size −0.18). The NIH-CPSI total score appears to be a valid, reliable, responsive measure of prostatitis symptoms in primary and secondary care patients. The findings support the use of the total score as an outcome measure. It may be useful to supplement it with valid, reliable measures of pain intensity and activity interference.