1. ¹Department of Urology, University of Michigan Medical Center, Ann Arbor, MI, USA
2. ²Department of Health Policy and Administration, University of Illinois at Chicago School of Public Health, Chicago, IL, USA
3. ³Department of Urology, UCLA Schools of Medicine and Public Health, Los Angeles, CA, USA
4. ⁴Department of Medicine, Harvard Medical School, Boston, MA, USA
5. ⁵Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA, USA
6. ⁶National Institutes of Diabetes, Digestive and Kidney Diseases, Bethesda, MD, USA

Correspondence: Dr JQ Clemens, Department of Urology, University of Michigan Medical Center, 1500 East Medical Center Drive, Taubman Center 3875, Ann Arbor, MI 48109-5330, USA. E-mail: qclemens@umich.edu

Received 16 April 2009; Revised 4 May 2009; Accepted 4 May 2009; Published online 2 June 2009.

Abstract

The National Institutes of Health-chronic prostatitis symptom index (NIH-CPSI) is a commonly used 13-item questionnaire for the assessment of symptom severity in men with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). For each item, score ranges are 0–1 (6 items), 0–3 (2 items), 0–5 (3 items), 0–6 (1 item) and 0–10 (1 item). This scoring system is straightforward, but items with wider score ranges are de facto weighted more, which could adversely affect the performance characteristics of the questionnaire. We rescored the NIH-CPSI so that equal weights were assigned to each item, and compared the performance of the standard and rescored questionnaires using the original validation dataset. Both the original and revised versions of the scoring algorithm discriminated similarly among groups of men with CP (n=151), benign prostatic hyperplasia (n=149) and controls (n=134). The internal consistency of the questionnaire was slightly better with the revised scoring, but values with the standard scoring were sufficiently high (Cronbach's 0.80). We conclude that although the rescored NIH-CPSI provides better face validity than the standard scoring algorithm, it requires additional calculation efforts and yields only marginal improvements in performance.