Background and objective
The characteristic symptom of chronic prostatitis (CP) is pain. Patients with CP often complain of lower urinary tract symptoms (LUTS); however, the voiding domain of the Chronic Prostatitis Symptom Index of the National Institutes of Health (NIH-CPSI) is not sufficient to evaluate LUTS. Therefore, we studied the relationship between the International Prostate Symptom Score (IPSS) and NIH-CPSI scores in men.
Materials and methods
We reviewed 870 men who visited our health care center for a general health check-up and completed IPSS and NIH-CPSI questionnaires between January 2014 and January 2019. An NIH-CPSI pain score ≥4 was defined as the presence of a prostatitis-like symptom (Group 1), and an NIHCPSI pain score less than <4 was defined as the absence of a prostatitis-like symptom (Group 2). The relationship between IPSS and NIH-CPSI sub-scores was investigated. The associations between the IPSS total score and NIH-CPSI sub-scores were assessed using multiple linear regression analysis.

Results
The mean IPSS total, voiding, storage, and quality-of-life (QOL) scores were higher in Group 1 than in Group 2. Group 1 had fewer subjects in the mild group and more in the moderate and severe groups than did Group 2. Among NIH-CPSI sub-scores, pain score showed the highest correlation between IPSS total (r=0.283), voiding (r=0.266), storage (r=0.237), and QOL score (r=0.263). In regression analysis, only the NIH-CPSI pain score was associated with the IPSS total score (B=0.962, p<0.001).
Conclusions
The NIH-CPSI pain score showed a weak but statistically significant correlation with the IPSS, but the NIH-CPSI voiding score did not. This finding suggests that patients with CP-like symptoms need to be surveyed using the IPSS questionnaire. It will also be helpful to screen for comorbidities of benign prostatic hyperplasia and CP.