NBME Form 13 Practice Test

Chronic bacterial prostatitis is diagnosed by showing that bacteria come from the prostate, which is best demonstrated by comparing urine cultures collected before and after prostatic massage. In the Meares-Stamey approach, the amount of bacteria in the urine before prostatic massage is low, but after massage it rises markedly—typically about tenfold or more. This large post-massage increase indicates the prostate is releasing bacteria into the urinary tract, confirming infection of prostatic tissue.

Other options don’t pinpoint prostatitis specifically. Serum PSA is a marker more relevant to cancer or other prostatic conditions, not a bacterial infection. A urine dipstick for leukocytes can indicate urinary inflammation but doesn’t reveal the prostatitis source. Ultrasound measuring prostate size helps assess structural issues like enlargement or masses but not infection of the gland. So the pre- and post-massage urine cultures with a significant increase are the best way to confirm chronic bacterial prostatitis.