Free/total serum prostate-specific antigen ratio: how helpful is it in detecting prostate cancer?

To determine whether the use of free/total (f/t) serum prostate specific antigen (PSA) ratio would help reduce the number of prostate biopsies performed without compromising the detection of prostate cancer. in the setting of a transrectal ultrasonography (TRUS) clinic.

The study included 93 consecutive patients referred to the clinic for TRUS and biopsy. Serum samples were assessed for total PSA and free PSA, and the f/t PSA ratio calculated: 70 biopsies were taken. Patients over the age of 70 years with TRUS findings consistent with benign prostatic hyperplasia and with PSA levels < 10 ng/mL were not biopsied.

Tumour was detected in 23 patients; receiver operating characteristic curves showed no advantage for the f/t PSA ratio when compared with total PSA in detecting prostate cancer. If a f/t PSA ratio of < 0.15 had been used to determine the necessity for biopsy in the group with a total PSA of 4-10 ng/mL, then two-thirds of all tumours would have been undetected.

The f/t PSA ratio had no advantage over total PSA in improving specificity at a given sensitivity for detecting prostate cancer. Therefore, it cannot be recommended as a means of decreasing unnecessary biopsies in patients with a raised PSA level and/or an abnormal digital rectal examination. This applied particularly to the group of patients with a total PSA of 4-10 ng/mL.