Efficacy of PSA in the detection of carcinoma of the prostate in patients presenting with acute urinary retention.

Objectives: A temporary elevation in serum-prostate specific antigen (PSA) levels has been reported in association with acute urinary retention. In spite of this, it is not uncommon for clinicians to assay PSA at the time a patient presents with acute urinary retention. We sought to evaluate whether this practice can be justified. Patients and method: Fifty-four patients, aged between 55 and 89 years, who presented to a single institution with acute urinary retention were studied. A PSA assay was performed on admission and a record made of the prostatic size as assessed by digital rectal examination. All patients underwent a trial without catheter, those that failed to void underwent prostatic surgery whilst all others were followed up as outpatients. Results: Five patients were found to have prostatic carcinoma, three following transurethral resection of the prostate (TURP) and two following needle biopsy, performed because of persistent elevation of the PSA. A significant elevation in the PSA was associated with acute urinary retention, with only 15 (28%) patients having a PSA of 4.0 ng/ml or less. This elevation reduced the sensitivity of PSA in detecting carcinoma of the prostate; even with a cut-off of 20ng/ml, the positive predictive value of the test was only 21%. Conclusions: A PSA assay should not be performed at the time of presentation with acute urinary retention as it may lead to unnecessary investigations and anxiety for the patient. For those in whom a PSA assay is desirable a delay of 2 weeks should be allowed prior to sampling, as the half-life of PSA is known to be 2-3 days.