PSAD is determined by dividing the PSA number by the prostate volume (its size as measured by transrectal ultrasound). Johns Hopkins doctors recommend this measurement “to help differentiate between cancer and BPH in men with moderately high PSA levels (4 to 10 ng/mL) and normal DRE results.”

The theory is that cancer causes a greater elevation in PSA per prostate volume than BPH. If so, PSA density should be higher in men with cancer. To find PSA density, doctors divide the PSA results by prostate volume (as estimated by transrectal ultrasound). This method is imperfect, according to the Hopkins experts; but, they add, “studies showing that PSA density levels over 0.15 indicate a high risk of cancer have led doctors to use PSA density tests for men with PSA levels between 4 and 10 ng/mL.”

Some recent studies have shown however that PSA density is not a very useful measurement.
A Spanish teams a couple of years ago said: “We conclude that PSAD and PSADTZ are not excessively useful for adequately discriminating between patients with prostate cancer and those with non-malignant disease, particularly when digital rectal examination is normal.” (Garcia Sisamon F, et al, 2003). Now a study in Kuwait, published this month, has found similarly:

Utility of volume adjusted prostate specific antigen density in the diagnosis of prostate cancer in arab men.

Sheikh M, Al-Saeed O, Kehinde EO, Sinan T, Anim JT, Ali Y.

Department of Radiology, Faculty of Medicine, Kuwait University, P.O. Box 24923, 13110, Safat, Kuwait

Background: This study was undertaken to assess the utility of prostate specific antigen (PSA) and PSA density (PSAD) in discriminating between benign and malignant prostate disease in the Kuwaiti Arab population.

Methods: A total of 100 consecutive patients suspected of having prostate cancer because of serum PSA > 4 ng/ml, or detection of a prostatic nodule on rectal examination were further investigated by determination of PSAD, TRUS of prostate, sexant prostatic biopsy and histological analysis to establish the correct diagnosis. Other diagnostic measures included the determination of the area under the receiver operating characteristic (ROC) curve, sensitivity and specificity.

Results: Of the 100 prostate biopsies that were performed, 33 cases were confirmed to be prostate cancer and 67 were described as benign lesions comprising benign prostatic hyperplasia (BPH) with or without prostatitis. The age range for patients with prostate cancer was 42-90 years, and 52-90 years for those without prostate cancer.

The mean prostate volume was 58.82 cc (range 9-177 cc) and 62.60 cc (range 15-140 cc), the mean PSA value was 36.65 ng/ml (range 5.8-200 ng/ml) and 16.49 ng/ml (range 1.4-46.0 ng/ml), while the mean PSAD was 0.92 (range 0.046-5.714) and 0.452 (range 0.034-2.294) for patients with prostate cancer and patients without prostate cancer respectively.

Patients with PSA less than 4 ng/ml (3 cases) all had benign prostate lesions, and 7 cases with PSA more than 50 ng/ml all had prostate cancer and were excluded because values above 50 ng/ml have close to 100% specificity for prostate cancer. Further analysis was done on the remaining 90 cases which were patients with a PSA between 4 and 50 ng/ml.

The discriminating power of serum PSA for detecting prostate cancer as estimated by the area under ROC was 0.686 while that for PSAD was 0.732. The maximum likelihood for a positive PSA was at a PSAD cut-off point of 0.32. For the PSA cut-off point of 10 ng/ml, the sensitivity was 80%, and specificity was 42.2%. For the PSAD cut-off point of 0.32, the sensitivity was 58% and the specificity 76.6%.

Conclusions: Determination of PSAD is not a useful adjunct to serum PSA values in the range of 10-50 ng/ ml in our population. PSAD value less than 0.32 with PSA less than 10 ng/ml strongly suggests benign disease.