The usefulness of prostate specific antigen density as a screening method for prostatic carcinoma

Prostate specific antigen (PSA) has been used extensively for monitoring the progression of prostatic cancer since its discovery in 1979. Unfortunately the measurement of PSA in serum is not sufficiently specific for early detection of prostatic carcinoma (CaP) as it is secreted by normal as well as hyperplastic or cancerous prostatic tissue. As serum PSA is the reflection of the number of prostatic epithelial cells, a small cancerous prostate gland having increased number of cells per unit volume leaks more PSA in serum than a benign, large gland. Thus the concept of PSA density (PSAD) has been proposed (the quotient of serum PSA divided by the volume of prostate in cubic centimeter) as an indicator for prostatic malignancy. In the present study pre-operative PSAD values of 65 cases of prostatic diseases were calculated [54 cases of benign prostatic hyperplasia (BPH) and 11 cases of C3P]. Serum PSA was measured by enzyme linked immunosorbent assay (ELISA) method and the prostatic volume was measured by transrectal ultrasonography (TRUS). Although 8 cases of BPH (14.8%) had raised PSA level, abnormal PSAD (0.1 or above) was noted in only 3 cases. All cases having PSAD value above 0.2 had carcinoma. The PSAD value above 0.1 in cases of CaP was found to be significant (p<0.001). By using PSAD as screening test the sensitivity increased from 85.1% to 94.4% and positive predictive value increased from 55.5% to 75%, compared to the detection of carcinoma by measuring PSA alone. The present study concludes that PSAD is more useful for prediction of CaP and the need of prostatic biopsy for early detection.