Evaluating serum free PSA percentage in prostatectomy cases

Prostate cancer is one of the most common cancers in men and the fourth common cancer in Iran. Prostate specific antigen (PSA) is the most useful tumor indicator for diagnosing premature Prostate cancer. The specificity and sensitivity of this test increases significantly when we measure the amount of serum free PSA and calculate the percentage.This is a descriptive – analytical study that was done on 125 patients who were under prostatectomy. The patients were divided into 4 groups of <60, 60-69, 70-79 and 80 years old or above In terms of their total PSA (tPSA), the patients were divided to 3 groups of normal (0-3.9ng/ml), borderline (4-9.9 ng/ml) and increased (10-19.9 ng/ml and 20 or more). As for their percentage of free PSA (fPSA%), they were divided to 3 groups of less than 18%, 18% -25% and more than 25%. Considering the biopsy results, they made 2 groups of BPH and cancer. After that, the tPSA and fPSA% were compared for diagnosing prostate cancer using statistical particularity and sensitivity tests.The finding of the study indicate that by increasing the cut-off values of fPSA% up to 25%, the probability of being afflicted by cancer decreased, especially within the limit of tPSA of 4-9.9ng/ml by which 18.2% of cases were diagnosed as BPH, but there was no indication of cancer (P=0.0001). According to the results of our study, the tPSA within 4-9.9ng/ml was a good indicator for recognizing 7.1% cases of cancer. The rate of its sensitivity and specificity in diagnosing cancer was 20% and 77.39%, respectively. However, in combination with fPSA% cut-off 18-25%, the rate of sensitivity increased to 53.57%; and that of specificity to 86.6% (0.001). In our study, fPSA%, in combination with tPSA, was able to increase the specificity and sensitivity of the tPSA test. Especially with fPSA% cut-off 18-25% in tPSA within the borderline limit of 4-9.9 ng/ml, which was the purpose of our study, it was able to diagnose cancer to a maximum degree in addition to increasing the sensitivity and specificity. Therefore, we suggest that fPSA% be used as an aid test to tPSA, especially when the tPSA falls within low or borderline ranges which may be the an indication of cancer in early stages. So, it would increase the diagnostic accuracy of prostate cancer and decrease the costs involved.