Use of prostate-specific antigen (Psa) isoforms for the detection of prostate cancer in men with a PSA level of 3-10Ng/Ml: a Zimbabwean perspective

Total PSA (tPSA) has been used to diagnose prostate cancer although its performance as a screening test has several limitations including limited specificity. The main objective of the study was to determine the use of the PSA isoforms (free PSA, complex PSA and ratio of free/total PSA) in diagnosing prostate cancer among Zimbabwea men with tPSA levels between 3 and 10 ng/ml. A cross sectional study was done on 44 men attending a Urology Clinic at Harare Hospital (mean age = 70yrs). If tPSA was between 3 and 10ng/ml and the attending urologist requested a prostate biopsy a written consent was sought and the sample was analyzed for free and complexed PSA (cPSA). A follow up was made on the biopsy results. Statistical methods were then used to determine the use of the PSA isoforms (fPSA, cPSA and of f/tPSA ratio) in diagnosing prostate cancer. An increase in the fPSA significantly lowered the risk of developing prostate cancer (OR 0.01, p=0.003). However, the ratio of f/tPSA was more predictive of the occurrence of prostate cancer. Total PSA and cPSA were not significant (p=0.753 and 0.237 respectively). The ratio PSA test was highly predictive (AUC= 0.921, p=0.002) than free PSA (AUC=0.908, p=0.003). The study conforms to other reports postulating that f/tPSA ratio can aid in the diagnosis of prostate cancer in the 3–10 ng/ml range as compared to the use of tPSA alone with f/tPSA ratio being more predictive. The use of cPSA remains uncertain. Not withstanding resource limitations, there is a need for larger national cohort studies which may run concurrently with CaP awareness campaigns