Background
Serum prostate specific antigen (PSA) test is used globally for prostate cancer screening, however its low specificity causes diagnostic dilemma and a number of patients have to undergo unnecessary biopsies. Our earlier study reported that PSP94, another prostatic protein, when used in conjunction with PSA leads to an improvement in its diagnostic potential. We aim to assess the utility of PSP94/PSA ratio (PP Index) in minimizing referrals for prostate biopsies in patients having lower urinary tract symptoms (LUTS) and with PSA levels between 4–20 ng/ml.
Methods
Patients having LUTS were recruited for this prospective study (n = 833). Estimation of PSP94 was carried out using an in house developed ELISA and PSA tests were carried out at a centralized lab. Samples showing PSA levels in the range of 4–20 ng/ml were considered further for the study (n = 226). Out of these, the biopsy results of 139 participants were available. Receiver operating characteristic (ROC) curve analysis was performed to determine the area under the curve (AUC), sensitivity and specificity of PP Index. To establish the diagnostic potential of PP Index as compared to PSA and PSP94, we performed decision curve analyses (DCA).
Results
On the basis of PSA alone, 100% of the participants in the PSA range of 4–20 ng/ml were recommended for biopsy whereas if PP Index with a cut off value of ≤ 5.26 had been used, ~ 50% of prostate biopsies could have been avoided. At a cut off of ≤ 5.26, the PP Index had a sensitivity of 100% and specificity of 53.49%. The DCA revealed that at a threshold probability of 5%, the PP index can help to avoid 49.64% of the biopsies.
Conclusions
PSP94 as an adjunct marker along with PSA (PP Index) has the ability to differentiate between prostate cancer and BPH at PSA levels between 4–20 ng/ml and thus can help clinicians in better decision making.