Utility of PSA isoform-[-2]proPSA (p2PSA) and prostate health index in the diagnosis of prostate cancer: A study in Indian population

Background: Measurement of serum total Prostate Specific Antigen (tPSA) for diagnosis of Prostate Cancer (PC) has some limitations since PSA is organ-specific and not disease-specific. Studies across the globe have shown that measuring the isoform of PSA: [-2]-Pro-PSA(p2PSA) and calculating the Prostate Health Index (PHI) increase the specificity, however, very few studies have been done in the Indian population. Aim and Objectives: To evaluate tPSA, p2PSA and PHI as diagnostic markers of PC. Material and Methods: The pre-biopsy blood samples of 152 subjects were analysed in Beckman-Coulter Access-2 for tPSA, freePSA (fPSA) and p2PSA and %fPSA, %p2PSA and PHI ([p2PSA/fPSA] x root tPSA) were calculated. Validity indicators were calculated along with Area under the receiver operating Curve (AUC). Results: Of 152 subjects, 85 subjects (55.9 %) had PC, and others showed No evidence of Malignancy (NEM). The median tPSA (ng/ml), p2PSA (pg/ml), %p2PSA,IPSA (pg/ml) and PHI values were significantly (p<0.001) higher in the PC group than NEM group (148 ng/ml vs. 9.11 ng/ml; 612.3 pg/ml vs. 14.52 pg/ml; 4.98% vs. 1.59 %; 15.7 pg/ml vs. 1.26 pg/ml and 440.19 vs. 32.14 respectively). PSA at cut off value of 10 ng/ml had 91.8% sensitivity, 58.2% specificity, Negative Predictive Value (NPV) 84.8% and Positive Predictive Value (PPV) 73.6%. At a cut-off of 100 pg/ml p2PSA had 81.7% sensitivity, 97.0% specificity, 80.2% NPV, 97.2 % PPV and AUC was 0.930 [95% Confidence Interval(CI): 0.88-0.97]. PHI had 91.8% sensitivity, 55.2% specificity, 84.1% NPV, 72.2% PPV and AUC was 0.919 (95% CI 0.86-0.96). Conclusion: Using multiple biomarkers like P2PSA and PHI with better specificity can aid in the diagnosis of PC.