Analytical and Real‐World Clinical Characterization of S2,3PSA% Test in MRI Fusion Targeted Prostate Biopsy Population

ABSTRACT Background The α2,3‐sialyl N ‐glycosylated free prostate‐specific antigen ratio (S2,3PSA%) was approved in Japan as a prostate cancer (PCa) diagnostic test. We evaluated the analytical characterization and real‐world diagnostic performance of S2,3PSA%. Methods The precision testing, dilution linearity, measurement sensitivity, preanalytical stability, and interferences of S2,3PSA, α2,6‐sialyl N ‐glycosylated free PSA (S2,6PSA), and S2,3PSA% were performed. The diagnostic accuracy detecting PCa of S2,3PSA% was prospectively evaluated in 253 men (Cohort 1, vs. PI‐RADS) and in 145 men (Cohort 2, vs. PI‐RADS, prostate health index , phi ) who scheduled MRI‐targeted biopsy by area under the receiver operating characteristics curve (AUC). Results The precision of the S2,3PSA, S2,6PSA, and S2,3PSA% were all < 3.4% coefficient of variation. The dilution linearity of S2,3PSA had a correlation coefficient of 0.9949–0.9987. The detection limit of S2,3PSA and S2,6PSA was 0.044 and 0.029 ng/mL, respectively. Serum S2,3PSA and S2,6PSA concentrations were stable at 6°C for 24 h and −20°C for 90 days, while S2,3PSA% was unchanged at 6°C and −20°C for 90 days or under five freeze–thaw cycles. Serum S2,3PSA and S2,3PSA% were not affected by any interferences and drugs. In Cohort 1, AUC of S2,3PSA% (0.776, 95% CI 0.719–0.832) detecting PCa was comparable to that of PI‐RADS (0.746, 0.685–0.807, p  = 0.7996). In Cohort 2, AUC of S2,3PSA% detecting PCa (0.837, 0.774–0.901) was comparable to PI‐RADS (0.779, 0.703–0.854, p  = 0.3037), and phi (0.867, 0.809–0.926, p  = 0.3000). Conclusions Analytical characteristics of S2,3PSA% perform well and the diagnostic performance of S2,3PSA% was comparable to phi and MRI.