Comparison of oligonucleotide-labeled antibody probe assays for prostate-specific antigen detection.

As a specific tumor marker, prostate-specific antigen (PSA) is widely used for the early diagnosis of prostate cancer. Sensitive and specific methods are required to improve the diagnostic accuracy of PSA detection. In the current study, we compared the immuno-polymerase chain reaction (immuno-PCR) method with the solid-phase proximity ligation assay (SP-PLA) with respect to the detection of PSA. Using oligonucleotide-labeled antibody probes, we used both immuno-PCR and SP-PLA to detect trace levels of PSA. The nucleic acid sequences can be monitored using real-time PCR. SP-PLA, however, was found to be superior in terms of both the detection limit and the dynamic range. To detect even lower levels of PSA, we used the loop-mediated isothermal amplification (LAMP) method to measure the levels of reporter DNA molecules in SP-PLA. The sensitivity of the LAMP method is 0.001 pM, which is approximately 100-fold higher than the sensitivities of the other assays. The results suggest that an SP-PLA- and LAMP-based protocol with oligonucleotide-labeled antibody probes may have great application in detecting PSA or other proteins present at trace levels.