Development of a Sensitive and Specific Immunological Test for Detecting Pregnancy-Associated Plasma Protein A in Patients with Acute Coronary Syndrome

Background: Pregnancy-associated plasma protein A (PAPP-A) was first found in the serum of pregnant women and then found to be associated with acute coronary syndrome (ACS). Unfortunately, the sensitivity and specificity of current detection methods are poor, so the present work aimed to improve them. The successful detection of PAPP-A could be widely applicable clinically. Methods: We used affinity chromatography to purify the PAPP-A antigen, which was used to prepare the antibody. A biotin-avidin enzyme-linked immunosorbent assay (BA-ELISA) was developed to detect low levels of PAPP-A. Nonspecific reactions were excluded by using affinity chromatography and papain digestion to remove the Fc fragment of the antibody. Results: The BA-ELISA method we developed was more sensitive than traditional ELISA, as all nonspecific reactions were excluded. Its sensitivity was 0.065 mIU/L and recovery of PAPP-A from samples was 98.51%. The specificity was also much better than with standard ELISA kits. Conclusions: Affinity chromatography and papain digestion have important effects on the assay specificity. The BA-ELISA method proved sensitive and nonspecific reactions were excluded. The method is easily carried out, so it is suitable for detecting PAPP-A in the serum of patients with ACS.