Free vs total pregnancy-associated plasma protein A (PAPP-A) as a predictor of 1-year outcome in patients presenting with non-ST-elevation acute coronary syndrome.

Background: The free fraction of pregnancy-associated plasma protein A (FPAPP-A) was found to be the PAPP-A form released to the circulation in acute coronary syndrome (ACS). We estimated the prognostic value of FPAPP-A vs total PAPP-A (TPAPP-A) concentrations in forecasting death and nonfatal myocardial infarction (combined endpoint) in patients with non-ST-elevation ACS.
Methods: We recruited 267 patients hospitalized for symptoms consistent with non-ST-elevation ACS and followed them for 12 months. FPAPP-A, TPAPP-A, C-reactive protein (CRP), and cardiac troponin I (cTnI) were measured at admission; cTnI was also measured at 6-12 h and 24 h. Because of the recently shown interaction between PAPP-A and heparin, we excluded patients treated with any heparin preparations before the admission blood sampling.
Results: During the follow-up, 57 (21.3%) patients met the endpoint (22 deaths and 35 nonfatal myocardial infarctions). According to FPAPP-A (<1.27, 1.27-1.74, >1.74 mIU/L) and TPAPP-A (<1.98, 1.98-2.99, >2.99 mIU/L) tertiles, this endpoint was met by 12 (13.5%), 18 (20.2%), 27 (30.3%) (P = 0.02), and 17 (19.1%), 17 (19.1%), 23 (25.8%) (P = 0.54) patients, respectively. After adjusting for age, sex, diabetes, previous myocardial infarction, and ischemic electrocardiogram (ECG) findings, FPAPP-A >1.74 mIU/L [risk ratio (RR) 2.0; 95% CI 1.0-4.1, P = 0.053), increased cTnI, and CRP >/=2.0 mg/L were independent predictors of an endpoint. The prognostic performance of TPAPP-A was inferior to that of FPAPP-A.
Conclusions: FPAPP-A seems to be superior as a prognostic marker compared to TPAPP-A, giving independent and additive prognostic information when measured at the time of admission in patients hospitalized for non-ST-elevation ACS.