A new method to measure plasma levels of activated protein C in complex with protein C inhibitor in patients with acute coronary syndromes

Our newly devised immunofluorometric. sandwich assay for measuring plasma c oncentrations of activated protein C (APC) in complex with protein C inhibi tor (PCI) was compared with testing for conventional markers of myocardial damage CKMB. (creatine kinase MB), TNI (troponin I) and hypercoagulability (D-dimer, TAT) in 76 patients with suspected myocardial infarction (MI). AP C-PCI complex levels in samples drawn on admission did not correlate with C KMB in the simultaneously drawn sample but correlated closely with maximal CKMB, which reflects MI size (r = 0.52). The areas under the receiver opera ting characteristics (ROC) curves calculated for the APC-PCI complex result s obtained upon admission did not differ significantly from the correspondi ng values for CKMB, TNI or TAT. Our results show that in patients at risk f or MI, the APC-PCI concentration is a sensitive and independent marker that can identify a subgroup of MI patients with normal CKMB but an increased A PC-PCI level upon admission. It remains to be determined whether these pati ents would benefit from early intensive anticoagulant treatment. (C) 2001 L ippincott Williams & Wilkins.