OBJECTIVETo study the correlation of activated protein C (APC) resistance, coagulation factors and inhibitors abnormality and JAK2V617F mutation burden in patients with myeloproliferative neoplasms (MPN).

METHODSThe APC resistance was defined as the ratio of activated partial thromboplastin time (APTT) in the presence and absence of APC, i.e. APC sensitivity ratio (APCsr). Plasma protein C (PC), protein S (PS), prothrombin (FII), factor V (FV), factor VIII levels and CD11b expression on neutrophils were measured. The percentage of mutated JAK2V617F allele (V617F%) was evaluated by real time polymerase chain reaction (qRT-PCR).

RESULTSExpression of CD11b on neutrophils was significantly elevated in MPN patients compared with that of the control group. APCsr, PS and FV levels were reduced in patients with MPN. The APCsr level was decreased mainly in patients with thrombosis and JAK2V617F mutant burden higher than 75%. APCsr was not only positively correlated with PS levels but also inversely correlated with JAK2V617F allele burden in JAK2V617F mutant gene carriers.

CONCLUSIONThe neutrophil was activated and PS, FV level were reduced in MPN patients. The APCsr level was decreased and the occurrence of relatively acquired APC resistance was found in MPN patients with thrombosis. The APCsr is correlated with the PS level and JAK2V617F mutational furden.