The role of immature platelet fraction in acute coronary syndrome.

Dear Sir, Activated platelets play a crucial role in the pathogenesis of acute coronary syndrome (ACS) (1), and platelet size can be a determinant of platelet function. Thus, large platelets are metabolically more active than small platelets and have greater pro-thrombotic potential (2). However, the clinical influence of platelet size, measured as mean platelet volume (MPV), is controversial (3–6). An alternative to MPV measurement is the analysis of immature platelet fraction (IPF). Newly formed platelets can be distinguished from mature platelets that are poor in RNA by flow cytometric quantification using fluorescent dyes that bind RNA (7). However, this method produces high intra-assay reproducibility coefficients of variation (8) and requires specialist personnel to perform it. A new, rapid and fully automated method for the measurement of reticulated platelets, expressed as the immature platelet fraction (IPF), using the Sysmex XE-2100 blood cell counter has been under development. Recently, Grove et al showed that measurements of IPF made with the Sysmex XE-2100 were significantly higher in patients with ACS than in healthy subjects (9), although further studies were required. Therefore, the aim of this study is to examine the relationship between IPF and ACS in a case-control study. A total of 404 individuals were enrolled in the study. A total of 202 patients with a documented first episode of ACS were prospectively recruited upon admission to the Coronary Unit. The diagnosis of ACS included ST segment elevation myocardial infarction (STEMI, n = 129) and non-ST segment elevation ACS (NST ACS, n = 73). The latter group included non-ST segment elevation myocardial infarction (NSTEMI) and unstable angina (UA) patients. Diagnosis of STEMI, NSTEMI and UA was made according to the new ESC/ACC consensus definition (10). The control group for our study included 202 unrelated healthy persons without a history of vascular or thromboembolic disease and a normal electrocardiogram. All subjects gave their informed consent to enter the study. Blood was collected from the antecubital vein at 08:00 a.m. on day 1 or 2 after admission. IPF was calculated as the ratio of immature platelets to the total number of platelets in a fully automated haematology analysis system (Sysmex XE-2100; Sysmex,