Mean platelet volume in patients with type 2 diabetes mellitus (Authors’ reply)

Sir: We thank Drs Jagroop and Mikhailidis for their kind interest in our work. In which the association between mean platelet volume (MPV) and diabetic complications was evaluated [1]. Measurements were carried out using two cell counters, Sysmex SF 3000 and Cell-Dyn 3700, their resolution being 0.2 fl [1]. Certainly, these counters have a poorer resolution than the channalyzer employed by Mikhailidis et al. [2]. Overall, MPV was higher than previously reported [2, 3]. The MPV of diabetic patients is significantly higher than that of healthy volunteers [1, 4], though not as high as in our study [1]. However, MPV in patients with diabetes mellitus is also influenced by the presence of diabetic complications [1, 4]. Indeed, retinopathy [1, 4] and microalbuminuria [1] have been found to increase MPV. The majority of diabetic patients in our study had microvascular complications (retinopathy or microalbuminuria) [1]. Hence, it may be argued that higher MPV in comparison to earlier studies is attributable to the higher prevalence of diabetic complications. The impact of further diabetic complications (neuropathy, for instance) on MPV is currently being investigated by our group. By increasing MPV in patients with diabetes, diabetic complications might also be expected to result in a greater difference in platelet volume between diabetic and non-diabetic groups. MPV in our study was not associated with HbA1c [1], in keeping with the previous report by Sharpe and Trinick [4]. Fasting plasma glucose levels in our study were 183.5 10.2mg/dl and they were not associated with MPV. This is in accordance with earlier work showing that platelet activation in diabetic patients does not depend on glycaemic control [5, 6]. Furthermore, Tschoepe et al. have shown that long-term glycaemic control does not lead to reduced platelet activation [7]. There seems to be no doubt that MPV may prove a valuable indicator of platelet activation and that further experience is warranted before it is put into everyday clinical practice. This application would, presumably, be of particular benefit for diabetic patients.