Letter to the editor: mean platelet volume and diabetic retinopathy

Abstract

Dear Editor, We read with great interest the article by Ayhan Tuzcu et al. about the relationship between mean platelet volume (MPV) and retinopathy in patients with type 2 diabetes mellitus [1]. The authors performed a study aimed to evaluate the effect of MPVon diabetic retinopathy in patients with type 2 diabetes mellitus. They suggested that the risks of development of diabetic retinopathy and proliferative diabetic retinopathy increase with higher MPV values. We would like to discuss this study. The sentence of “MPV is a parameter of platelet function” does not reflect the current literature. The MPV and/or other platelet indices are not used as platelet function tests [2]. Light transmission aggregometry is the gold standard for the study of patients with defects of platelet function [3]. Beyan et al. investigated whether platelet indices have a correlation with functional aggregation responses using optical method in healthy adults, and evaluated the predictive significance of platelet indices over platelet aggregation responses [4]. They did not find any correlation between platelet aggregation responses obtained with turbidometric platelet aggregometry and platelet indices including platelet count, MPV, platelet distribution width, and plateletcrit proposed as indicators of certain pathologic conditions, and it does not seem possible to use platelet indices as a direct indicator of platelet function. Accurate measurements of platelet count and size are important for diagnostic, therapeutic, and research purposes. Lance et al. reviewed the preanalytical variability of the MPV, and proposed a possible approach to standardization [5]. MPV does not routinely use a part of the complete blood count because of the ethylenediaminetetraacetic acid (EDTA)induced changes over time [6]. EDTA-induced platelet shape changes result in a progressive increase in MPV with impedance technology. In general, the MPV increases up to 30 % within 5 min of exposure, and increases further by 10 to 15 % over the next 2 h [7]. Some investigators have reported variable increases in MPV with EDTA storage up to 50 % [6]. The effect of EDTA on MPV with optical analysis is less well-documented, but appears to be unpredictable, decreasing in many patient samples and increasing in others [6]. Lance et al. performed a study to standardize the measurements of MPV. They suggested that timing is important when measuring the MPV, and that the optimal measurement time should be 120 min with EDTA after venipuncture [8]. Furthermore, different technologies for measuring the MPV give different results. Studies comparing results from different instruments have shown MPV variability up to 40 % [6]. The MPV measurement time, the MPV measurement method, and using technologies for the measurement of MPV were not described in this retrospective study. As a conclusion, theMPVmeasurement protocol should be standardized before the using of MPV for diabetic retinopathy in patients with type 2 diabetes. C. Beyan (*) Department of Hematology, Gulhane Military Medical Academy, Etlik, 06018 Ankara, Turkey e-mail: cbeyan@gata.edu.tr