The relationship between platelet indices and postmenopausal osteoporosis.

Abstract

Dear Editor, I read with great interest the article published by Akbal et al. [1], in which the authors assessed platelet indices in postmenopausal osteoporosis patients. Mean platelet volume (MPV) and platelet distribution width in the osteoporosis group were lower than in the normal bonemineral density group. I congratulate the authors on the contribution of their well designed and documentedd study. However, I would like to make a minor criticism of this study from a methodological viewpoint. The authors screened complete blood counts, biochemical and thyroid tests in postmenopausal patients, with bone mineral density measurements performed retrospectively between 2011 and 2013; however, they made no mention of the MPV measurement technique used. Accurate measurements of platelet count and volume are important for diagnostic, therapeutic, and research purposes. The choice of anticoagulant [ethylenediaminetetraacetic acid (EDTA) or citrate], time interval of measurement, and temperature at which MPV is analyzed are important factors in MPV measurement. The time-dependent swelling of platelets in samples anticoagulated with EDTA can result in an artefactual increase in MPVand misinterpretation of prothrombotic changes [2]. In actual daily practice, MPVmeasurements are performed at room temperature and temperature factors can be negligible. However, the choice of anticoagulant and time interval ofMPV measurement are an important issue. MPV increases over time in EDTA-anticoagulated samples and this increase was shown to be proportional with the delay in time between sample collection and laboratory analysis. With impedance counting, MPV increases over time as platelets swell in EDTA, with increases of 7.9 % within 30 min having been reported, and an overall increase of 13.4 % over 24 h, although the majority of this increase occurs within the first 6 h [2]. Dastjerdi et al. [3] recommended that MPV be measured within 1 h regardless of anticoagulant. Lance et al. [2] reported that optimal stability was detected in K2-EDTA after 120 min. It is widely accepted that platelet swelling in test tubes can be minimized by rapid processing of samples (within less than 1 h) [3]. For reliable MPV measurement, the potential influence on the MPVof the EDTA anticoagulant must be controlled carefully by standardizing the time delay between sampling and analysis. Secondly, there are significant associations of MPV with many cardiovascular risk factors, such as smoking, obesity, hypertension, diabetes mellitus, prediabetes, hyperlipidemia, metabolic syndrome, atrial fibrillation and fatty liver disease [4]. The authors did not mention data on the body mass index, metabolic syndrome, rhythm status and fatty liver disease in the patients and controls. It has been shown that obesity, metabolic syndrome, atrial fibrillation and fatty liver disease increase MPV values [4]. Absolutely, these factors should be considered in MPVassessment. There seem to be hyperlipidemic patients in the three groups studied, but there is no mention of statin use in these hyperlipidemic patients. There are also significant associations of MPV with statin use, with statins having been shown to decrease MPV [5]. It would have been useful if the authors had provided information on these factors. MPV is universally available with routine blood counts by automated hemograms and is a simple and easy method of assessing platelet function. In comparison to smaller platelets, larger platelets have more granules, aggregate more rapidly with collagen, have higher thromboxane A2 levels and express more glycoprotein Ib and IIb/IIIa receptors [2, 4]. MPV can be affected by many cardiovascular risk factors. A response to these comments can be found at doi: 10.1007/s00198-0153047-8.