LAUSR

We read with great interest the retrospective study of Demirbaş et al. was to investigate various complete blood count parameters in patients with vitiligo [1]. We would like to emphasize the different factors that directly influenced the results of this study regarding platelet parameters. The researchers stated that plateletcrit (PCT) values were significantly higher in patients with vitiligo, while mean platelet volume (MPV) values did not change significantly. PCT, expressing the volume occupied by platelets in the blood, is calculated by a formula: PCT = platelet count × MPV/10,000 [2]. Therefore, PCT values are directly related inversely with MPV values. It has been claimed by the researchers that MPV shows disease activity and prognosis in various chronic diseases; on the contrary, it is not recommended to use MPV values for purposes such as diagnosing or determining prognosis in acquired diseases due to the fact that measurement standardization has not been achieved [3]. The main factors affecting the standardization in MPV measurement are the time from blood collection to MPV measurement, which anticoagulant is used in the measurement and which devices are used for MPV measurement [4–6]. When using ethylenediaminetetraacetic acid as an anticoagulant, the change in the time from blood collection to MPV measurement causes deviations of up to 2–50% in MPV values [4–6]. Depending on the device on which MPV measurement is made, deviations of up to 40% can be observed [6–8]. In the study of Demirbaş et al., it was not specified in which standards and with which devices the complete blood count measurements were made, and this situation significantly adversely affects the reliability of MPV and related PCT data. In addition, the retrospective nature of the study prevented the exclusion of analysis-related errors, and the importance of strictly ruling out analysis-related errors, especially for MPV measurements, has been emphasized before [9]. On the other hand, platelet count, MPV and PCT parameters are interrelated parameters; while there was no statistical difference between the platelet count and MPV values of the patient and control groups in this study, it is surprising that there was a significant difference between PCT values. As a result, PCT values may not be higher in patients with vitiligo.