Abstract
We have read the article published by Erdem et al with a great interest. 1 They have examined whether red cell distribution width and mean platelet volume (MPV) values differ between patients with reactive amyloid A (AA) amyloidosis due to chronic inflammatory disease and healthy controls. They have found red cell distribution width, erythrocyte sedimentation rate, and platelet count levels to be significantly higher in patients with AA amyloidosis compared to the controls and MPV was significantly lower in patients with amyloidosis. This is the first study in this subject. On the other hand, we want to mention minor criticism about this study from the methodological aspect.
First, they did not mention about the time between blood sampling and analysis. They used EDTA-anticoagulated tubes for sample collection. However, 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, the MPV increases over time as platelets swell in EDTA, with increases in 7.9% within 30 minutes having been reported and an overall increase in 13.4% over 24 hours, although the majority of this increase occurs within the first 6 hours. 2 The recommended optimal measuring time of MPV is maximum 120 minutes after venipuncture. For reliable MPV measurement, the potential influence of anticoagulant on the MPV must be carefully controlled by standardizing the time delay between sampling and analysis (less than 2 hours). This situation is not clear in study.
Second, there are significant associations of MPV with smoking, obesity, coronary artery disease, metabolic syndrome, statin use, and atrial fibrillation. 3,4 They did not mention about the body mass index of patients and controls, smoking status, coronary heart disease, proportion of patients and controls with metabolic syndrome, rhythm status, and proportion of patients and controls using statin. If we look at the low-density lipoprotein cholesterol levels, there are high values such as 373 mg/dL in the patient group and such as 196 mg/dL in the controls. So, there can be patients and controls using statin. Higher MPV values were reported in smokers and in patients with obesity, coronary artery disease, metabolic syndrome, and atrial fibrillation. On the other hand, statin treatment decreases MPV. 4 These situations are not clear in the study.