To the editor,
We read with great interest the article‘‘Evaluation of mean platelet volume (MPV) levels in patients with synovitis associated with knee osteoarthritis (OA)” by Balbaloglu et al. [Citation1]. This study assessed the MPV, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels in patients with synovitis associated with knee OA. They demonstrated a significant relationship between MPV and ESR in this patient group and CRP values were significantly different between the control group and OA-knee synovitis group. The authors (1) suggested that MPV levels may be considered as a marker of inflammation but further comprehensive prospective trials are needed in synovitis associated with OA.
OA is the common arthropathy with marked heterogeneity of clinical presentation. The diagnosis of OA may be made without recourse to radiographic or laboratory investigations in the at-risk age group with typical symptoms and signs [Citation2]. Although OA has been considered as a non-inflammatory disease compared with rheumatoid arthritis, evidence has demonstrated a low grade of inflammation mainly associated with synovitis [Citation3]. Chronic inflammatory changes with production of proinflammatory cytokines are a feature of synovial membranes from patients with early OA. This low-grade synovitis results in the production of cytokines that may contribute to the pathogenesis of OA [Citation3]. Body mass index (BMI) could influence the association between inflammatory markers and muscle strength in knee OA [Citation4]. For this reason, we think that because platelet function can be affected by obesity [Citation4], further studies should consider BMI in these patients.
A complete blood count is a routine, easy and cheap examination that provides additional information in many aspects. MPV is a widely used laboratory marker associated with platelet function based on inflammatory conditions [Citation5, Citation6]. The MPV also represents platelet function, which is central to processes that are involved in coronary heart disease pathophysiology and endothelial dysfunction [Citation7–9]. Platelet parameters might be influenced by coronary risk factors including age, obesity, smoking, diabetes mellitus, hypertension, hyperlipidemia, metabolic syndrome and deep vein thrombosis [Citation6, Citation10]. Another study has demonstrated that MPV can predict stroke [Citation11]. Some other recent studies have reported that an elevated MPV is linked with peripheral artery disease and stroke, all of which are related to atherosclerosis on the basis of inflammation [Citation5]. Previous studies demonstrated an association between long-term mortality after non-ST-segment elevation myocardial infarction and peripheral blood platelet indices including MPV and platelet count [Citation12]. The MPV can also be affected by thyroid and rheumatic diseases [Citation13, Citation14], malignancy and medications such as anticoagulant therapy and statins. So, we think that if the authors mentioned these factors, it might be useful.
The MPV is a marker of inflammation. A previous study showed significant MPV differences in patients with hepatic diseases [Citation15]. Furthermore, MPV value was higher in chronic obstructive pulmonary disease patients compared to controls [Citation16, Citation17]. Therefore, it would be interesting if the authors [Citation1] provided information about hepatic function tests and respiratory conditions of these patients.
Platelets undergo a time-dependent swelling when blood samples are anticoagulated with EDTA [Citation18]. Therefore, the authors [Citation1] should describe how the blood samples were taken. Furthermore, the MPV may be affected by several factors. MPV itself alone without other overt inflammatory markers may not provide information about the chronic endothelial inflammatory condition of the patient. So, the MPV should be evaluated together with other inflammatory markers like neutrophil lymphocyte ratio [Citation19] and red cell distribution width [Citation20]. We believe that these findings will guide further studies about MPV as a surrogate marker of endothelial dysfunction and inflammation in patients with OA.
Declaration of interest
There is no conflict of interest.
References
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