Dear Editors,
Neutrophil-to-lymphocyte ratio varies with patient age and body mass index.Reference Li, Chen, Luo, Hong, Pan and Lin1 Therefore, in our study, there was no difference between the body mass indices and mean ages of the groups (p = 0.20 and p = 0.415 respectively). The neutrophil-to-lymphocyte ratio is now accepted as a significant predictor of adverse clinical outcomes, and various studies have found neutrophil-to-lymphocyte ratio to be a reliable biomarker in oncology,Reference Walsh, Cook, Goulder, Justin and Keeling2, Reference Sarraf, Belcher, Raevsky, Nicholson, Goldstraw and Lim3 cardiology,Reference Tamhane, Aneja, Montgomery, Rogers, Eagle and Gurm4, Reference Nunez, Nunez, Bodi, Sanchis, Miñana and Mainar5 and several other diseases accompanied by systemic inflammation such as Alzheimer's disease, ulcerative colitis, appendicitis and chronic kidney disease.Reference Kuyumcu, Yesil, Ozturk, Kizilarslanoğlu, Etgül and Halil6–Reference Solak, Yilmaz, Sonmez, Saglam, Cakir and Unal9 The standard cut-off value of neutrophil-to-lymphocyte ratio was not stated in these studies either. These studies compared the groups as we did in our study. The cut-off values of neutrophils and lymphocytes are known. A meta-analysis of the studies covering neutrophil-to-lymphocyte ratio would need to be conducted to define a standard cut-off value of neutrophil-to-lymphocyte ratio.
Neutrophil-to-lymphocyte ratio has started to be used in systemic inflammatory diseases, including those that implicate interleukin (IL)-6, IL-10, IL-1α, tumour necrosis factor-α and other inflammatory cytokines.Reference Mehra and Redline10–Reference Shamsuzzaman, Winnicki, Lanfranchi, Wolk, Kara and Accurso12 Moreover, it may show variability in inflammatory conditions, as do other cytokines. For this reason, more studies have been conducted in recent years examining the association of neutrophil-to-lymphocyte ratio with inflammation.Reference Li, Chen, Luo, Hong, Pan and Lin1–Reference Solak, Yilmaz, Sonmez, Saglam, Cakir and Unal9
The results of our study demonstrated that the neutrophil-to-lymphocyte ratio values had a positive correlation with the severity of obstructive sleep apnoea syndrome (OSAS). The neutrophil values increased (p = 0.009) and lymphocyte values decreased (p = 0.0005) as OSAS severity increased. Hence, the neutrophil-to-lymphocyte ratio values increased linearly compared to OSAS severity (p = 0.0008). The results of our study suggested that the neutrophil-to-lymphocyte ratio, which increases as a consequence of systemic inflammatory response in OSAS, will be significant in the clinical follow up of OSAS patients. We advocate performing the neutrophil-to-lymphocyte ratio as an auxiliary diagnostic method in all patients. However, we do not think this measure could replace polysomnography. A polysomnographic evaluation is required for the diagnosis of OSAS. Polysomnography is also used to decide whether continuous positive airway pressure (CPAP) is required, and for planning the CPAP treatment protocol.
We thank the author for his contribution and opinion.
