Dear Editor, the recent report on “Neutrophil-to-Lymphocyte Ratio (NLR), Platelet-to-Lymphocyte Ratio (PLR) and Heart Failure” is very interesting.1 Durmus et al.1 reported that “NLR can be used to predict mortality during the follow-up of HF patients.” Indeed, the use of a new parameter for predicting heart failure is very interesting. However, as Durmus et al.1 mentioned, both NLR and PLR “were not sufficient to establish a diagnosis of HF.” In addition, although the present report1 was well designed as a matched case-control study, the problem on NLR and PLR should be discussed in view of laboratory medicine. Both parameters are non - specific. Several factors can affect neutrophils, lymphocytes and platelets. Other concomitant disorders such as immunological and malignant disorders can alter the NLR and PLR values.2-3 Also, metabolic syndrome, which is common among the patients with cardiac disease, can also affect NLP and PLR values.4 In addition, different automated hematological analyzers can also give different results of neutrophil, lymphocyte and platelet measurements.5