Dear editor, we read the publication on “Prognostic significance of preoperative and follow-up neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in patients with non-metastatic clear cell renal cell carcinoma (NMCCRCC)” with a great interest [1]. In this work, preoperative NLR (pNLR) and PLR (pPLR) and relationship with recurrence-free survival (RFS) are studied. Kim et al. [1] concluded that “pNLR and pPLR are independent prognostic factors for RFS in patients with NMCCRCC.” There are some considerations on the use of pNLR and pPLR. Both pNLR and pPLR might be affected by several confounding factors and this might be pitfall of the present study. This problem is the basic forgotten problem for clinical use of NLR and PLR as prognostic factors in several medical disorders [23]. Focusing on basic laboratory medicine principle, the neutrophil, lymphocyte and platelet investigation needs good quality control and the parameters from different analyzers might be variable [4]. The results of differential white blood counts of the same patient's sample from different analyzers are usually different [4]. For example, the result of neutrophil count performed by some analyzers comparing to manual referencing count might be lower [5].

We thank the authors of the letter to the Editor for their important comments. We agree that the results of differential white blood counts may vary from analyzer to analyzer. This is perhaps one of the reasons why investigators present different cutoff neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) values that separate patients with better prognosis and worse prognosis. So, making a one-size-fits-all cutoff is useless. However, this variability does not eliminate the importance of differential counts used every day in practice. It is up to clinicians to interpret and apply these values after adjusting for their specific working environment. The same is true for NLR and PLR values in patients with renal cell carcinoma.