Value of combination of the neutrophil to lymphocyte ratio and platelet to lymphocyte ratio in primary percutaneous coronary intervention

We read with interest the article by Ayca et al. [1] that assessed the prognostic value of the platelet to lymphocyte ratio (PLR) in primary percutaneous coronary intervention (pPCI). They concluded that the PLR could predict no-reflow, severity of coronary artery disease (CAD) and in-hospital mortality in patients undergoing pPCI. They also suggested that the PLR is a novel marker of prognostic value. We would like to share our experience with Ayca et al.

First, as indicated in the original study, some clinical conditions which may affect platelet and lymphocyte counts were excluded to avoid possible confounders for the PLR. Several studies reported that a high PLR may reflect ongoing vascular inflammation and play a role in the pathophysiology of hypertension (HT), diabetes mellitus (DM) and prediabetes [2, 3]. However, subjects included in the original study were not evaluated in terms of DM and HT. In addition, although it is noted that patients with infection or systemic inflammatory conditions were excluded, patients with elevated white blood cell (WBC) count (11.1 ± 2.6 and 12.6 ± 4.4 in patients with low and high PLR, respectively) were included. In studies aimed to determine predictive markers, it would be better to identify a specific WBC count range within the exclusion criteria [4]. Although a high WBC count is not specific to a disease, it can indicate infection, stress, inflammation, trauma, allergy or certain diseases [5]. Moreover, the WBC reference ranges may vary depending on the factors such as the population studied, the individual laboratory (e.g. type of collection tubes) or measurement methods used (e.g. time prior to analysis) [5].

Second, in the original study [1], a lower lymphocyte count is associated with high mortality rate in AMI due to increased cortisol stress response. Decreased lymphocyte count has been associated with malnutrition [6]. However, the nutritional status of the participants has not been evaluated and there is no effective laboratory indicator identifying malnutrition as the cause of lymphopenia in the original study [7]. Serum proteins, particularly albumin, have been used to assess malnutrition. Albumin has a relatively long half-life, approximately 14–20 days, and because of this, has been proposed as a marker of chronic nutritional status [8]. Therefore, it would be useful to at least assess albumin levels and evaluate the correlation between albumin levels and lymphocyte count in the current study.

Third, as presented in Table III of the original study, the neutrophil to lymphocyte ratio (NLR) was similar and even more significant than the PLR in multivariate logistic regression analysis which was performed to identify independent predictors of no-reflow, Syntax scores (SXS) and in-hospital adverse events. Moreover, in another study, the combination of PLR and NLR exhibited the best diagnostic performance for the prediction of in-hospital and long-term mortality in patients undergoing pPCI [9]. Therefore, performing receiver operating characteristic analyses to detect the cut-off value of NLR in the prediction of no-reflow, SXS and in-hospital adverse events and performing cumulative survival curves according to combined NLR and PLR risk stratification would improve the significance of the study.

Declaration of interest

The authors report no conflicts of interest.