Elena Zapata-Arriaza, MD

Nam K-W, Kim TJ, Lee JS, Kwon H-M, Lee Y-S, Ko S-B, et al. High Neutrophil-to-Lymphocyte Ratio Predicts Stroke-Associated Pneumonia. Stroke. 2018

Medical and neurological complications, including pneumonia, are found to be major causes of death and morbidity after stroke. Stroke-Associated-Pneumonia (SAP) incidence in stroke units ranges from 3.9% to 44%. Several clinical risk factors and predictive models for SAP have been studied. In this article, the authors’ goal is to demonstrate the relationship between the neutrophil-to-lymphocyte ratio (NLR) and SAP in acute ischemic stroke patients, as a novel biomarker predictor.

This article is based on a consecutive stroke registry in two large centers in Korea, in which the authors evaluated acute ischemic stroke patients who were admitted within seven days of the onset of symptoms. SAP was defined according to the modified Centers for Disease Control and Prevention criteria. Final results showed SAP rates of 9%, which is similar to previously reported. In addition, the SAP group had a significantly higher NLR than those of the non-SAP group (3.87 [2.09-6.66] versus 2.35 [1.59-3.81], P < 0.001). Furthermore, using a multivariate logistic regression analysis, the NLR [adjusted OR (aOR) = 1.55; 95% confidence interval (CI), 1.14-2.10, P = 0.005] remained significant after adjusting confounders. Another relevant finding of this article is the increased prediction power of NLR after A2DS2 score addition. The area under the curve of the A2DS2 score was 0.838 (0.816–0.859), which was increased after the NLR was combined with the A2DS2 score (0.858 [0.837–0.878]; P=0.047). Finally, the authors found a close correlation between the NLR and pneumonia severity, length of hospital admission, three months mRs score, discharge NIHSS score and 30-day mortality rate.

It is well known that post-stroke immunosuppression triggered after ischemic brain damage is related to the development of SAP. The originality of this paper is first NLR assessment in an SAP sample, and the ability of mentioned NLR in high-risk SAP patients selection, which could  provide clues for further studies about preventive antibiotic therapy. The easy and handy NLR performance allows an extensive use of this study’s results in daily clinical practice to select high-risk patients to begin intervention in time.

Up to now, multiple clinical and laboratory risk factors for SAP have been identified; however, the identification of NLR as SAP biomarker predictor supports the previously described stroke induced immunosuppression. Although further studies are needed, the added predictive value of NLR to A2DS2 score sets an important screening tool for SAP patients.