Neutrophil Lymphocyte Rate: A Marker of Mortality and Prognosis for Covid-19?

Objective: In recent years, the neutrophil-to-lymphocyte ratio (NLR) has become a parameter sought in the prediction of aggressive prognosis or mortality in many studies including sepsis, infectious diseases, and malignancies. There are publications studying the correlation between the high values of this parameter, which can be interpreted as an indirect indicator of the host’s immune response, in the COVID-19 infection with mortality. The primary objective of our study is to evaluate the correlation between the height of NLR values in the patients followed up in our intensive care units (ICU) with the final diagnosis of COVID-19 infection (PCR(+)), the continuation of such high values throughout the treatment and mortality, and finally obtain a cut-off value in predicting the prognosis.Method: The case files with final diagnosis of COVID-19 infection followed up and treated in our 3rd Level Intensive Care Unit from 21 March 2020 to 1 July 2020 were screened retrospectively and included in the study. These cases were examined in two groups: exitus (n=113) and survivors (n=70). The demographics of the cases such as age, gender, comorbid diseases as well as their vital signs and clinical and laboratory features were screened from the Hospital Operating System (HOS) and archive files, and recorded. The correlation among the data obtained as well as the correlation between such data and mortality were analyzed.Findings: In the study conducted on 183 cases, the ages, APACHE II scores, admission NLR values, study endpoint NLR values, neutrophil, procalcitonin, D-dimer, PT and INR levels, and MV (Mechanical Ventilation) durations of the exitus cases were found statistically significantly higher than the survivor cases. In the exitus cases, the cut-off point found for the admission NLR was >7.82. During the course of treatment, the patients with high NLR level had poor prognosis. The patients’ NLR values at the study endpoint were analyzed. The conclusion is that >6 as the cut-off point value is significant from the viewpoint of mortality. In addition, it was observed that a NLR level over 6 despite the treatment increased the mortality rate by 15.6 times. Conclusion: We have found out that old age, long MV duration, prolonged high levels of D-dimer, neutrophil, PT, INR and NLR levels increase the mortality rate. Being able to predict the course of prognosis and using early warning systems will increase the survival rate. In this regards, we consider closer monitoring of the patients with high NLR level, particularly in the intensive care units even if they do not have respiratory distress, will decrease mortality significantly. NLR can help identifying the COVID-19 patients with high risk level. High NLR level during the intensive care monitoring process may be regarded as insufficient immune response, and thus correlated with mortality and aggressive prognosis.