COVID-19 has elicits a rapid spread of outbreak with the human-to human transmission [19, 20]. COVID-19 pneumonia patients on early stage were not very severe. In initial of sever stage, patients show severe pneumonia and passed away on 7–14 days, considering that there are several controversial declarations about predictive indices for COVID-19 severe illness has been published so far, a necessary need for prediction of progression chance of COVID-19 is felt and more investigations is pivotal in this regards. Recently, it has been documented that the NLR level, as a novel inflammatory index, is as an early risk factor for prediction of ICU admission rate and severity of COVID-19 disease [21, 22]. As hypothesized in recent studies, patients with age ≥ 50 and NLR ≥ 3.13 is considered as severe cases and they should be bedridden in intensive care units . Also in other study it revealed that the decrease of lymphocyte count pointed to the disease progress . A large body of scientific literature has been declared that blood lymphocyte and neutrophil-related indices may be a potential predictors of this disease. For more validation of this declaration, in present study, we evaluate these indices in Iranian population of COVID-19. In recent decay, the NLR index was considered as a marker of the severity of bacterial infections .
In this study, the data of 250 patients with COVID-19 were analyzed and the laboratory indices were presented. Our results indicated that NLR factor could be one of the most significant factor affecting the severe illness. In support of our finding, Jingyuan Liu compared NLR with MuLBSTA and CURB-65 scoring models. They documented that NLR factor have higher AUC, c-index, sensitivity and specificity than the other two models . Recently, Ai-Ping Yang et al reported that elevated NLR is an independent prognostic biomarker that affected pneumonia progression in COVID-19 patients . Our results were consistent with previously published studies in respect of the relationship between NLR and prognosis of COVID-19. The following reasons may account for the findings. Regarding this findings, it could be hypothesized that immune response initiated by viral infection mostly depends on lymphocyte , whereas systematic inflammation drastically suppress cellular immunity, significantly decreasing CD4 + T lymphocytes and increasing CD8 + T lymphocyte . Another the possible mechanism for reduction of lymphocytes in COVID-19 infection is that lymphocytes are the target of virus because the angiotensin converting enzyme 2 receptor of the virus is expressed on lymphocytes, too [28, 29]. In other hand, Neutrophilia may stem from the cytokine storm initiated by virus infection [30, 31]. Thus, virus-related inflammation escalated NLR factor.
In present study, the optimal cut-off value for NLR, dNLR, SII, PWR, and PLR were observed via the ROC curve. The optimal threshold at 7.61 for NLR showed a prognostic possibility of clinical symptoms to mortality rate of disease. The highest level of AUC for predicting death in patients with COVID-19 related to PLR (0.866) with a sensitivity and specificity of 91% and 69.8% respectively. Moreover, our analysis publicized that, along with NLR, dNLR, SII, and PLR may be used as a predictive diagnostic value for determining subjects needing ICU support. Previous studies have stated that the authentication of PLR factor is required . In our study, the optimal threshold value of PLR was identified with highest sensitivity (91 %) with an acceptable specificity (69.8%). The AUC of NLR arrived the highest value (0.808) at the optimal cut-off value to predict the ICU admission (sensitivity, and specificity of NLR is 84% and 72%, respectively). Our outcomes are consistent with previous reports signifying higher NLR value as a predictive factor for severity of COVID-19 infection. Along with NLR factor, we saw the optimum AUC, sensitivity, and specificity of threshold value of dNLR (0.773, 85% and 61%, respectively), PLR (0.771, 70% and 79%, respectively) and SII (0.774, 84% and 66%, respectively). According to our results, not also NLR, but also dNLR, PLR, and SII could have prognostic value for predicting ICU admission in patients with COVID-19. The useful application of NLR, PLR, SII has been documented in many disease including tumor-related diseases [33, 34], autoimmune diseases , bacterial infectious pneumonia , and tuberculosis , secondary pulmonary infectious diseases . It has been well-documented that these indices could be able to predict survival rate and severity of above mentioned disease. However, the application of dNLR, PWR, SII in COVID-19 pneumonia was poorly reported. Based on our study and recently published documents, in could be said that NLR,PLR, dNLR, PWR and SII indicate the progression trend of COVID-19 and could be used as a prognostic value for COVID-19 condition.
Finally, the findings of this study indicated that elevated NLR was an independent prognostic biomarker for COVID-19 patients. Therefore, the applicable NLR is suggested as practical tools to evaluate the severity of COVID-19 individuals. Also, as can be seen in our findings, according to obtained values of AUC, sensitivity, and specificity for dNLR and SII parameters, it could be concluded that dNLR and SII, also could be applicable for predicting death and ICU bed management in patients with COVID-19. Another finding of this study is related to PWR index. In conjugation with other scientific reports, our obtained data showed that PWR has a reverse relation with ICU care and mortality rate of COVID-19. Because of huge medical and economic burden of COVID-19, compared with other factors, such as IL-6, NLR and other novel parameters are simple, fast and economical to achieve directly from the blood samples, and this can help clinicians identify the severe ill patients and progress rate of COVID-19 . Although prognostic value of NLR and PLR, and dNLR factors was shown recently in COVID-19 patients, in present study, we further authorized these prognostic factors in Iranian COVID-19 population. Along with, SII factor was introduced, for a first time, for prognostic aims in COVID-19 patients.