**4. Discussion**

This study represents a review of the COVID-19 deaths at Sukraraj Tropical and Infectious Disease Hospital during the first wave of coronavirus pandemic in Nepal from early 2020 till early 2021. Patients with underlying diseases and age over 65 years made up the majority of deaths, similar to demographics of COVID-19 deaths from other studies [10–13]. Du et al. performed a single center prospective cohort study to investigate the possible risk factors associated with the poorest clinical outcome (dying from COVID-19 pneumonia) and reported that age ≥65 years to be one of the predictors for mortality in COVID-19 [10]. The current study also suggested that old age was associated with deaths in patients with COVID-19. Age as a determinant for prognosis could be due to poor health and associated comorbidities. This signifies the need for aggressive monitoring and intensive treatment strategies to be employed at the earliest to limit deaths in older age population. Further, prophylactic treatments in anticipation of the disease in the elderly could involve natural repetitive stimulations of the heat shock response in the whole body through controlled intense physical exercise, sauna therapies and the regular maintenance of calorie-restricted diets containing minimal amounts of saturated lipids and cholesterol [14].

Recent studies revealed lymphocytopenia as an important characteristic of SARS-CoV-2 infection, especially in critically ill and deceased patients [11,12]. Huang et al. and Wang et al. showed an association between lymphocytopenia and need of intensive care unit [1,13]. Similarly, Wu et al. showed an association between lymphocytopenia and acute respiratory distress syndrome (ARDS) development [15]. In Singapore, Fan et al. found that patients requiring ICU support had significantly lower lymphocyte levels at baseline [16]. Similar to these studies, our study also showed that the majority (80%) of patients who died had lymphocytopenia at presentation. Thus, lymphocytopenia can be

taken as one of the severity markers of COVID-19 and we need to be vigilant in patients presenting with lymphocytopenia.

A meta-analysis of nine studies suggested that thrombocytopenia is significantly associated with the severity of COVID-19 disease; a more sizeable drop in platelet counts was noted especially in non-survivors [17]. In our study, significant proportion (42%) of cases that died had thrombocytopenia at presentation. A systematic review and metaanalysis by Li et al. concluded that NLR has significant predictive value for disease severity and mortality in patients with COVID-19 infection [18]. Similarly, Liu Y et al. showed that NLR is an independent risk factor of the in-hospital mortality for COVID-19 patients [19]. A retrospective cross-sectional study done by Yan et al. showed that NLR more than 11.75 was significantly correlated with all-cause in-hospital mortality [20]. In our study, the majority of patients who died presented with NLR > 11.75. NLR evaluation can help clinicians identify potentially severe cases early, conduct early triage and initiate aggressive managemen<sup>t</sup> at the earliest, which may reduce the overall mortality of COVID-19.

A retrospective, multi-center cohort study from Jinyintan Hospital and Wuhan Pulmonary Hospital (Wuhan, China) showed that older age, D-dimer levels greater than 1 μg/mL and higher SOFA score on admission were associated with higher odds of inhospital death [21]. A meta-analysis done by Huang et al. also suggested that elevated serum C-reactive protein, procalcitonin, D-dimer and ferritin were associated with poor outcome in COVID-19. It showed that a D-dimer >0.5 mg/dL had 58% sensitivity and 69% specificity for severe disease [22]. In a retrospective study by Tang et al. encompassing data from 183 consecutive patients with COVID-19, non-survivors had significantly higher Ddimer (*p* < 0.05), fibrin degradation product (FDP) levels (*p* < 0.05), prolonged PT (*p* < 0.05) and APTT (*p* < 0.05) compared with survivors at initial evaluation [23]. In a multicenter retrospective cohort study from China by Wu et al, increased D-dimer levels (>1 μg/mL) were significantly associated with in-hospital death in the multivariable analysis [15]. Similarly, the same study also showed that higher serum ferritin was associated with ARDS development. Zhou et al. also supported an association between higher serum ferritin levels and death [21]. D-dimer was high (>1.0 mg/L) in 58% of our patients and high ferritin levels (>500 ng/ml) were present in 42% patients who had died at our center during the study duration. Follow-up D-dimer estimation in 14 patients showed increased levels. Thus, we conclude that the D-dimer dynamics can reflect the severity of disease and their increased levels are associated with adverse outcomes among patients with COVID-19.

Our study has some limitations. Since this was a single centered study, the results cannot be generalized. Secondly, being a retrospective study, laboratory tests of all the patients were not available, including quantitative CRP measurements, D-dimer and serum ferritin levels. Therefore, their role might have been underestimated in predicting the inhospital deaths. Thirdly, some patients were transferred late in their illness to our hospital. Lack of early interventions and inadequate adherence to standard supportive therapy, might have also contributed to the poor clinical outcome in some patients. Fourthly, a significant number of critical patients were referred to centers due to multiple reasons. Follow up and outcome of those patients were not included in this study. Furthermore, data related to thromboembolism, which is a significant cause of COVID-19 related death, could not be investigated due to logistic limitation.
