The widespread use of glucocorticoids may not benefit everyone. Severe COVID-19 may be an indication for glucocorticoid treatment only if an uncontrolled inflammatory response occurs. A decrease in lymphocytes may reflect patient immune system impairment and the possibility of progressing to a severe case. Therefore, glucocorticoids may be able to benefit such patients. Our study suggests that patient in-hospital mortality increases as lymphocyte counts decrease, and methylprednisolone treatment improved in-hospital survival for patients with lymphocyte counts less than 0.9*109/L.
COVID-19 is an infectious disease that emerged at the end of 2019. The vast majority of patients with novel coronavirus pneumonia present with only mild to moderate symptoms, and a minority of patients progress to severe pneumonia and even develop ARDS and multiorgan failure [14]. Novel coronavirus infection may induce a protective intrinsic and adaptive immune response in the body, but an excessive intrinsic or impaired adaptive immune response will lead to local and systemic tissue damage[15]. In patients with novel coronavirus pneumonia, the serum levels of several proinflammatory cytokines and chemokines are significantly elevated [16, 17], and high levels of proinflammatory cytokines lead to the development of cytokine storms, as evidenced by massive neutrophil and macrophage infiltration, which lead to diffuse alveolar injury and death from dysfunction of the heart, liver and kidneys. Glucocorticoids can be used to suppress cytokine storms and the intense inflammatory response in lung tissue caused by ARDS, but they may also inhibit host clearance of the virus and thus increase the risk of secondary infection [18]. Therefore, the role of glucocorticoids in novel coronavirus pneumonia is currently controversial.
Chinese experts in respiratory and critical illnesses stated in the "Expert consensus on the use of corticosteroids in patients with 2019-nCoV pneumonia" that glucocorticoids need to be used with caution in patients with novel coronavirus pneumonia [19], and in the WHO guidelines, glucocorticoid therapy is not routinely recommended [20]. However, a recent UK RCT of dexamethasone treatment in hospitalized patients with COVID-19 [8], which included a total of 6,425 patients (2,104 in the dexamethasone treatment group and 4,321 in the control group), yielded positive results. Overall, dexamethasone treatment resulted in a 2.8% reduction in 28-day mortality (22.9% in the dexamethasone treatment group vs. 25.7% in the control group, age-adjusted RR 0.83, 95% CI 0.75–0.93). The greatest benefit was seen for patients receiving invasive mechanical ventilation at randomization, with a mortality rate of 29.3% in the dexamethasone treatment group versus 41.4% in the conventional treatment group (RR 0.64, 95% CI 0.51–0.81). The WHO Rapid Evidence Assessment Working Group also conducted a prospective meta-analysis to determine the prognostic impact of glucocorticoid therapy in critically ill patients with COVID-19 [10], which included data from seven randomized clinical trials with a total of 1,703 critically ill patients; overall, there were 222 deaths in the glucocorticoid treatment group (678 patients) and 425 deaths in the control group (1,025 patients), producing a statistically significant difference in mortality between the two groups (overall OR 0.66, 95% CI 0.53–0.82, p < 0.01 fixed-effects-based meta-analysis). The RCTs [10] in which we found positive findings were mainly conducted in patients with more severe disease, such as those on invasive ventilators, and the mechanism is unclear.
Lymphopenia is a common feature of COVID-19 patients and is the most common prognostic indicator. Reduced peripheral blood lymphocyte counts may be associated with direct viral attack on lymphocytes and lymphoid organs, disorders of inflammatory factors or metabolic disorders such as hyperlactatemia [12]. Lymphocytes express the coronavirus receptor ACE2, which may be a direct target of the virus [21]. Pathological examination of postmortem specimens from COVID-19-infected patients have also showed that SARS-CoV-2 infection can lead to severe tissue damage, including reduced lymphoid follicles, splenic nodule atrophy, histiocytosis and lymphopenia [22, 23]. Our findings also showed that patient in-hospital mortality increased as the lymphocyte count decreased, which is consistent with previous findings. Our Kaplan-Meier survival curve analysis of 624 patients after PS matching showed that methylprednisolone treatment improved in-hospital survival for patients with lymphocyte counts less than 0.9*109/L (P = 0.022), whereas for patients with lymphocyte counts greater than 0.9*109/L, methylprednisolone treatment had no effect on patient in-hospital survival (P = 0.88). Multivariate Cox regression analysis of PS-matched patients with lymphocyte counts less than 0.9*109/L also showed that methylprednisolone treatment reduced patient mortality (P = 0.04). All of these results suggest that glucocorticoid treatment is protective in patients with reduced lymphocyte counts.
The role of glucocorticoids in the treatment of severe viral respiratory infections may depend on the patient, the dose and the timing. Previous studies have shown that dysfunctional monocytes in the peripheral blood of patients with severe novel coronavirus pneumonia lead to sustained activation of the ISG signaling pathway, which may be the main cause of cytokine storm in severe pneumonia [24]. The abnormal immune response is characterized by severe lymphopenia and leukopenia as well as natural killer (NK) cell failure, which lead to a poorer prognosis in some COVID-19 patients [25]. Therefore, in patients with lymphopenia and novel coronavirus pneumonia, glucocorticoid therapy may be protective. Release of SARS-CoV-2 seems to be higher at the beginning of the illness and decreases thereafter [26–29]. High-dose glucocorticoid therapy given specifically when there is minimal inflammation and when viral replication is controlled may cause delayed viral clearance and worse clinical outcomes. The results of a study by D.C. Chen et al. showed a correlation between glucocorticoid treatment at high doses (> 200 mg) and increased early (< 3 days of admission) and 28-day mortality [9]. The results of a clinical trial of dexamethasone [8] have also shown that dexamethasone treatment one week after disease onset reduces mortality in patients with COVID-19, suggesting that immune damage may predominate at this stage of the disease, with active viral replication playing a secondary role.
The present study has some limitations. First, our study was a retrospective analysis, and clarifying the causal relationship between glucocorticoid treatment and mortality was not possible. Second, as this was a retrospective study, the timing, dose and duration of methylprednisolone administration varied, which may lead to biased results. Further prospective large-sample studies are therefore necessary to further confirm the findings.