Lymphopenia and IgG2 subclass deficiency in patients with severe COVID-19 pneumonia

COVID-19 caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) manifests with a range of disease severities. A small proportion of COVID-19 patients are severely ill; however, a significant proportion of these patients are critically ill, and require admission and mechanical ventilation, which is associated with a high mortality.

To identify factors that may predispose patients with COVID-19 to severe disease that requires mechanical ventilation (MV).

We performed a retrospective audit of patients admitted with COVID-19 pneumonia to the intensive care unit (ICU) and medical wards to evaluate the potential associations between comorbid conditions, lymphopenia and IgG subclass deficiency with a need for MV.

A total of 51 patients were included in the study. Almost half of the patients (47%; n=24) were documented to have IgG2 deficiency, 43% (n=22) had lymphopenia and 37% (n=19) had combined lymphopenia and IgG2 subclass deficiency. Of the 24 patients who required MV, 75% had IgG2 subclass deficiency, 73% had lymphopenia and 50% had both. The relative risk for requiring MV was 2.64, 3.38 and 2.81 for lymphopenia, IgG2 subclass deficiency and both, respectively.

These findings suggest that lymphopenia, low IgG2 concentrations or the combination of both may be used to identify patients with severe COVID-19 that are at increased risk for MV. This may facilitate earlier identification of patients at high risk, who may benefit from more intensive therapy.