Predictors of severity in COVID-19

Abstract

Background: In the context of home monitoring of severe acute respiratory syndrome coronavirus-2 disease (COVID-19) patients, it is imperative to evaluate the accuracy of finger pulse oximetry oxygen saturation (SpO2) in the assessment of hypoxia. Methods: Retrospective data analysis was performed on (n = 132) hospitalised COVID-19 patients with various levels of severity, in whom SpO2, haematological, biochemical and arterial blood gas (ABG) parameters were measured within 48 h after admission. Discrepancy between SpO2 and arterial blood oxygen saturation SaO2 was compared between mild, moderate and severe COVID-19 to assess the accuracy of finger pulse oximetry. Results: We found that total white blood cell count, neutrophil %, neutrophil–lymphocyte ratio, platelet–lymphocyte ratio, ferritin, C-reactive protein and lactate dehydrogenase (LDH) were significantly increased in severe COVID-19, while lymphocyte % was significantly less when compared to mild and moderate cases. Multivariable analysis suggested that red cell distribution width (RDW) and LDH together account for significant variance in the severity of disease. The SpO2 and SaO2 were significantly less in the severe group. The difference between SpO2 and SaO2 has a clinically meaningful albeit statistically nonsignificant trend with the discrepancy greater in severe COVID-19 cases when compared to mild and moderate cases. Conclusions: Finger pulse oximetry has the potential to underestimate the severity of hypoxia in severe COVID-19 and this has implications in the decision to start oxygen therapy. RDW and LDH constitute the best parsimonious set of variables to predict severity.

Keywords

• arterial blood gas analysis
• covid-19
• finger pulse oximetry
• hypoxia