Platelet count can discriminate between patients with severe and non-severe novel coronavirus disease 2019 (COVID-19) infections.
Patients who did not survive have a significantly lower platelet count than survivors.
Thrombocytopenia is associated with increased risk of severe disease.
A substantial decrease in platelet count should serve as clinical indicator of worsening illness in hospitalized patients with COVID-19.
Coronavirus disease 2019 (COVID-19) is a novel infectious disease with lack of established laboratory markers available to evaluate illness severity. In this study, we investigate whether platelet count could differentiate between COVID-19 patients with or without severe disease. Additionally, we evaluate if thrombocytopenia is associated with severe COVID-19.
An electronic search in Medline, Scopus and Web of Science was performed to identify studies reporting data on platelet count in COVID-19 patients. A meta-analysis was performed, with calculation of weighted mean difference (WMD) of platelet number in COVID-19 patients with or without severe disease and odds ratio (OR) of thrombocytopenia for severe form of COVID-19.
Nine studies with 1779 COVID-19 patients, 399 (22.4%) with severe disease, were included in the meta-analysis. The pooled analysis revealed that platelet count was significantly lower in patients with more severe COVID-19 (WMD -31×10 9/L; 95% CI, from -35 to -29×10 9/L). A subgroup analysis comparing patients by survival, found an even lower platelet count was observed with mortality (WMD, -48×10 9/L; 95% CI, -57 to -39×10 9/L. In the four studies (n=1427) which reported data on rate of thrombocytopenia, a low platelet count was associated with over fivefold enhanced risk of severe COVID-19 (OR, 5.1; 95% CI, 1.8-14.6).