Thrombocytopenia Is Associated With COVID-19 Severity and Outcome

An Updated Meta-Analysis of 5637 Patients With Multiple Outcomes

Xiaolong Zong, MD; Yajun Gu, PhD; Hongjian Yu, MD; Zhenyu Li, PhD; Yuliang Wang, PhD


Lab Med. 2021;52(1):10-15. 

In This Article

Abstract and Introduction


The COVID-19 pandemic is persistent worldwide. A prior meta-analysis suggested the association of thrombocytopenia (TCP) with more severe COVID-19 illness and high mortality. Considering newly published studies, we updated the previous meta-analysis to confirm and explain the association of TCP with COVID-19 severity and multiple outcomes. Twenty-four studies with 5637 patients with COVID-19 were included in this study. The weighted incidence of TCP in COVID-19 was 12.4% (95% confidence interval [CI], 7.9%–17.7%). Data synthesis showed that the platelet number was lower in patients with either more severe illness or poor outcomes and even lower in nonsurvivors, with weighted mean differences of −24.56 × 109/L, −22.48 × 109/L, and −49.02 × 109/L, respectively. The meta-analysis of binary outcomes (with and without TCP) indicated the association between TCP and 3-fold enhanced risk of a composite outcome of intensive care unit admission, progression to acute respiratory distress syndrome, and mortality (odds ratio [OR], 3.49; 95% CI, 1.57–7.78). Subgroup analysis by endpoint events suggested TCP to be significantly associated with mortality (OR, 7.37; 95% CI, 2.08–26.14). Overall, the present comprehensive meta-analysis indicated that approximately 12% of hospitalized patients with COVID-19 have TCP, which also represents a sign of more severe illness and poor outcomes.


The coronavirus disease 2019 (COVID-19) pandemic has affected more than 12 million people and caused more than 500,000 deaths worldwide.[1] Although most patients develop mild or uncomplicated illness, those with older age and pre-existing comorbidities are more susceptible to severe disease and have a higher risk of poor outcomes such as admission to the intensive care unit (ICU), progression to acute respiratory distress syndrome (ARDS), and even death.[2,3] Thrombocytopenia (TCP) is commonly associated with viral infections and serves as a sign of sepsis progression and exacerbation.[4,5] A prior meta-analysis suggested that low platelet count was associated with high mortality and more severe COVID-19 illness.[6] Because new studies have been published, we conducted an update of the previous meta-analysis to confirm and explain the association of platelet number with COVID-19 severity and provide a direct comparison of the risk of multiple endpoints in patients with COVID-19 with and without TCP.