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

Materials and Methods

This systematic review was performed following the PRISMA statement (see Supplemental Material 1).[7] The study protocol is provided in Supplemental Material 2. Briefly, PubMed, Embase, and Web of Science were searched to identify studies between December 1, 2019, and March 15, 2020, without language restriction. The following terms were used: "COVID-19" OR "Corona Virus Disease 2019" OR "coronavirus disease-19" OR "severe acute respiratory syndrome coronavirus 2" OR "SARS-COV-2" OR "2019 novel coronavirus" OR "2019-nCoV" OR "new coronavirus pneumonia." Because new articles on COVID-19 are daily published, eligible articles published between March 15, 2020, and April 18, 2020, were also identified via PubMed using the aforementioned terms with AND for the following terms: "platelet" OR "thrombocytopenia" OR "thrombo*" OR "hemato*." Studies were included in this meta-analysis if they met the following criteria: (i) adult population (older than 18), (ii) COVID-19 was confirmed by laboratory testing, (iii) platelet count or TCP frequency was reported, and (iv) English or Chinese full text was available. Studies involving patients with a particular illness or emergency conditions were excluded (eg, cancer and cardiovascular attack). When studies had significant overlapping data, the most comprehensive study was included.

For pooled analysis, data on platelet count and TCP frequency in the overall population and subgroups based on disease severity or outcomes were extracted by 2 independent investigators. COVID-19 severity was defined as per the World Health Organization or local interim guidance, and studies without definite criteria were excluded. We used a composite of admission to ICU, progression to ARDS, or all-cause mortality to define adverse outcomes of COVID-19. Double-arcsine-transformed proportion, weighted mean difference (WMD), and odds ratio (OR) with 95% confidence interval (CI) were calculated and pooled in the meta-analysis as appropriate. In their absence, the mean and standard deviation of the platelet count were estimated from sample size, median, and interquartile range.[8] A random-effects model was selected to account for clinical heterogeneity. Subgroup analyses were conducted based on endpoint events and TCP definition. The quality of the included studies was evaluated by 2 independent reviewers following the Newcastle-Ottawa scale (see Supplemental Material 3: Table 1). Discrepancies in data extraction and quality assessment were resolved through discussion with a third author. Statistical analyses were performed using the RStudio software.