Platelet size as a predictor for severity and mortality in COVID-19 patients: a systematic review and meta-analysis

ABSTRACT Background Parameters reflecting platelet size can be sensitive indicators that circulating platelets are activated and COVID-19 patients are at increased risk of thrombosis. This systematic review aims to assess the association of mean platelet volume (MPV), platelet distribution width (PDW) and platelet-large cell ratio (P-LCR) with disease severity and mortality in COVID-19 patients. Methods English and Chinese databases were searched electronically to identify studies reporting data on MPV, PDW or P-LCR in COVID-19 patients. Included articles underwent a quality rating. A meta-analysis was performed using the standard mean difference and interpreted as the common language effect size (CLES). Results Twenty-two studies (11,906 patients) were included in the meta-analysis. Of these, 14 were rated poor and eight were fair. The MPV and P-LCR was significantly higher at hospital admission in severe patients compared to non-severe patients. The MPV, PDW and P-LCR were significantly higher at hospital admission in non-survivors compared to survivors. There was a marked increase in the probability of a severe COVID-19 patient presenting with higher P-LCR at hospital admission than a non-severe patient (CLES: 68.7% [95% CI: 59.8%, 76.5%]), when compared with MPV and PDW ((CLES: 59.2% [95% CI: 53.1%, 65.1%]) and (CLES: 55.9% [95% CI: 50.6%, 62.2%]), respectively). Conclusion Severe COVID-19 disease is associated with the increased production of larger, younger platelets. When comparing MPV, PDW and P-LCR, P-LCR is the most important biomarker for evaluating platelet activity. P-LCR testing at hospital admission could identify COVID-19 patients with increased risk for thrombotic events, allowing preventative treatment. Summary Table What is known on this topic The incidence of thrombotic complications is high in COVID-19 patients with severe disease. Parameters reflecting platelet size can be sensitive indicators that circulating platelets are activated and that COVID-19 patients are at increased risk of thrombosis. What does this paper add When compared to MPV and PDW, P-LCR is the most important biomarker for evaluating platelet activity in COVID-19 patients at hospital admission and could be used to identify patients with increased risk for thrombotic events. Current evidence is predominantly derived from retrospective design. Prospective studies are warranted to accurately determine cut-off values that may be used in the clinical setting.