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

BackgroundParameters 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. MethodsEnglish 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). ResultsTwenty-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). ConclusionSevere 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 TableO_ST_ABSWhat is known on this topicC_ST_ABSO_LIThe incidence of thrombotic complications is high in COVID-19 patients with severe disease. C_LIO_LIParameters reflecting platelet size can be sensitive indicators that circulating platelets are activated and that COVID-19 patients are at increased risk of thrombosis. C_LI What does this paper addO_LIWhen 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. C_LIO_LICurrent 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. C_LI