Platelet-to-lymphocyte ratio (PLR), a novel biomarker to predict the severity of COVID-19 patients: a systematic review and meta-analysis

Abstract

Background Platelet-to-lymphocyte ratio (PLR), a novel inflammatory marker, has been suggested to be able to predict the severity of COVID-19 patients. This systematic review aims to evaluate the association between PLR levels on admission and the severity of COVID-19 patients. Methods A systematic literature search was done on 23 July 2020 to identify peer-reviewed studies across four different databases (Ovid MEDLINE, EMBASE, SCOPUS, and the Cochrane Library), preprints from two databases (MedRxiv and SSRN), and grey literature from two databases (WHO COVID-19 Global Research Database and Center for Disease Control and Prevention COVID-19 Research Article). Research articles comparing the PLR value on admission in adult patients with COVID-19 with varying degrees of severity were included in the analysis. The following keywords were used for the search: 'COVID-19', 'PLR', 'severity', and 'mortality'. The inverse variance method was used to calculate the pooled effect standardized mean difference (SMD) along with its 95% confidence interval (CI). Results A total of seven studies were included in the meta-analysis, six of which were conducted in China. From a total of 998 participants included, 316 (31.7%) had severe diseases; and those in the severe group were generally older and had underlying diseases compared to the non-severe group. In comparison to non-severe patients, the meta-analysis showed that severe COVID-19 patients had higher PLR levels on admission (SMD 0.68; 95%CI 0.43-0.93; I2 =58%). Conclusion High PLR levels on admission were associated with severe COVID-19 cases. Therefore, on-admission PLR level is a novel, cost-effective, and readily available biomarker with a promising prognostic role for determining the severity of COVID-19 patients.

Platelet Indices and Platelet to Lymphocyte Ratio (PLR) as Markers for Predicting COVID-19 Infection Severity

“…The findings of the present study were similar to the study done by Simadibrata DM et al, which showed that the patients with severe COVID-19 illness had higher PLR levels on admission (SMD 0.68; 95%CI 0.43-0.93; I2 =58%) [7].…”

Prognostic biomarkers in COVID-19 infection: value of anemia, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and D-dimer

“…Platelet-to-lymphocyte ratio is another simple costeffective but less commonly used method that is calculated from CBC and could be of a value in predicting COVID-19 severity. Two recent meta-analysis evaluating PLR value in COVID-19 infection showed that cases with severe COVID-19 had higher admission levels of PLR [29,30]. Moreover, the number and the dynamic fluctuations of the platelets during the management may provide an idea on the prognosis and severity of the illness.…”

Neutrophil-to-lymphocyte Ratio and Platelet-to-lymphocyte Ratio, Novel Biomarkers and Applications in Urology: An Update

“…Upsurge in the PLR meter recommend an overactive inflammatory reaction and worsen prognosis. Additionally, PLR is sensitive towards natural as well as acquired immune reactions [3,8,9]. The normal range of the PLR is varied and based on several clinical research.…”