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

Abstract

Platelet-to-lymphocyte ratio (PLR), a novel inflammatory marker, has been suggested 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. A systematic literature search was done on 23 July 2020 to identify peer-reviewed studies, preprints, and grey literatures. 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”. 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%). High PLR levels on admission were associated with severe COVID-19 cases. Therefore, the 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.

A Study on Factors Impacting Length of Hospital Stay of COVID-19 Inpatients

“…[20] As for cause-specific survival analysis, we have found even more factors to be associated with the rate of mortality or rate of discharge of a COVID-19 patient. Almost all factors we measured are associated with the rate of event (Table 2, [21][22][23][24][25][26][27][28][29][30][31][32][33][34] The fact that every single one of the factors we found to be significantly associated with rate of mortality/ discharge in Tables 2 and 3 had also been discussed in the literature, not only confirm our findings, but also show an extensive dysregulation in COVID-19 patients. Outpatients, with their zero hospitalization stay time, do not contribute to my analysis concerning stay time.…”

Evaluation of hematological parameters as an indicator of disease severity in Covid‐19 patients: Pakistan's experience

“…Thus, supporting the evidence of platelet-to-lymphocyte ratio as one of the independent mediator predicting mortality and prognosis in critically ill sufferers synchronizing with the results of another study. 26,27 The means of platelet-to-lymphocyte ratio detected among patients under treatment in the isolation ward and intensive care units coincide with the means of the study mentioned above Moreover, As noted by Xu et al, 28 in acute ischemic stroke patients who are treated with intravenous thrombolysis, elevated PLR levels seem to be independently associated with an unfavorable outcome and death after three months. PLR is also identified as a diagnostic tool in inflammatory bowel syndrome.…”

COVID-19 outpatients and surviving inpatients exhibit comparable blood test results that are distinct from non-surviving inpatients

“…In addition to CRP and HGB, calcium, potassium, sodium, WBC, neutrophil, lymphocyte cell count and Vitamin-D are extensively discussed in the literature (38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50). All of these factors except Vitamin D and potassium show significant differences between non-surviving and surviving patients in Table 3 and are discussed in the literature, which confirm our findings and indicate dysregulation in COVID-19 patients.…”