The laboratory findings and different COVID-19 severities: a systematic review and meta-analysis

Ann Clin Microbiol Antimicrob. 2021 Mar 16;20(1):17. doi: 10.1186/s12941-021-00420-3.


Background: Abnormal laboratory findings are common in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The aim of this systematic review was to investigate the effect of the level of some laboratory factors (C-reactive protein (CRP), creatinine, leukocyte count, hemoglobin, and platelet count) on the severity and outcome of coronavirus disease 2019 (COVID-19).

Methods: We searched PubMed, Web of Science, Scopus, and Google Scholar. We collected the articles published before May 26, 2020. We gathered the laboratory factors in groups of patients with COVID-19, and studied the relation between level of these factors with severity and outcome of the disease.

Results: Mean CRP level, creatinine, hemoglobin, and the leukocytes count in the critically ill patients were significantly higher than those of the other groups (non-critical patients); mean CRP = 54.81 mg/l, mean creatinine = 86.82 μmol/l, mean hemoglobin = 144.05 g/l, and mean leukocyte count = 7.41 × 109. The lymphocyte count was higher in patients with mild/moderate disease (mean: 1.32 × 109) and in the invasive ventilation group (mean value of 0.72 × 109), but it was considerably lower than those of the other two groups. The results showed that the platelet count was higher in critically ill patients (mean value of 205.96 × 109). However, the amount was lower in the invasive ventilation group compared with the other groups (mean level = 185.67 × 109).

Conclusion: With increasing disease severity, the leukocyte count and the level of CRP increase significantly and the lymphocyte count decreases. There seems to be a significant relation between platelet level, hemoglobin, and creatinine level with severity of the disease. However, more studies are required to confirm this.

Keywords: C-reactive protein; COVID-19; Creatinine; Hemoglobin; Leukocyte; Lymphocyte; Platelet.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • C-Reactive Protein / analysis
  • COVID-19 / blood*
  • Creatinine / blood
  • Hemoglobins / analysis
  • Humans
  • Laboratories
  • Leukocyte Count
  • Platelet Count
  • SARS-CoV-2*
  • Severity of Illness Index*


  • Hemoglobins
  • C-Reactive Protein
  • Creatinine