Association of serum C-reactive protein (CRP) and D-dimer concentration on the severity of COVID-19 cases with or without diabetes: a systematic review and meta-analysis

Introduction: Coronavirus disease (COVID-19) is a highly contagious disease that poses major public health risks. Fewer studies link high CRP and D-dimer levels to severe COVID-19 infection. Therefore, this study investigates the association of serum CRP and D-dimer concentration with COVID-19 severity in diabetic and non-diabetic patients. Areas covered: Relevant published articles were identified using electronic search engines, such as Google Scholar, PubMed, Springer, Science Direct, and Researchgate. A total of 29 articles reporting on 15,282 patients (4,733 diabetes and 10,549 non-diabetes) were included in this systematic review and meta-analysis. RevMan V5.4, STATA V14 software, and SPSS V25 were used for the meta-analysis. Egger's regression and Begg-Mazumdar's test were used for assessing publication bias. The pooled result of all studies revealed that serum CRP (Standard mean difference (SMD) 0.41 mg/L; P I-2 93%) and D-dimer (SMD 0.32 mg/L; P I-2 83%) concentration was significantly higher in COVID-19 diabetic patients. The prevalence of COVID-19 infection was comparatively higher in male diabetic patients (OR 2.41; P < 0.00001; I-2 88%). There was no publication bias. CRP and D-dimer rose with age in COVID-19 diabetic and non-diabetic patients. Expert opinion: Overall, the serum CRP and D-dimer concentration in COVID-19 diabetic patients was significantly higher than non-diabetic patients indicating severe illness.