Objective: COVID-19 pandemic has caused numerous deaths. Studies have shown that Krebs von den Lungen-6 (KL-6) levels are associated with severe disease. KL-6 is mainly expressed on type II alveolar epithelial cell surface and respiratory bronchiolar epithelium and is a good indicator of alveolar epithelial cell damage. The purpose of this meta-analysis is to evaluate the association of serum KL-6 levels with COVID19 and other viral infections.

Method: A systematic literature search was conducted with the keywords “Krebs von den Lungen-6” OR “KL-6” AND “virus” OR “viral infections” OR “COVID-19” in PubMed, Web of Science and Scopus. A total of 229 studies were screened, of which 6 were eligible for cumulative meta-analysis.

Results: According to the cumulative meta-analysis results, serum KL-6 levels were significantly higher in the patient groups than in the controls (mean difference: 53.36, 95% CI [27.92, 78.80], p<0.0001). Cumulative ROC analysis results showed that the cut-off value of KL-6 level in viral infections was 262.85 U/mL with 92.3% specificity and 52.2% sensitivity (AUC: 0.920, p<0.001). Data showed, serum KL-6 level was shown to be inversely proportional to both CD8 lymphocyte count and NK cell count (p: 0.0262, r: -0.9738 (n=4); p: 0.0066, r: -0.9934, respectively. (n=4)).

Conclusion:Our results showed that patients with viral infection had higher serum KL-6 levels than controls. However, due to the limited number of studies that can be included and the lack of data in the studies, more studies are needed to understand the relationship between serum KL-6 level and viral infections.

Keywords: COVID-19, krebs von den lungen-6, meta-analysis, SARS-CoV-2, viral infection