3.3 Serum IFIH1 levels
IFIH1 levels (median and IQR) were significantly higher in the serum of COVID-19 patients than in HC (15.35 [13.28-17.30] vs . 4.60 [3.17-6.50] ng/mL; p < 0.001) (Figure 2A). ROC curve analysis demonstrated the potential of IFIH1 in distinguishing between COVID-19 patients and HC as indicated by an AUC of 0.999 (95% CI = 0.999-1.0; p < 0.001). At a cut-off point of 10 ng/mL, the sensitivity and specificity of IFIH1 were 100.0 and 97.8%, respectively (Figure 2B).
To evaluate the impact of IFIH1 SNPs on IFIH1 serum levels, these levels were stratified by genotypes of SNPs rs1990760 and rs2111485 in all participating individuals (COVID-19 plus HC patients; n=180). Individuals with the mutant-type genotypes rs1990760 TT (14.2 [8.2-16.9] vs . 3.4 [2.5-4.8] ng/mL; p < 0.001) and rs2111485 GG (13.4 [7.4-16.4] vs . 6.4 [3.4-8.1] ng/mL; p < 0.001) showed significantly elevated levels of IFIH1 compared to the wild-type genotypes (rs1990760 CC and rs2111485 AA, respectively) (Figure 3). Of note, the mutated genotypes rs1990760 TT and rs2111485 GG were significantly associated with an increased risk of infection with COVID-19 (Table 3).