CRP and COVID-19: The meta-analysis indicated that the NAC-treated group of COVID-19 patients had significantly lower CRP levels compared with the placebo group [SMD, −0.32; (95% CI: −56 to −0.09); p-value = 0.0070], although the studies have a high degree of heterogeneity (I2 = 88%) (Fig. 2A and Table 2).