IL6 and asthma: Considering the asthma status ( asthma exacerbation/ stable asthma), the results of subgroup analysis of asthma exacerbation showed that serum IL-6 levels were significantly higher in patients with asthma exacerbation than in healthy non-asthmatic controls, with a pooled SMD of 2.15 (95% CI 1.79–2.52, P < 0.00001)[18, 28] (Fig. 5).