Eight RCTs met the inclusion criteria (3,429 participants, range 246 to 576). Six studies were in adults and adolescents (≥12 years) and two were in children (<12 years). All studies met quality assessment criteria for blinding, complete outcome data and selective outcome reporting. Two studies met criteria for random sequence generation. One study met criteria for allocation concealment. Only one study met all five accepted criteria.
Compared to placebo, omalizumab resulted in significantly fewer asthma exacerbations (RR 0.57, 95% CI 0.48 to 0.66, NNTB=10, 95% CI 7 to 13; eight RCTs). There was no evidence of heterogeneity or publication bias and the result was robust across subgroup and sensitivity analyses.
Omalizumab significantly reduced asthma exacerbations per patient (WMD -0.19, 95% CI -0.23 to -0.14; eight RCTs), hospitalisation rates (RR 0.44, 95% CI 0.23 to 0.83; five RCTs), steroid dose (more than 50% dose reduction RR 1.34, 95% CI 1.23 to 1.46; four RCTs) and steroid use (complete withdrawal RR 1.80, 95% CI 1.42 to 2.28; four RCTs). Some heterogeneity was observed, explained by the inclusion of children with mild asthma in one study. There was no difference between omalizumab and placebo in the rate of withdrawal due to adverse events or serious adverse events.
Results for further secondary outcomes were reported.