Allergen Immunotherapy for asthma prevention: a systematic review and meta-analysis of randomised and non-randomised controlled studies.

BACKGROUND:

Allergen immunotherapy (AIT) is a disease-modifying treatment for IgE-mediated diseases. Randomised controlled trials (RCTs) support AIT's potential role in asthma prevention but evidence from non-randomised studies of interventions (NRSI) and longitudinal observational studies has been poorly addressed. Therefore, we aimed to conduct a systematic review and meta-analysis to assess clinical data from all study types to evaluate quantitatively the preventive role of AIT in asthma onset.

METHODS:

We search three databases. Studies were screened, selected, and evaluated for quality using risk-of-bias (ROB) tools. Data were descriptively summarized and meta-analysed using random-effects. We performed a sensitivity, influence, and subgroup analyses. Publication bias and heterogeneity were assessed.

RESULTS:

From the 4549 identified studies, 24 (12 RCTs, 12 NRSI) were included in the qualitative synthesis and 18 underwent meta-analysis. One study was at low ROB, seven had moderate ROB, and 15 were proven of high ROB. Random-effects analysis showed a significant decrease in the risk of developing asthma following AIT by 25% (RR, 95%CI: 0.75, 0.64-0.88). This effect was not significant in the sensitivity analysis. Publication bias raised concerns, together with the moderate heterogeneity between studies (I2=58%). Subgroup analysis showed a remarkable preventive effect of AIT in children (RR, 95%CI: 0.71, 0.53-0.96), when completing three years of therapy (RR, 95%CI: 0.64, 0.47-0.88), and in mono-sensitised patients (RR, 95%CI: 0.49, 0.39-0.61).

CONCLUSIONS:

Our findings support a possible preventive effect of AIT in asthma onset and suggest an enhanced effect when administered in children, mono-sensitised, and for at least three years, independently of allergen type.