Study characteristics
Figure 1 summarises the number of studies screened and selected. Fifty studies with 18,449 participants were included: 29 randomised trials (58%), seven non-randomised controlled trials (14%), seven consecutive case series (14%) and seven case-control studies (14%). Three studies focused on diagnosis, 26 on the acute management of anaphylaxis or the characteristics of adrenaline administration, 9 on education to improve emergency management and 12 on long-term management and prevention.
Overall, 50% of the studies were from North America, 28% from Europe, 12% from Asia, 4% from Australia and 6% from elsewhere. Two thirds (66%) of the studies were published between 2010 and 2020, 18% from 2000 to 2009 and 16% prior to 2000. The online supplement summarises the individual studies and their risk of bias assessments (see supplement S3).
More than half of the studies (56%) were at high risk of bias, 40% at moderate risk and 4% at low risk. The GRADE certainty of evidence was generally low or very low (online supplements S4-8) and was often downgraded due to risk of bias, indirectness and imprecision.
The studies contained multiple outcomes, measured in a range of ways and at a variety of time points. Space does not permit a description of every outcome so only a selection are described here and not all numerical findings and confidence intervals are listed. The online supplements describe the outcomes in more detail.