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.