The baseline risk of multiple febrile seizures in the same febrile illness: a meta-analysis

The baseline risk for multiple febrile seizures within the same febrile illness is largely unknown. Estimates range from 5 to 30%. Imprecise estimates can lead to incorrectly powering studies investigating the management of febrile seizures. To estimate the risk of multiple febrile seizures in the same febrile illness, we systematically reviewed and conducted a meta-analysis of studies from January 2000 to December 2021 that contained data for the number of children for both simple and complex febrile seizures in the same febrile illness. We searched MEDLINE, EMBASE, and Web of Science for randomized, quasi-randomized, prospective, and retrospective trials that involved children with febrile seizures. A total of 23,131 febrile illnesses with febrile seizures met the inclusion criteria. The estimated baseline risk of multiple febrile seizures in the same febrile illness was 17% (95% CI, 16-19%). However, the 30 cohorts that included both admitted and non-admitted patients had a lower percentage of multiple FSs within the same illness (14%; 95% CI, 12-15%) than the 30 cohorts that enrolled only admitted patients (20%; 95% CI, 16-25%).

Researchers can use estimates in this paper to design future studies. Taking into the account the substantial heterogeneity between countries and studies, clinicians could cautiously use our estimates in their clinical assessment and be better able to set parental expectations about a child's chances of having another febrile seizure during the current illness.

PROSPERO CRD42020191784. Registered July 18, 2020.

• There is renewed interest in the diagnostic workup and prophylactic treatment of febrile seizures to prevent repeat seizures in the same febrile illness. • There is a lack of accurate estimates of the baseline risk for multiple febrile seizures in the same illness to properly design studies investigating management.

• This study provides the most robust estimates for the baseline risk for multiple febrile seizures in the same illness.