A Prospective Cohort Study Of The Incidence And Risk Factors Of Recurrent Febrile Seizures And Epilepsy Following Febrile Seizures

This was a single-center, longitudinal cohort study. Vietnamese children were prospectively identified for their first febrile seizures (FS) through the General Pediatric Department and Neurology Department of Children's Hospital 2 in Ho Chi Minh City between March and December 2023. This hospital is one of the largest tertiary pediatric hospitals in southern Vietnam with 1,400 beds, and receives about 90,000 admissions every year, with 800-1,000 cases of initial FS. After recruitment, the participants have been monitored for an average of two years to determine whether they experience recurring FS or develop epilepsy.

Sample size and sampling:

The sample size was calculated using a specific formula to estimate the incidence of FS recurrence in the cohort study. With the desired confidence level of 95%, an estimated error of 0.1, and an expected incidence of 31.8% based on a similar study conducted by Berg, the minimum sample size required was determined to be 385 participants. The sample size was also estimated based on the number of events per predictor in regression models, with at least 10 events per predictor recommended by Peduzzi et al. For the recurrent FS outcome, we have 12 potential predictor variables including age of onset, male gender, prematurity, low birth weight, neurodevelopmental abnormality, family history of FS or epilepsy, temperature, duration of fever at the time of the seizure, and characteristic of the first FS such as semiology, duration and number of seizures during the illness yielding approximately 120 cases to achieve the required sample size for estimating recurrence of FS. Besides that, we also have 16 potential predictor variables for the subsequent epilepsy outcome, including the above factors adding to the number of FS, and characteristics of all FS (first and recurrences). As such, we aimed to obtain at least 160 children. Finally, the overall sample size required at least 385 patients.

Convenience sampling was applied to recruit the participants. In detail, every weekday, the list of inpatient reports of the General Pediatric Department and Neurology Department on the electronic medical record database of Children's Hospital 2 was used to identify all children who had been diagnosed with FS and admitted to these departments. The investigator met with these children's parents or caregivers and asked a series of screening questions to confirm that they had not previously experienced febrile or unprovoked seizures. If the child had such a history, they were excluded from the study. The patients were then followed up until they recovered and were discharged from the hospital. At this point, the investigator made the final diagnosis of the first FS and assessed whether any exclusion criteria applied. If the patients were eligible for the study, the investigator obtained informed consent from their parents and proceeded to gather study data.

Data collection