| Methods | Parallel study design, outpatient setting Study conducted in the UK Participants allocated to treatment stratified by age group, gender and seizure type No information provided on method of generation of random list, allocation concealment or blinding |
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| Participants | Participants with 2 or more partial or generalised tonic‐clonic seizure in the past 3 years Participants were previously untreated but started on AED treatment within 3 months of their most recent seizure Number randomised: PHT = 70; SV = 70 63 participants (45%) with partial onset seizures, 73 (52%) men Mean age (range): 35 (14‐70 years). Range of follow‐up: 24‐48 months |
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| Interventions | Monotherapy with PHT or SV Starting doses: PHT 300 mg/day, SV 600 mg/day. Dose achieved not stated |
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| Outcomes | Time to 2‐year remission Time to first seizure Adverse events |
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| Notes | IPD provided for all outcomes included in this review | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Participants randomised with stratification for age group, gender and seizure type. Method of randomisation not stated |
| Allocation concealment (selection bias) | Unclear risk | No information provided |
| Blinding of participants and personnel (performance bias) All outcomes | Unclear risk | No information provided |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No information provided |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Attrition rates reported, ITT approach, all randomised participants analysed from IPD provided (see footnote 2) |
| Selective reporting (reporting bias) | Low risk | All outcomes reported or calculated with IPD provided (see footnote 2) |
| Other bias | Unclear risk | No other bias detected |
1 Abbreviations: AED: antiepileptic drug; IPD: individual participant data; ITT: Intention‐to‐treat; PHT: phenytoin; SV: sodium valproate.
2 For studies which provided IPD, attrition and reporting bias are reduced as attrition rates and unpublished outcome data are requested (Craig 1994; De Silva 1996; Heller 1995; Ramsay 1992; Turnbull 1985).
3 See Figure 2 and Figure 3 for 'Risk of bias' summary and graph.