Summary of findings 3.
Summary of findings ‐ Time to first seizure after randomisation
| Carbamazepine compared with phenytoin for epilepsy | ||||||
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Patient or population: adults and children with new‐onset partial or generalised epilepsy Settings: outpatients Intervention: carbamazepine Comparison: phenytoin | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI)1 | No of Participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Phenytoin | Carbamazepine | |||||
| Time to first seizure ‐ stratified by epilepsy type Range of follow‐up (all participants): 0 days to 4589 days |
65 per 100 | 71 per 100 (63 to 77) | HR 0.85 (0.70 to 1.04) |
582 (4 studies) |
⊕⊕⊝⊝ low2,3,4 |
HR > 1 indicates a clinical advantage for carbamazepine |
| Time to first seizure ‐ partial epilepsy Range of follow‐up (all participants): 0 days to 4589 days |
63 per 100 | 68 per 100 (60 to 77) | HR 0.86 (0.68 to 1.08) |
432 (4 studies) |
⊕⊕⊝⊝ low2,3,4 |
HR > 1 indicates a clinical advantage for carbamazepine |
| Time to first seizure ‐ generalised epilepsy Range of follow‐up (all participants): 2 days to 4070 days |
69 per 100 | 75 per 100 (61 to 87) | HR 0.84 (0.57 to 1.24) |
150 (3 studies) |
⊕⊕⊝⊝ low2,3,4 |
HR > 1 indicates a clinical advantage for carbamazepine |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The assumed risk is calculated as the event rate in the Phenytoin treatment group The corresponding risk in the carbamazepine treatment group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). The corresponding risk is calculated as the assumed risk x the relative risk (RR) of the intervention where RR = (1 ‐ exp(HR x ln(1 ‐ assumed risk)) ) / assumed risk CI: Confidence interval; HR: Hazard Ratio; exp: exponential | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
1Pooled HR for all participants adjusted for seizure type.
2Risk of bias unclear for one element of all of the three studies included in the analysis. De Silva 1996 and Heller 1995 are open‐label and it is unclear whether the lack of masking impacted upon the results; and we do not know how allocation was concealed in Mattson 1985.
348 adult participants in Heller 1995 and Ogunrin 2005 may have had their seizure type wrongly classified as generalised onset; sensitivity analyses show misclassification is unlikely to have had an impact on results and conclusions.
4Ogunrin 2005 is a short study (12 weeks) and has a small sample size of 37 compared to the other three studies of duration 3 ‐ 10 years and sample sizes of around 100 to 300 participants (De Silva 1996; Heller 1995; Mattson 1985). Ogunrin 2005 is less precise with wide CIs, and there is evidence that the treatment effect in this study changes over time.