Association of MDR1 gene C3435T polymorphism with childhood intractable epilepsy: a meta-analysis

Drug-resistant epilepsy is also referred to as intractable, medically refractory, or pharmacoresistant epilepsy. Approximately, one-third of patients with epilepsy have recurrent seizures despite therapy. Multidrug resistance 1 (MDR1) gene may play a role in drug-resistance in epilepsy. To assess the association between MDR1 C3435T polymorphism and the response to anticonvulsants in childhood intractable epilepsy, we conducted a systematic review and meta-analysis. Studies were obtained from the electronic database of PubMed, Medline, Embase and CNKI up to September 2013. All the case-control association researches evaluating the role of MDR1 C3435T polymorphism in childhood epilepsy to antiepileptic drugs were identified. The odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for comparisons of the alleles and genotypes with co-dominant (C/C vs. T/T, C/T vs. T/T), dominant (C/C + C/T vs. T/T), and recessive (C/C vs. C/T + T/T) models in overall and in ethnicity subgroups to measure the strength of genetic association. A total of 8 related studies, including 634 drug-resistant patients, 615 drug-responsive patients and 1,052 healthy controls were pooled in this meta-analysis. The allelic association of MDR1 C3435T with risk of drug-resistance was not significant (OR 1.03, 95% CI 0.87-1.22, P = 0.73; OR 1.00, 95% CI 0.86-1.16, P = 0.98) in overall and in the subgroup analysis by ethnicity (Asian: OR 0.95, 95% CI 0.77-1.18, P = 0.67; Caucasian: OR 1.18, 95% CI 0.89-1.57, P = 0.25). Neither association was found in other genetic models. Our results did not show a significant association between MDR1 C3435T polymorphism and response to anticonvulsant drugs, suggesting that this polymorphism may not be a risk factor to childhood intractable epilepsy.