2.1 Search and inclusion/exclusion criteria
The present systematic review was based on with the PRISMA statement
principles [18]. The PubMed, EMBASE, Cochrane library, Chinese
National Knowledge Infrastructure, Chinese Science and Technique
Journals Database, China Biology medicine disc and Wan Fang Database
were searched up to 30 April 2020 using the boolean combination of the
following key terms: “Carbamazepine” OR “ABCB1 ” OR
“MDR1 ” OR “EPHX1 ” OR “SCN1A ” AND
“polymorphism”. Eligible studies were required to meet the following
inclusion criteria: (i) case–control studies; (ii) investigating the
association of ABCB1 polymorphisms and or EPHX1polymorphisms and plasma concentration or resistance of CBZ in epileptic
patients; (iii) reporting sufficient data for estimating an odds ratio
(OR) for the association with the gene variants of interest; (ⅳ) each
patient was administrated with CBZ monotherapy and not receiving
pharmacological treatment for other pathologies; (ⅴ) including at least
3 studies for each polymorphism to allow calculation of publication bias
between studies.
Exclusion criteria: (i) review articles and editorials; (ii) duplication
of previous publications; (iii) not human studies; (ⅳ) not English or
Chinese articles. All potentially relevant studies retrieved in the
initial screening step were then read in their entirety to assess
appropriateness for inclusion in the systematic review. The reference
lists of all included studies and relevant reviews were also checked to
identify additional studies missed from the initial electronic search.
The corresponding authors were contacted by e-mail when relevant data
could not be extracted from the original paper. Studies were excluded if
the corresponding author did not answer to the e-mail or was unable to
provide the requested data. If two or more studies shared part of the
same patient population, the one with the larger sample size was
included. All studies were independently analysed by two reviewers and
any discrepancies in data extraction were resolved through consensus.