41 RCTs will be included in this review with no restriction of language, sample size or blinding.
No restrictions were made for language, sample size or period of study, and we included all studies that included children and young people up to age 21.
For HIV and HCV infections, meta-regression demonstrated that these heterogeneities were mainly contributed by the geographical locations of the studies and contributions from study language, sample size, sampling method and study time period were not significant.
In subgroup analysis, the effect size of clinical factors (severity of headache, day of onset, and needle gauge) and the study characteristics (language and sample size) did not differ between groups.
There are 93 studies in Chinese language and 141 studies in English language with the sample size of control group more than 100.
Given the two participant groups for interviews differed by language only, this sample size was determined to be reasonable to meet study objectives [16, 21, 23], and to reach saturation for qualitative assessment [24].
The inclusion criteria were broad so that it would be possible to include all evidence now existing, regardless of the study language, study quality, sample size and other factors.
Three trials, all published in English language journals, reported sample size calculation.
The data were extracted from each included study by two independent investigators, and the following information was collected: surname and initials of the first author, year of submission, country, ethnicity, language, age, gender, sample size, genotyping methods, study design, Hardy-Weinberg equilibrium test (HWE), SNP, and gene.
Despite the large variability in language outcomes, a moderate sample size, and multiple factors that influence these outcomes, significantly faster rates of vocabulary and language development were found for the children with bilateral CIs in this study.
We excluded the group of students with high language proficiency as the sample size was very small (3 %).
