Regional differences in the frequency of the c. 985A>G ACADM mutation: findings from a meta-regression of genotyping and screening studies.

Several countries include medium-chain acyl- CoA dehydrogenase ( MCAD) deficiency, a rare autosomal recessive disease, in their newborn screening programmes despite prevalence uncertainty. We estimated the frequency of its most common mutation, c. 985A>G, tested for regional differences and compared screening and genotype frequencies. We identified 43 studies reporting the frequency of c. 985A>G over 10 million individuals, and pooled frequency data using a novel Bayesian approach. We found significant variation in the frequency of the mutation across regions supporting a reported founder effect. The proportion of c. 985A>G homozygotes was highest in Western Europe with 4.1 (95% CI: 2.8-5.6) per 100,000 individuals, then the New World (3.2, 95% CI: 2.0-4.7), Southern (1.2, 95% CI: 0.6-2.0) and Eastern European regions (0.9, 95% CI: 0.5-1.7). No cases with the mutation were identified in Asian and Middle Eastern regions. Significant differences were found in some countries between the genotype and screening allele frequency of c. 985A>G. Our predictions could inform the frequency of the mutation by region and our approach could apply to other genetic conditions. [ABSTRACT FROM AUTHOR]