C9orf72 hexanucleotide repeat in Huntington-like patients: Systematic review and meta-analysis

The protocol was registered on the International Prospective Register of Systematic Reviews database (PROSPERO) (registration number: CRD42018105465). The search was carried out in Medline, Scopus, Web of Science, and Embase in April 2018. Observational studies reporting patients with HLD carrying the hexanucleotide repeat expansion in the <i>C9orf72</i> gene were selected and revised; this process was carried out in duplicate. The cutoff threshold for considering the hexanucleotide expansion as a pathogenic variant was equal or more than 30 G₄C₂ repeats. The pooled frequency and 95% CI were calculated with random effect models.