Sex of participants are inferred during the automated genotype calling process in AxAS based on X and Y linked variants. Samples failing this inference are flagged as “unknown” sex. This can reflect underlying sex-chromosome aneuploidy and mosaicism. Such conditions can be identified after conducting a Copy Number Variant (CNV) analysis using the AxAS. The probeset intensities across whole sex chromosomes of “unknown” sex samples are visualised and compared to those of male or female references (7). Samples with an “unknown” sex that remain unresolved or presenting sex-chromosome aneuploidy will be flagged and removed. Additionally, samples showing a discrepancy between the self- reported sex in questionnaire at recruitment and the genetically inferred sex are also removed as indicative of potential sample mix-ups.