Linear regression analyses were performed to examine the relationship between AAO, SLC6A4 promoter genotypes and CTQ subtypes as the predictive variables, and the interactions between CTQ subtypes and genotypes was used as the confounding factors. The model was AAO transformed ~ Genotypes(LL versus LS versus SS) + CTQ subtype + Genotypes × CTQ subtype. AAO was reciprocal square root transformed in the French sample and square root transformed in the Brazilian sample to fulfill the normality assumption required by the parametric procedure.
