Sex estimation from the mastoid process using Micro-CT among Brazilians: Discriminant analysis and ROC curve analysis

The present study aimed to analyze morphometric variables of the mastoid process using X-ray microtomography images for sex estimation. The sample was composed of 60 microtomography images from dried skulls. Three measurements were applied: asterion-porion, mastoideale-porion and asterion-mastoideale. The area of the triangle was calculated by two methodologies: software myVGL2.2 + Heron's formula (M1) and software myVGL2.2 + Adobe Photoshop CS6 (M2). The right area (RA) and left area (LA) were calculated, and the sum of them was considered the total area (TA). Descriptive analysis of M1 and M2 showed statistically significant differences between sex (p < 0.05). The univariate discriminant analysis showed an overall percentage of correct classification of sex varying between 75-80% for M1 and 71.7-73.3% for M2. The multivariate discriminant analysis demonstrated reduced classification percentages. The ROC curve analysis showed better results for M1 compared to M2. The best variable using M1 was the TA, with an 81.45% accurate sex estimation. Based on the ROC curve analysis results, a reference table was developed to be applied for the sex estimation of Brazilian individuals. In conclusion, the mastoid process has good sexual dimorphism in Brazilian skulls and can be considered a tool for predicting sex in cases of fragmented craniums.