Fig 3.

Classification algorithm for 1p/19q-codeletion status in IDH-mutant LGGs, derived from an analysis of the TCGA/TCIA training cohort. The first step of the algorithm is an assessment of the T2-FLAIR mismatch sign; when present, it indicates, with high certainty, the IDH-mutant 1p/19q-noncodeleted subtype. When the T2-FLAIR mismatch sign is absent (or unavailable), a multivariate logistic regression model based on tumor texture, patient age, T2* blooming, tumor location, and hydrocephalus is applied. The equation for the logistic regression model is the following: ρ codeleted = exp[(Xβ) / (1+exp(Xβ)′], where Xβ = −4.8834 + 2.7842 × (texture <75% homogeneous) + 0.0587 × (patient age) + 3.1948 × (T2* susceptibility blooming present) + 1.6646 × (primary lobe = frontal) − 3.4496 × (hydrocephalus = present). A predicted probability threshold of 0.40 was established for the logistic regression model, based on the Youden J statistic. Cases were classified as either 1p/19q codeleted or non-codeleted based on whether their predicted probability was ≥ or < 0.40, respectively.