Redefining the gender identity spectrum in longitudinal studies: adolescent response patterns after adopting the two-step measure of sex and gender.

Ongoing, large-scale longitudinal studies and surveillance systems are moving beyond historical single-item sex or gender measures to better capture gender identity. We examined patterns in adolescents' responses over a two-year period (2020-2021 to 2021-2022 school years) after the COMPASS study adopted a two-step measure of gender identity. Descriptive analyses revealed that, over time, 3.5% and 5.5% of high school students (n = 11 618) selected a different response for sex and gender, respectively. Our findings show that by implementing an inclusive measure that recognizes sex and gender as distinct constructs can improve the identification of all gender identities without compromising data quality.