Comparing two-step approaches to measuring gender identity: the reliability and applications of asking about sex assigned at birth vs transgender self-identification.

Inclusive measures of gender are critical for health equity research. This study compared the reliability and applications of 2 different approaches for measuring gender in response to emerging community concerns regarding the potential harms of asking about sex assigned at birth (SAAB) within transgender and gender diverse (TGD) populations. Using data from a 2021 survey of LGBTQ+ people in Washington state, we compared approaches for measuring gender via a 2-step question that collected data on (1) current gender and SAAB vs (2) current gender and transgender self-identification. Among 2275 LGBTQ+ participants aged 9-81 years, 63% were cisgender, 35% TGD, and 2% were not categorized. There was near perfect agreement between the 2 methods in their ability to identify TGD participants (percent agreement = 99.7%, unweighted Cohen's Kappa = 0.99). Among gender diverse participants, stratification by SAAB revealed differences in sexual health outcomes, while stratification by transgender self-identification revealed differences in access to gender-affirming care and lifetime experiences of discrimination. Ascertaining SAAB may be most useful for identifying sexual health disparities, while transgender self-identification may better illuminate healthcare needs and social determinants of health among TGD people. Researchers and public health practitioners should critically consider the acceptability and relevance of SAAB questions to their research goals.