Background: Transgenderism has always been part of society, with some individuals experiencing gender dysphoria (GD). When present, it is associated with diminished quality of life (QoL), along with minority stress, compared to the cisgender population.

Aim: The primary objective of this study was the validation of the Essen Transgender Quality of Life-Inventory (ETLI), originally designed for assigned male at birth (AMAB) transgender individuals, in the German population on those assigned female at birth (AFAB).

Methods: A multi-center survey study with 139 participants was conducted. The assessment encompassed sociodemographic and medical data, and the following instruments: ETLI (transgender-specific QoL), F-SozU (social support), PHQ-8 (depression), GAD-7 (anxiety), and the Belief in a Just World questionnaire. Visual analogue scales (VAS) assessed physical and mental health, general QoL, and social environment quality. Following the Strengthening the Reporting of Observational Studies in Epidemiology guidelines, descriptive statistics, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), reliability analysis, and intercorrelation analysis of ETLI subscales were performed, along with bivariate correlations with related instruments proximal and distal to the questionnaire to assess construct and criterion validity.

Outcomes: Outcomes included factor structure, reliability, as well as construct and criterion validity of the ETLI.

Results: The initial CFA, based on previous work, indicated a suboptimal factor structure, leading to the conduction of an EFA, which suggested a revised factor model. A subsequent CFA confirmed a satisfactory model fit for the proposed structure. All ETLI scales reached high reliability coefficients. Intercorrelation analysis revealed moderate to high associations among subscales. Convergent validity was confirmed by significant correlations of ETLI subscales with the PHQ-8, GAD-7, and F-SozU questionnaires. Discriminant validity was partially supported through the Belief in a Just World questionnaire. Criterion validity was affirmed using the VAS regarding general QoL, mental and physical health, and social environment quality.

Clinical implications: Due to its confirmed validity and reliability as well as the lack of viable alternatives, the ETLI provides healthcare professionals with a robust tool to assess QoL issues specific to this population, facilitating more targeted and effective interventions to improve QoL.

Strengths and limitations: Strengths are the inclusion of a heterogeneous age range and the use of advanced statistical analyses. However, recruitment from specific clinics and a limited sample size restrict the generalizability of our study.

Conclusion: The study substantiates the ETLI's construct and criterion validity among the AFAB demographic, demonstrating satisfactory reliability and confirming the revised factor structure through a subsequent CFA.