Determining the Sex Assigned at Birth of Transgender and Nonbinary Populations in Administrative Claims Databases Utilizing Diagnostic and Procedure Codes.

Purpose: Widespread conflation of sex assigned at birth and gender has hindered the identification of transgender and nonbinary people in large datasets. The study objective was to develop a method of determining the sex assigned at birth of transgender and nonbinary patients utilizing sex-specific diagnostic and procedural codes, for future use in administrative claims databases, with a goal of expanding the available datasets for exploring sex-specific conditions among transgender and nonbinary people.

Methods: Authors reviewed indexes of International Classification of Diseases (ICD) and Current Procedural Terminology (CPT) codes, and medical record data from a single institution's gender-affirming clinics. Sex-specific ICD and CPT codes were identified through author review and consultation with subject experts. Patient's sex assigned at birth determined by chart review, as a gold standard, was compared with sex assigned at birth determined by querying their electronic health records for natal sex-specific codes.

Results: Sex-specific codes correctly identified 53.5% (n=364) of transgender and nonbinary patients assigned female sex at birth, and 17.3% (n=108) of those assigned male sex at birth. Codes were 95.7% and 98.3% specific for assigned female and male sex at birth, respectively.

Conclusions: ICD and CPT codes can be used to specifically determine the sex assigned at birth in databases where this information is not recorded. This methodology has novel potential for use in exploring sex-specific conditions among transgender and nonbinary patients in administrative claims data.