LAUSR

Abstract Objectives  This study aimed to highlight the necessity of developing and implementing appropriate reference ranges for transgender and nonbinary (TGNB) patient populations to minimize misinterpretation of laboratory results and ensure equitable health care. Case Report  We describe a situation where a TGNB patient's abnormal laboratory values were not flagged due to undefined reference ranges for gender “X” in the Laboratory Information System (LIS). Implementation of additional reference ranges mapped to sex label “X” showed significant improvement in flagging abnormal lab results, utilizing sex-invariant reporting as an interim solution while monitoring developments on TGNB-specific reference ranges. Conclusion  Informatics professionals should assess their institution's policies for registration and lab reporting on TGNB patients as nonimplementation poses significant patient safety risks. Best practices include using TGNB-specific reference ranges emerging in the literature, reporting both male and female reference ranges for clinical interpretation and sex-invariant reporting.