Approach to interpreting common laboratory pathology tests in transgender individuals.

CONTEXT As the number of transgender (trans) people (including those who are binary and/or non-binary identified) seeking gender-affirming hormone therapy rises, endocrinologists are increasingly asked to assist with interpretation of laboratory tests. Many common laboratory tests such as hemoglobin, iron studies, cardiac troponin and creatinine are affected by sex steroids or body size. We seek to provide a summary of the impact of feminizing and masculinizing hormone therapy on common laboratory tests and an approach to interpretation. CASES Case scenarios discussed include 1) hemoglobin and hematocrit in a non-binary person undergoing masculinizing hormone therapy; 2) estimation of glomerular filtration rate in a trans woman at risk of contrast-induced nephropathy; 3) prostate-specific antigen (PSA) in a trans woman; and 4) chest pain in a trans man with a cardiac troponin concentration in-between the reported male and female reference ranges. CONCLUSIONS The influence of exogenous gender-affirming hormone therapy on fat and muscle distribution and other physiological changes determines interpretation of laboratory tests which have sex-specific differences. In addition to affirmative practice to ensure a patient's name, gender and pronoun are used appropriately, we propose that once individuals have commenced gender-affirming hormone therapy, the reference range of the affirmed gender be reported (and specified by treating clinicians) except for PSA or cardiac troponin which is dependent on organ size. Whilst suggestions may be challenging to implement, they also represent an opportunity to lead best practice to improve the quality of care and experiences of healthcare for all trans people.