Interpreting laboratory results in transgender patients on hormone therapy

Clinical guidelines recommend laboratory monitoring of transgender persons on cross-sex hormone therapy, but gender-specific reference intervals leave clinicians with the dilemma of deciding what is "normal" for each patient. The goal of this study was to identify consistent changes in measurands with hormone therapy and determine which reference interval is appropriate.

Laboratory data were abstracted from the medical records of 55 male-to-female patients on hormone therapy and compared with 20 male and 20 female nontransgender subjects.

Hemoglobin, hematocrit, and low-density lipoprotein resembled female values (P < .005), while alkaline phosphatase, potassium, and creatinine resembled male values (P < .05). Triglycerides were higher (P < .005) than either the male or female groups. The remainder of the measurands showed no differences.

Use of correct reference intervals in interpreting laboratory results reduces the risk of testing-related diagnostic error. Preliminary data suggest that new reference intervals need to be established for transgender patients.