What's a Normal Lab Result for a Transgender Patient?

November 14, 2013

By Will Boggs, MD

NEW YORK (Reuters Health) Nov 14 - Transgender patients on hormone therapy should have their own laboratory reference ranges, researchers say.

"We realize that since information regarding this population is lacking in medical education, many providers may never have considered the unique challenges that accompany their care," Dr. Tiffany K. Roberts from Emory University School of Medicine in Atlanta, Georgia, told Reuters Health.

"Laboratory monitoring is just one of those challenges, but it's an important one since many care decisions are guided by laboratory results," she said.

Many routine laboratory results are reported with gender-specific reference interval, but it's unclear which is appropriate for a transgender patient.

Dr. Roberts and colleagues examined 55 male-to-female patients, ranging in age from 27 to 67 (median 46), who'd been on hormone therapy for at least six months. They also included 20 males and 20 females who hadn't switched genders.

Alanine aminotransferase and aspartate aminotransferase levels did not differ between male, female, and male-to-female groups, but alkaline phosphatase values in the transgender group were closer to those for males, the authors reported October 19 online in The American Journal of Medicine.

Blood urea nitrogen values were similar among the groups, but creatinine values for transgender patients resembled male values. On the other hand, hemoglobin and hematocrit values for transgender patients resembled female values.

For transgender patients, LDL levels resembled female values, triglyceride levels were higher than those for males or females, and HDL values were intermediate between those for males and females.

"These data indicate that it is impossible to predict which reference range is most appropriate for male-to-females based solely on what is known about hormone therapy in post-menopausal women or the effects of endogenous estrogen on healthy patients of either gender," the researchers conclude. "Laboratories should empirically determine reference ranges specifically for male-to-female and female-to-male patients on hormone therapy in order to facilitate patient safety and avoid diagnostic error."

"It is our hope that clinicians that read this article will realize that if lab values for a transgender patient on hormone therapy do not fall within the provided reference interval it does not necessarily indicate the need for follow-up and may be a part of the desired physiological changes associated with the therapy," Dr. Roberts said.

"Our findings describe what the expected changes are for the most routinely monitored (measures)," he added. "This information can guide clinicians in differentiating between a value outside the reference interval that is expected and one that requires follow-up."

"Having an empirically determined reference interval is advisable for hospitals that follow a larger population of transgender persons," Dr. Roberts said. "But that strategy is not feasible for many primary care providers or even large health systems in areas with a smaller transgender population. In these cases, being aware of these findings will put providers more at ease when a laboratory value falls outside of the reference interval that was established for a non-transgender population and, thereby, reduce unnecessary follow-up."

Dr. Joshua D. Safer, who cares for transgender patients at Boston University Medical Center, told Reuters Health by email that the lab tests covered in the study "fall into four categories":

1. Values where clinically relevant abnormal values exceed normal by some factor (e.g., liver function testing);

2. Values where clinical decisions are made based on absolute numbers, not the male vs female ranges (e.g., cholesterol profiles, electrolytes);

3. Values where the differences are considered in the context of body size (e.g., creatinine); and

4. Values where there are differences mediated at least in part by hormones.

"This latter category contains the values where knowing the relative harm (or benefit) from the transition could be clinically useful," Dr. Safer said. "For the first three...the differences between men and women are not clinically important. Therefore, there is no real concern for transgender individuals."

"While the interpretation of many laboratory values does not change for transgender individuals undergoing hormone therapy, there are a number of important values for which the interpretation does change," Dr. Safer said. "The degree of harm or benefit from such shifts remains a topic for future study to determine if there is anything that might be considered to mitigate any harm. In the interim, a prudent course might be to address abnormal values in the usual fashion (e.g. cholesterol profiles) which luckily is mostly done in similar fashion for both men and women anyway."

Dr. Maddie Deutsch, Clinical Lead for the Center of Excellence for Transgender Health at the University of California, San Francisco, told Reuters Health by email, "The preliminary findings reported here, limited in size and scope, reinforce existing anecdotal practice that certain lab values should be interpreted in the context of a trans patient being on hormones."

"The statistical significance found in this study does not appear to be in a clinically significant range, with the exception of hemoglobin/hematocrit (Hgb/Hct) and creatinine (Cr)," Dr. Deutsch said. "Cr is of importance because providers may interpret a Cr as 'elevated' in a trans woman if female ranges are used - and if the patient is taking spironolactone as an anti-androgen, this could lead to the provider being concerned about drug-induced renal insufficiency. Low Hgb with what would likely be a normal MCV might raise concern for blood loss. I'm not surprised to see lower Hgb/Hct in people from whom testosterone has been removed."

"As with many aspects of caring for transgender patients, interpretation of lab results requires an extra analysis step which involves considering the patient's birth sex, current hormonal gender, and reference ranges used by the lab for the particular test in question," Dr. Deutsch said.

"While I agree that general misinformation about trans care among providers is endemic, I disagree with the author's assertion that evidence supports routine hormone monitoring," Dr. Deutsch added. "There is no evidence to support this practice beyond the weakly evidence-based expert opinion expressed in the endocrine society guidelines."

SOURCE: http://bit.ly/1e6rz0U

Am J Med 2013.

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