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Spuriously elevated testosterone measurements caused by application of testosterone gel at or near the phlebotomy
1Department of Medicine, Division of Endocrinology, School of Medicine, University of North Carolina, Durham, NC, USA. dkirk@med.unc.edu
Objective:
To report 2 cases of spuriously elevated testosterone measurements caused by contamination of blood samples by testosterone gel applied near the phlebotomy site.
Case Summaries:
A 21-year-old male with primary hypogonadism and a 67-year-old male with secondary hypogonadism were prescribed standard replacement doses of testosterone gel. The patients' symptoms improved without adverse effects. However, their measured testosterone levels rose above the target range and paradoxically increased further despite decreasing the testosterone dose. In both cases, the gel had been applied near the site of venipuncture on the day of blood sampling. Subsequent testosterone measurements from blood obtained after the gel was applied away from the upper/mid arms were in therapeutic range.
Discussion:
To our knowledge, falsely elevated testosterone concentrations due to contamination of blood samples by testosterone gel have been reported only once (PubMed search, 1966-September 2012). In the cases we describe, application of the Naranjo probability scale suggests a probable likelihood that sample contamination caused the falsely elevated testosterone measurements. Health care professionals should recognize and take measures to prevent this problem, which could lead to inappropriate dose changes in hypogonadal patients.
Conclusions:
The application of testosterone gel at or near the site of venipuncture can markedly increase the measured serum testosterone concentration.
