ABSTRACT
BACKGROUND: Self-collected capillary samples are convenient for direct access testing (DAT), but exogenous testosterone use may cause falsely elevated total testosterone (TT) results. We designed a quality assurance workflow to differentiate between accurate or erroneous supraphysiological TT concentrations. METHODS: Clinical samples with TT > 1500 ng/dL were reflexed to luteinizing hormone (LH) and follicle stimulating hormone (FSH) and screened for exogenous testosterone use. Samples (n = 120) with normal TT were reflexed to LH/FSH as a control. RESULTS: A total of 8572 TT samples were evaluated, of which 533 (6.2 %) had TT > 1500 ng/dL and were reflexed. Of these, 441 (82.7 %) had significantly decreased LH/FSH (<0.85/<0.7mIU/mL, respectively), 72 (13.5 %) had normal or borderline normal LH/FSH, and 20 (3.8 %) had insufficient plasma volume. In patients with TT > 1500 ng/dL, injectable exogenous testosterone use was most commonly accompanied by significantly decreased LH/FSH, while topical testosterone use was most commonly accompanied by detectable LH/FSH. Control samples were almost all (99.2 %) within or above the LH/FSH reference intervals. Unique patients ordered 351 TT tests where at least one TT result was > 1500 ng/dL. Based on TT and LH/FSH results, we hypothesized that patients were intermittently or consistently overusing exogenous testosterone, resolved elevated TT with recollection, or repeatedly contaminated their sample. CONCLUSION: Self-collected capillary specimens are acceptable for TT testing. A quality assurance reflex to LH/FSH can determine the validity of supraphysiological TT results in a consumer initiated/DAT population.
