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Reproductive Endocrinology

SAT-170 - Development of Assay-Specific Serum Total Testosterone Thresholds for the Diagnosis of Male Hypogonadism: A UK-Wide Study

Saturday, June 13, 2026
9:30 AM - 4:30 PM CT
Location: ENDOExpo; Poster Floor


Introduction: Clinical trials have reported benefits of testosterone treatment in symptomatic men with serum total testosterone (TT) concentrations below specified hypogonadal thresholds measured with mass spectrometry (MS). However, over 90% of TT measurements worldwide are immunoassay-derived, precluding accurate application of TT thresholds in practice. Data from a national quality assurance scheme (UK NEQAS) for Steroid Hormones External Quality Assessment (EQA) program were used to define individual immunoassay-specific TT thresholds equivalent to recommended action limits, standardised against a reference liquid chromatography-tandem MS (LC-MS/MS) method.

Methods: All 168 UK National Health Service hospitals each analysed up to 12 identical serum samples within the UK NEQAS program, using one of eight immunoassay platforms (Abbott Architect, Abbott Alinity, Quidel Ortho, Roche Cobas, Siemens Siemens ADVIA Centaur, Roche Cobas Pro, Beckman Access/Dxi, Siemens Atellica) or in-house MS. Measurements were compared with a traceable LC-MS/MS reference method (Joint Committee for Traceability in Laboratory Medicine). Linear regression and Bland–Altman analysis relative to reference method were assessed. Immunoassay-specific TT 95% confidence intervals (CI) equivalent to reference thresholds were interpolated.

Results: A serum TT threshold of 300 ng/dL using reference method was equivalent to the following in ng/dL with 95% CI: 297.1 (291.3 – 302.8, local MS method); 308.6 (302.8 – 317.3; Abbott Architect); 300.0 (297.1 – 302.8, Abbott Alinity); 274.0 (262.5 – 282.7, QuidelOrtho); 317.3 (314.4 – 320.1, Roche Cobas); 300.0 (291.3 – 311.5, Siemens ADVIA Centaur); 317.3 (311.5 – 320.1, Roche Cobas Pro), 271.1 (265.3 - 274.0, Beckman Access); 291.3 (285.5 – 297.1, Siemens Atellica). Similar assay-specific variations were found for other commonly used TT thresholds (e.g. 8 and 12 nmol/L or 276 – 414 ng/dL).

Conclusions: We report immunoassay-specific confidence intervals equivalent to serum TT thresholds interpolated against a reference LC-MS/MS method, below which evidence for clinical benefit has been reported in symptomatic older men. These results may help clinicians, particularly in low-middle-income settings, to more accurately identify and exclude male hypogonadism.

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