| name | icsm-choose-testosterone-assay-method |
| description | Recommends mass spectrometry for research purposes and good-quality immunoassays for routine clinical diagnosis when standardized against an international reference range. Triggers when a clinician orders a testosterone test and asks "which assay should I use?" or questions "is this immunoassay reliable enough?" |
Select appropriate testosterone assay method for diagnosis
STEP 1 — Gather Information
Determine assay purpose (research vs clinical), verify sample timing (fasting, 07:00–11:00), identify assay platform (mass spectrometry or immunoassay), and check if immunoassay is standardized against an internationally harmonized reference range.
STEP 2 — Rule In / Rule Out
Is the assay intended for research?
- Yes → proceed to Step 3 for research preference.
- No (clinical diagnosis) → proceed to Step 3 for clinical acceptability.
STEP 3 — Classify or Stratify
For research: mass spectrometry is the gold standard.
For clinical: Is the immunoassay good-quality and standardized against an international reference range?
- Yes → immunoassay acceptable for diagnosis.
- No → immunoassay not reliable; consider mass spectrometry or send sample to a certified reference lab.
STEP 4 — Decide
- Research: Use mass spectrometry.
- Clinical & standardized immunoassay: Use the immunoassay.
- Clinical & non‑standardized immunoassay: Use mass spectrometry or refer sample to a lab with a validated, standardized assay.
Clinical Guardrails / Mimics / Pitfalls
Do not rely on non‑standardized immunoassays for diagnostic decisions; avoid using immunoassay results without verification of standardization; do not substitute immunoassay for mass spectrometry in research settings; avoid testosterone measurement during acute illness; ensure fasting morning sample collection.
Concrete Clinical Example
A 45‑year‑old man presents with low libido and fatigue. The clinician orders a morning testosterone test, confirms the hospital immunoassay is CDC‑harmonized and calibrated to the international reference range, and proceeds with the immunoassay for clinical diagnosis.
Source: Male hypogonadism: recommendations from the Fifth International Consultation on Sexual Medicine (ICSM 2024), International Society for Sexual Medicine, 2025, DOI: 10.1093/sxmrev/qeaf036
