At-Home Cortisol Testing: Brand Reliability Assessment
No specific at-home cortisol testing brand can be recommended as reliable for clinical diagnosis, as current medical guidelines do not validate or endorse any commercial at-home cortisol testing kits for diagnosing Cushing's syndrome or adrenal disorders. 1, 2
Why At-Home Tests Are Not Guideline-Recommended
The Endocrine Society guidelines specifically recommend late-night salivary cortisol (LNSC) testing as one of the screening modalities for Cushing's syndrome, but this requires laboratory-based analysis using validated methods—not consumer at-home interpretation. 1
Critical Laboratory Requirements
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the gold standard for measuring salivary cortisol due to superior specificity and sensitivity compared to immunoassays. 3, 4
Direct immunoassays used in many commercial kits have significant problems with specificity and show substantial inter-assay differences, making results unreliable without proper extraction and prepurification. 3, 4
Salivary cortisol measurement requires validated reference ranges that are age-dependent and method-specific, which commercial at-home kits typically do not provide. 5, 6
Proper Clinical Approach to Cortisol Testing
If Cushing's syndrome is suspected, the Endocrine Society recommends starting with dexamethasone suppression test (DST), 24-hour urinary free cortisol (UFC), and/or late-night salivary cortisol (LNSC) depending on local laboratory availability. 1
Salivary Cortisol Collection Protocol
Collect at least two to three late-night salivary samples (around 10:00 PM or at bedtime) for proper screening. 1
Samples must be sent to a clinical laboratory using LC-MS/MS or validated radioimmunoassay methods, not analyzed with at-home devices. 3, 4
Age-dependent cut-off values are essential: for adults aged 21-60, a midnight salivary cortisol >1.9 μg/L has 97.6% sensitivity and 100% specificity for Cushing's syndrome. 5
Common Pitfalls with At-Home Testing
Consumer-grade cortisol tests lack the analytical validation required for clinical decision-making and may use inferior immunoassay methods with poor specificity. 3, 4
Salivary cortisol reflects unbound (free) cortisol and requires proper timing (late-night collection) to detect loss of circadian rhythm, which is the key diagnostic feature. 4, 5
Multiple concordant normal screening tests across different modalities are needed to effectively exclude Cushing's syndrome—a single at-home test cannot accomplish this. 2
Recommended Action
Work with your healthcare provider to order laboratory-based late-night salivary cortisol testing through a clinical laboratory that uses LC-MS/MS methodology. 1, 3, 4 This ensures proper sample handling, validated analytical methods, and appropriate reference ranges for accurate interpretation.