Impact of old and current immunoassays on the 1 mg overnight dexamethasone suppression test: comparison with LC-MS/MS
Authors' conclusion
Both immunoassays demonstrated remarkable underdetection of hypercortisolism, suggesting the application of a method-specific cutoff. Immunoassay performance may not be uniform in basal and post-DST conditions and should be purposely examined. Accurate LC-MS/MS methods should be preferred in hypercortisolism settings.
Study context
- Population
- Patients with suspected hypercortisolism or adrenal incidentalomas, post-DST sera
- Comparison
- Elecsys gen I and Access immunoassays vs LC-MS/MS for post-DST cortisol
- Elecsys gen In = 260
- Accessn = 217
- Outcome
- Effectiveness of immunoassays in detecting hypercortisolism vs LC-MS/MS (50 nmol/L cutoff)
Main finding
As reported in the abstract
Hypercortisolism detection at 50 nmol/L cutoff
- Both immunoassays detected lower rates of hypercortisolism vs LC-MS/MS, particularly in adrenal adenomas
- P < .050
- Possible false negatives, Elecsys gen I
- 6.9%
- Possible false negatives, Access
- 6.4%
- Possible false positives, Elecsys gen I
- 3.8%
Further findings
| Outcome | Elecsys gen I | Access |
|---|---|---|
| Optimal immunoassay-specific cutoff | 41 nmol/L | 33 nmol/L |
| Sensitivity | 97.7% | 97.5% |
| Specificity | 80.8% | 78.3% |
Deviation from LC-MS/MS cortisol in basal and post-DST samples
- Elecsys gen I overestimation, basal
- 32.5%
- Elecsys gen I overestimation, post-DST
- 6.1%
- Access underestimation, basal
- −4.7%
- Access underestimation, post-DST
- −5.9%
- Sex differences in method deviations were noted
Original publication
Impact of old and current immunoassays on the 1 mg overnight dexamethasone suppression test: comparison with LC-MS/MS. Eur J Endocrinol. Published 14 July 2025. doi:10.
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