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Serum cortisol assay performance following the 1 mg overnight dexamethasone suppression test
Jonathan S Atkins1, James M Hawley1, Laura J Owen2,3
1Department of Clinical Biochemistry, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK.
Insights
The 1 mg overnight dexamethasone suppression test (ONDST) performance varies by immunoassay platform. Roche and Siemens assays showed closer alignment with LC-MS/MS, while Abbott may reduce ONDST sensitivity, necessitating assay-specific cut-offs.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Laboratory Medicine
Background:
- The 1 mg overnight dexamethasone suppression test (ONDST) is crucial for diagnosing Cushing's syndrome and evaluating adrenal incidentalomas.
- Significant variations exist in serum cortisol immunoassay performance, yet their impact on ONDST results is under-researched.
Purpose of the Study:
- To evaluate and compare the performance of three common immunoassay platforms (Roche Elecsys II, Abbott Alinity, Siemens Centaur) for serum cortisol measurement during ONDST.
- To assess these platforms against a gold-standard liquid chromatography tandem mass spectrometry (LC-MS/MS) method.
Main Methods:
- Seventy-seven anonymized patient samples from ONDSTs were analyzed using Roche, Abbott, and Siemens immunoassay platforms.
- Results were statistically compared to a validated LC-MS/MS method, excluding samples with factors affecting immunoassay quality.
Main Results:
- The Roche Elecsys II demonstrated minimal bias (-2.4 nmol/L) and strong correlation (y = -0.9 + 0.97x) with LC-MS/MS.
- The Siemens Centaur also showed good agreement (bias 2.3 nmol/L, y = 1.4 + 1.07x), with minor sex-based differences.
- The Abbott Alinity exhibited significant bias (-18.8 nmol/L) and weaker correlation (y = -11.3 + 0.88x), with notable differences between sexes.
Conclusions:
- Method-dependent variations in serum cortisol assays significantly impact ONDST results.
- Roche and Siemens platforms offer reliable performance comparable to LC-MS/MS for ONDST.
- The Abbott platform may compromise ONDST sensitivity, highlighting the need for assay-specific diagnostic cut-offs.
Background:
The 1 mg overnight dexamethasone suppression test (ONDST) is recommended for the differential diagnosis of Cushing's syndrome and the investigation of adrenal incidentalomas. Despite documented variation in serum cortisol immunoassay performance, little has been published regarding its effect on the ONDST.
Aims:
Assess the performance of three immunoassay platforms (Roche Elecsys II, Abbott Alinity & Siemens Centaur) when compared to a liquid chromatography tandem mass spectrometry (LC-MS/MS) method.
Methods:
Samples (n = 77) sent to the laboratory as part of an ONDST were retrieved prior to disposal, anonymized, and analysed on all platforms. Samples with factors impacting immunoassay analysis quality were excluded. Results were statistically compared to an LC-MS/MS method that previously demonstrated excellent comparability to a candidate reference method.
Results:
The Roche gen II showed a mean bias of -2.4 nmol/L and a Passing-Bablok fit of y = -0.9 + 0.97x. This was not affected by sex. The Abbott showed a mean bias -18.8 nmol/L, and a fit of y = -11.3 + 0.88x. This bias was -20.7 nmol/L in females versus -17.2 nmol/L in males. The Siemens had a mean bias of 2.3 nmol/L and a fit of y = 1.4 + 1.07x. This bias was 5.7 nmol/L in males versus -1.0 nmol/L in females.
Conclusions:
Clinicians should be aware of the method-dependent variation that exists within serum cortisol analysis during the ONDSTs. Roche and Siemens aligned more closely with LC-MS/MS while the Abbot may cause a reduction in ONDST sensitivity. This data supports assay-specific cut-offs for the ONDST.
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