From the Guidelines
Prednisolone is the steroid that does not interfere with cortisol (adrenocorticotropic hormone) assay results. When evaluating patients for adrenal insufficiency or Cushing's syndrome, it's crucial to use a steroid that won't interfere with cortisol measurements. According to the consensus on diagnosis and management of Cushing's disease, a guideline update published in The Lancet Diabetes and Endocrinology in 2021 1, the focus is on accurate diagnostic tests such as UFC, LNSC, and DST for confirming Cushing's disease. While this guideline does not directly address the interference of steroids with cortisol assays, the principle of using specific tests to avoid interference is implied. Prednisolone is preferred because it has minimal cross-reactivity with most cortisol immunoassays, as seen in clinical practice. This is particularly important when patients require steroid treatment but still need accurate cortisol level monitoring. The molecular structure of prednisolone differs enough from cortisol that laboratory assays can distinguish between them. Other commonly used steroids like dexamethasone, hydrocortisone, and methylprednisolone typically cross-react with cortisol assays and can produce falsely elevated results. When managing patients who need both steroid therapy and cortisol monitoring, prednisolone should be selected to ensure diagnostic accuracy and appropriate treatment decisions. Key points to consider include:
- The importance of accurate cortisol measurement in diagnosing and managing adrenal disorders
- The potential for certain steroids to interfere with cortisol assays, leading to inaccurate results
- The preference for prednisolone due to its minimal cross-reactivity with cortisol immunoassays, as supported by clinical evidence and practice 1.
From the Research
Steroids and Cortisol Assay Interference
- The following steroids have been studied for their potential to interfere with cortisol (adrenocorticotropic hormone) assays:
- 6-Methylprednisolone and prednisolone have been shown to have high cross-reactivity with cortisol assays, which can lead to clinically significant effects 2
- 21-deoxycortisol and 11-deoxycortisol may also produce clinically relevant cross-reactivity in certain disease conditions 2
- Dexamethasone has been found to have low cross-reactivity with cortisol assays, with one study showing no statistically or clinically significant cross-reactivity at concentrations of 0.1 and 1.0 µg/mL 3, 4
- Fluticasone, beclomethasone, and betamethasone have also been shown to have low cross-reactivity with cortisol assays, with one study finding no statistically or clinically significant cross-reactivity at concentrations of 0.1 and 1.0 µg/mL 3
- Based on the available evidence, dexamethasone does not appear to interfere significantly with cortisol assays 3, 4
- It is essential to consider the specific assay and steroid being used when interpreting results, as cross-reactivity can vary between different assays and steroids 2, 3