Elevated Levels of ACTH in a Patient on High Doses of Steroids Treatment: Pitfalls in Steroid Sandwich Immunoassays
2Endocrinology laboratory, Kaplan Medical Center, Rehovot, the Hebrew University of Jerusalem
Introduction:
Accuracy in hormonal testing is necessary in endocrine practice. However, false positive laboratory results can obscure the correct diagnoses.
Aim:
To report the case of falsely elevated ACTH in a young man treated with steroids.
Methods:
Investigate true ACTH levels through analysis of the presence of heterophile and/or nonspecific antibodies.
Case Presentation:
A 18 year- old man was admitted for the investigation of high cortisol and ACTH levels despite high doses of prednisone treatment for autoimmune hepatitis. Medical history and physical examination did not elicit findings of hypercortisolism. Due to lack of response to treatment, noncompliance was suspected. Hypothalamic-pituitary- adrenal axis (HPA) was examined, and the following results were obtained: ACTH level 22 pmol/L (2.2-11.0) and cortisol level 359 nmol/L (119-618 nmol/L). Other pituitary hormonal axes were normal. Levels of renin, aldosterone, DHEA-S, total testosterone, SHBG and androstenedione in the normal range excluded the option of partial glucocorticoid resistance. Interference in ACTH assay was suspected (Immulie 1000 – Simenes), and elimination of nonspecific antibodies was done using Non Specific Antibody Blocking Tube (NABT- Scantibodies). As a result, a low level of ACTH, less than 2.2nmol/l was found in concordance with steroid treatment. Regarding the relatively high cortisol levels, 34% cross-reactivity with prednisone was detected by Siemens (Centaur), analytical platform.
Conclusion:
Interpretation of endocrine testing should always be done in conjunction with clinical assessment of the patient, history of associated diseases, and concomitant medications. Any discrepancy between clinical and laboratory data should raise the suspicion of pitfalls in hormonal immunoassays.
