Is radioimmunoassay for antidiuretic hormone (ADH)/arginine vasopressin (AVP) useful in the diagnosis of syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

Updated: Aug 16, 2019
  • Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN  more...
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The use of radioimmunoassay for ADH/AVP may provide supportive evidence for the diagnosis of SIADH. However, the values are not usually available quickly enough to assist in clinical decision making.  Furthermore AVP is unstable with a short half life, making levels unpredictable.  In contrast, co-peptin is a stable C-peptide fragment of the AVP precursor protein which is easier to measure and can be used to evaluate hyponatremia and even to classify the osmoregulatory defects in SIADH. [4, 29]

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