ANTIDIURETIC HORMONE (ADH) - plasma

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Specimen: 5 mL blood in EDTA tube. The tube should be pre-cooled and delivered to the laboratory on melting ice, for immediate separation at 4°C and freezing.

Method: Immunoassay.

Reference Interval: Depends on plasma osmolality and intravascular volume.

Application: The test may be used, in conjunction with plasma osmolality, to distinguish between central and nephrogenic diabetes insipidus.

Interpretation: Central diabetes insipidus is associated with low ADH levels, regardless of plasma osmolality. Nephrogenic diabetes inspidus is associated with increasing levels of ADH as plasma osmolality increases.

Reference: Robertson GL. Annu Rev Med 1974; 25: 315-322.

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