Arginine Vasopressin, Plasma 252X Clinical Use Clinical Background • Diagnose central diabetes insipidus Arginine vasopressin (AVP), or (DI) antidiuretic hormone (ADH), is a nonapeptide produced by the hypo- • Differential diagnosis of central DI vs Test Alphabetical nephrogenic DI thalamus and released from the posterior pituitary in response to • Diagnose syndrome of inappropriate extracellular fluid hyperosmolarity and Section ADH secretion (SIADH) hypovolemia. AVP promotes concen- tration of the urine by increasing water Reference Range reabsorption in the kidney tubules. 1.0-13.3 pg/mL Inadequate AVP action causes Note: 2.5 pg = 1 μU diabetes insipidus (DI), a syndrome characterized by nonglycosuric Interpretive Information polyuria, polydipsia, and dehydration. • SIADH Central DI refers to insufficient AVP release due to diseases of the hypo- • Ectopic ADH syndrome thalamus, pituitary stalk, and pituitary • Nephrogenic DI gland. Nephrogenic DI is the result of • Phenothiazine, carbamazepine impaired renal responsiveness to AVP and may be congenital or due to renal • Central DI disease, hypokalemia, hypercalcemia, systemic disorders (eg, multiple myeloma and amyloidosis), or drugs (eg, lithium or demeclocycline and ethanol). DI diagnosis is based on the presence of hyperosmolar serum with in- appropriately dilute urine. Central and nephrogenic DI can be differentiated by measuring the plasma AVP level and interpreting it in light of the simul- taneous plasma osmolality. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is manifest by hyponatremia and inappropriately concentrated urine. The diagnosis is confirmed by plasma or urine AVP levels in- appropriate for serum osmolality. Method • Extraction, radioimmunoassay (RIA) • Analytical sensitivity: 1.0 pg/mL Specimen Requirements 4 mL frozen EDTA plasma 1.1 mL minimum Draw blood in prechilled tube; centrifuge immediately in refrigerated centrifuge. 27.