Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (712 page)

   Diagnosis and differential diagnosis of DI and psychogenic polyuria

   Diagnosis of SIADH

   Differential diagnosis of hyponatremias

   Interpretation

Increased In

   Nephrogenic DI (partial or complete): high ADH and low osmolality

   Primary psychogenic polydipsia

   SIADH inappropriately increased for degree of plasma osmolality (i.e., normal ADH relative to osmolality)

   Ectopic ADH syndrome

   Certain drugs (e.g., chlorpropamide, phenothiazine, Tegretol)

Decreased In

   Central DI (partial or complete): decreased for level of plasma osmolality

   Psychogenic polydipsia

   Nephrotic syndrome

   Limitations

   Higher secretion occurs at night; in erect posture; with pain, stress, or exercise; and with increased plasma osmolality.