Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (711 page)

   Cutoff concentrations:

   10–50 ng/mL ELISA

   300 or 500 ng/mL EIA qualitative

   150 ng/mL EIA semiquantitative

   Variable cross-reactivity with other TCAs, metabolites: consult the manufacturer’s package insert.

   Will not detect SSRIs and newer antidepressants.

   No SSRI-specific immunoassays are currently available.

   General drug screens comprising alkaline liquid–liquid extraction or solid-phase extraction followed by GC/MS or gas chromatography analysis detect TCAs, SSRIs, trazodone, bupropion, venlafaxine, mirtazapine, and amoxapine with limit of detection ranging from 20 to 250 ng/mL.

ANTIDIURETIC HORMONE

   Definition

   Antidiuretic hormone (ADH), also known as vasopressin or arginine vasopressin, is a hormone secreted by the posterior pituitary. It regulates the water permeability of renal collecting ducts and urine concentrating ability by increasing water reabsorption, which is mediated by transcellular water channels (aquaporins).

   
Normal range:
<1.5 pg/mL (see Table 16.9 for effect of plasma osmolality on ADH levels).

TABLE 16–9. Plasma Osmolality Influences on ADH Levels

   Use