Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1282 page)

   Macroglobulinemia

   Sjögren syndrome

   SLE

   Lymphoproliferative disorders

   Hyperglobulinemia associated with cirrhosis

   Chronic active hepatitis

   Acute thermal burns

Decreased In

   No clinical significance

   Limitations

   Whole blood measurement is of limited use because of differences in shear rates between instrumentation and in vivo conditions.

   Clinical symptoms do not correlate well with test results.

VITAMIN A (RETINOL, CAROTENE)

   Definition

   Vitamin A is a subclass of a family of lipid-soluble compounds referred to as retinoic acids. There are essentially three forms of vitamin A: retinols, betacarotenes, and carotenoids. Retinol, also known as preformed vitamin A, is the most active form and is mostly found in animal sources of food. Betacarotene, also known as provitamin A, is the plant source of retinol from which mammals make two thirds of their vitamin A. Carotenoids, the largest group of the three, contain multiple conjugated double bonds and exist in a free alcohol or in a fatty acyl ester form. Vitamin A promotes normal vision and prevents night blindness; contributes to growth of bone, teeth, and soft tissues; supports thyroxine formation; maintains epithelial cell membranes, skin, and mucous membranes; and acts as an anti-infection agent.