Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1292 page)

   Sample should be frozen immediately to reduce the stability of B
₂
in serum.

Suggested Reading

Russell RM, Suter PM. Vitamin and trace mineral deficiency and excess. In: Fauci AS, Kasper DL, Braunwald E, et al. (eds.).
Harrison’s Principles of Internal Medicine
, 17th ed. New York, NY: McGraw-Hill; 2008:441–449.

VITAMIN B
₆
(PYRIDOXINE)

   Definition

   Vitamin B
₆
is a complex of six vitamers: pyridoxal, pyridoxol, pyridoxamine (pyridoxine), and their 5′-phosphate esters. Because of its role as a cofactor in a number of enzymatic reactions, pyridoxal phosphate (PLP) has been determined to be the biologically active form of vitamin B
₆
. Vitamin B
₆
is important in heme synthesis and functions as a coenzyme in amino acid metabolism and glycogenolysis. Vitamin B
₆
deficiency is associated with symptoms of irritability, weakness, depression, dizziness, peripheral neuropathy, and seizures. In the pediatric population, deficiencies have been characterized by diarrhea, anemia, and seizures.

   
Normal range:
5–50 μg/L.

   Use

   Determining vitamin B
₆
status

   Investigating suspected malabsorption or malnutrition

   Determining the overall success of a vitamin B
₆
supplementation program

   Diagnosis and evaluation of hypophosphatasia

   Interpretation

Increased In

   Hypophosphatasia

Decreased In

   Alcoholism