Name of the Test: Vitamin D Binding protein
Alias Names: High affinity Vitamin D binding protein, Vitamin D BP, DBP, GC globulin, GC protein

Vitamin D binding protein determination is useful in Determining the bioavailable vitamin D (25 hydroxy as well as 1, 25 di hydroxyl vitamin D) Determining the changes in liver failure, type I diabetes, cystic fibrosis and in pregnancy.

Clinical Applications: Vitamin D binding protein (DBP) is a circulating glycoprotein with a molecular weight of 52 Kd . It is produced by the liver and kidney and acts as a high affinity carrier protein for 25 hydroxy and 1,25 di hydroxyl vitamin D. DBP is the same carrier protein for vitamin D2, Vitamin D3 and other metabolites . Gc-globulin is the major chemotactic enhancing factor in serum and may function as an up-regulator of the chemotactic activity of C5-derived peptides. Circulating levels of Vitamin D BP is increased during pregnancy and also in individuals who had hormonal therapy (estrogen).Gc-globulin is the major chemotactic enhancing factor in serum and may function as an up-regulator of the chemotactic activity of C5-derived peptides replacement therapy or estrogenic contraceptives. The levels are decreased in liver failure, liver disease, Type I Diabetes and cystic fibrosis. Decreased DBP levels were reported in serum samples from several patients at risk of developing multi-organ failures (trauma and sepsis).

Methods: Vitamin D BP is quantitated using a sandwich immunoassay using monoclonal antibodies , one as capture and other as tag antibody , conjugated with horse raddish peroxidase (HRP). The color is developed and read at 450 nm .The Optical density is directly proportional to the concentration of DBP. Monoclonal antibodies are capable recognizing all the fractions of Vitamin D BP.
Test Information:
Test Code # 123
Specimen requirements:
1 ml (minimum 0.2 ml) serum or plasma
Shipping requirements: Ship the samples frozen or in ice packs. Shipping samples at room temperature is not recommended.
Turnaround time: 1 day (setup every Tuesday)
Reference Range: 104 – 477 ug /ml
If the Vitamin D ( 25 OH) concentration and serum albumin are provided by the client, we could calculate bioavailable vitamin D using Vitamin D binding protein concentration.

THIS TEST IS APPROVED BY NEW YORK STATE.

References:

  1. Lauridsen AL, Vestergaard P and Nexo E (2001) Mean Serum Concentration of Vitamin D-binding Protein (Gc Globulin) Is Related to the Gc Phenotype in Women. Clin Chem 47: 753 – 756.
  2. Vinholt F et al (1997) Reduced serum GC-globulin concentrations in patients with fulminant hepatic failure: Association with multiple organ failure Critical care Medicine 25: 1366 – 1370.
  3. Blanton D et al (2011) Reduced serum vitamin D – Binding protein levels are associated with Type 1 Diabetes. Diabetes 60: 2566 -2570.