Retinol Binding Protein


Sunquest Code:RBP  
Epic Code:LAB3711Epic Name:RETINOL BINDING PROTEIN
Methodology:Nephelometry
CPT Code:83883
Turnaround Time:Specimens are sent to reference laboratory Mon-Sat; results are reported in 1-4 days.


Collection Instructions

Specimen:Blood
Optimal Volume:2 mL
Minimum\Peds Volume:1.2 mL
Container:Red or gold (gel) (Red (no gel))
Causes for Rejection:Severely lipemic or hemolyzed specimen.


Processing and Shipping

Specimen Processing:Separate serum from cells ASAP. Centrifuge and aliquot 1 mL, 0.50 mL minimum. Store in refrigerator.
Shipping Instructions:Ship at refrigerated temperature.
Test Performed at or Referral Lab Lab Sendouts  (ARUP)
Referral Lab number:50467 (RBP)


Interpretive

Reference Range:3-6 mg/dL
Use:Retinol binding protein (RBP) is responsible for binding and transporting retinol (vitamin A). It has a binding site for one molecule of retinol and circulates in the plasma together with prealbumin in the form of a protein complex in a molar ratio of 1:1. This binding to prealbumin prevents greater glomerular losses of the retinol-binding protein. Only the retinol-free form of the retinol-binding protein, which has no affinity for prealbumin, undergoes glomerular filtration unhindered as a result of its low molecular weight; it is re-absorbed by the tubular cells and catabolized there. This explains the elevated serum level of retinol-binding protein in advanced chronic renal insufficiency. Since retinol-binding protein and prealbumin are synthesized in the liver, their serum concentrations are reduced in acute and chronic hepatic diseases. Decreased concentrations have also been observed in cystic fibrosis. Due to the short half-life of RBP (11 hrs), it is an excellent indicator of early malnutrition (half-lives: albumin 21 d, pre-albumin 2 d).


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