Retinol Binding Protein

Immunology

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Description

Retinol binding protein (RBP) is a small molecular weight protein of 21KDa, the prime function of which is to bind and transport retinol. It exists in the serum mainly in the form of a complex with transthyretin (previously known as prealbumin or thyroxine-binding prealbumin - TBPA), by which means it is preserved from renal filtration. Tubular proteinuria results from a decrease in the capacity of the renal tubules to reabsorb protein and results in an increase in excretion of low molecular weight proteins. The free form of RBP is readily filtered by the glomerulus and reabsorbed by the renal tubules [1]. Urinary levels may be used in the assessment of renal tubular function when investigating tubular proteinuria [1]. Measurement of serum RBP levels has limited use in the assessment of nutritional status of pateints [1,2]. Low levels of serum RBP are seen in vitamin A deficiency, therefore it has been proposed that RBP can be used as an indicator of vitamin A status [3].

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Indications

Serum RBP for Nutritional / Vitamin A status (limited use); Urine RPB for Renal tubular dysfunction.

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Sample Type

2mL Serum (Gel 5mL Yellow tube) or 20mL Urine. Requests from outside Sheffield: Transport at ambient temperature via Royal Mail or Courier.

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Reference Range

Serum 20 - 40 mg/L.Urine <15 mg/L.Reference ranges established in house.

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Turnaround Time

Within 10 days

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Testing Frequency

Weekly

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References

PRU Handbook of Clinical Immunochemistry. 9th Edition. 2007. [Ref 1]Raguso CA, Dupertuis YM, Pichard C. The role of visceral proteins in the nutritional assessment of intensive care unit patients. 2003. Curr Opin Clin Nutr Metab Care. 6(2):211-216. [Ref 2]De Pee, S and Dary O. Biochemical indicators of vitamin A deficiency: Serum retinol and serum retinol binding protein. J Nutri. 2002. 132(9):2895S-2901S. [Ref 3]

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See Also

Urine Protein Clearence ratio ; Transthyretin/Pre-Albumin

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