• Assay Type Competitive ELISA
  • Sample Types Serum, Plasma, Urine, Dried Blood Spots
  • Sensitivity 5.69 ng/mL (10 µL), 1.36 ng/mL (100 µL)
  • Species Human
  • Assay Duration 1.5 Hours
  • Samples/Plate 38 in Duplicate
  • Readout Colorimetric, 450 nm
  • Standard Curve Retinol Binding Protein (RBP) Multi-Format ELISA Kit
  • Description

    Assay Principle: 

    The Retinol Binding Protein (RBP) Multi-Format ELISA Kit quantitatively measures RBP in urine, serum, plasma, and dried blood spots. The Retinol Binding Protein (RBP) Multi-Format ELISA Kit is a competitive ELISA with a run time of 1.5 hours. Please read the complete kit insert for more information before performing this assay.

    Use our provided RBP standard to generate a standard curve for the assay. Pipette the standards or diluted samples into a transparent microtiter plate coated with our donkey anti-sheep IgG antibody. Add the RBP peroxidase conjugate and the RBP sheep polyclonal antibody. Then incubate the mixture covered at room temperature, shaking for 1 hour. The immunological reaction occurs between the anti-RBP antibody, the RBP antigen in the sample or standard, and the RBP conjugate. As the RBP concentration in the sample increases, the bound RBP-peroxidase conjugate decreases, causing a decrease in signal and vice versa. 

    After the 1-hour incubation, wash away the excess RBP-peroxidase conjugate and add the TMB substrate. The TMB substrate reacts with the bound RBP-peroxidase conjugate generating a signal detected by a plate reader at 450nm. Use the intensity and the standard curve to calculate the RBP concentration in the samples.


    Retinol binding protein (RBP) is from a family of structurally related proteins that bind small hydrophobic molecules such as bile pigments, steroids, odorants, etc. RBP is a 21 kDa highly conserved, single-chain glycoprotein consisting of 182 amino acids with 3 disulfide bonds, with a hydrophobic pocket that binds retinol. RBP is filtered by the glomeruli and reabsorbed by proximal tubules. Its filtration makes it a valuable marker in urine for renal function in heart or kidney transplant recipients, type 1 and 2 diabetics, and people exposed to uranium from mining operations. Modulating RBP4 levels may lead to new strategies in treating type 2 diabetes.

    In serum, most RBP bound with retinol is reversibly complexed with transthyretin. This complex transports retinol to specific receptors of various tissues in the body. RBP is a useful surrogate marker for retinol because of the correlation between retinol and RBP in serum, which implies that RBP may be used to monitor vitamin A deficiency (VAD). Measurement of RBP levels has also helped detect and characterize diseases, including hypertension and certain cancers, among other conditions. The WHO has estimated that 250 million children have moderate to severe VAD due to inadequate nutrition. The rising cost of food staples worldwide further exacerbates this problem. In addition to nutritional deficiencies, infectious stresses can depress retinol concentrations. Individuals with diseases such as cystic fibrosis and HIV-1 also risk VAD due to the infectious stresses contributing to the disease.