New ELISA Kit Measures Chronic Kidney Disease Biomarker

A new ELISA kit has been released that is expected to become a valuable tool for researchers investigating new biomarkers that could improve prediction of chronic kidney disease (CKD) progression, as well as discovery of new drug targets.

The emergence of FGF23 as a potentially modifiable risk factor in CKD has led to growing interest in its measurement as a tool to assess patient risk and target therapy. In this regard, Biomedica Immunoassays (Vienna, Austria) has launched the first European CE marked FGF23 (C-terminal) ELISA assay that specifically detects both intact and C-terminal fragments of FGF23 in human serum and plasma. FGF23 (fibroblast growth factor 23) is a 32 kDa protein with 251 amino acids that is proteolytically processed between arginine179 and serine180 to generate N-terminal and C-terminal fragments. FGF23 is mainly secreted by osteocytes and controls phosphate and 1,25(OH)2 vitamin D homeostasis.

The kit comprises a sandwich enzyme immunoassay for the direct determination of FGF23 in human serum and plasma samples. In a first step, standards, samples, controls, and detection antibody (rabbit polyclonal anti-human FGF23-biotin) are dispensed into the wells of microtiter strips, which have been pre-coated with anti-FGF23 antibody. FGF23 present in the standards, samples, or controls binds to the pre-coated antibody in the well and forms a sandwich with the detection antibody. In the washing step all nonspecific unbound material is removed. In a second step, the conjugate (Streptavidin-horse radish peroxidase) is added to the wells and reacts with the detection antibody through avidin-biotin binding. After another washing step, the TMB (tetramethylbenzidine) substrate is dispensed into the wells. The enzyme catalyzed color change of the substrate is directly proportional to the amount of FGF23. This color change is detectable with a standard microtiter plate ELISA reader. A dose response curve of the absorbance (optical density at 450 nanometers) versus standard concentration is generated, using the values obtained from the standard. The concentration of FGF23 in the sample is determined directly from the dose response curve.

FGF23 is associated with cardiovascular and renal outcomes in patients with CKD and adds value to risk assessments based on conventional risk factors. “In particular, the ability to measure FGF23 in both serum and plasma samples and its stability in both matrices after sample collection opens up a significant new capability to learn about the mechanisms driving FGF 23 elevations in CKD,” said Dr. Wolfgang Woloszczuk, CSO of Biomedica Gruppe.


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