Rapid Human Cystatin C ELISA Kit
Human Cystatin c (or cystatin 3), which is composed of 120 amino acid residues, belongs to the cystatins superfamilly that inactivates lysosomal cysteine proteinases. As a strongly cationic and low-molecular weight (13.4 kDa) protein, it is almost freely filtered across the glomerular membrane, and is mainly used as a biomarker of kidney function. A growing body of evidence suggests that cystatin c is a more reliable biomarker of glomerular filtration rate than creatinine [1-3].
In addition to kidney disease, altered serum levels of cystatin c are associated with several types of cardiovascular disease, including myocardial infarction, stroke, heart failure, peripheral arterial disease and metabolic syndrome [4-7]. It also seems to play a role in brain disorders involving amyloid, such as Alzheimer's disease [8, 9]. Furthermore, Cystatin c has also been investigated as a prognostic marker in several forms of cancer.
PRINCIPLE OF THE ASSAY
This assay is a sandwich ELISA designed for the quantitative detection of human cystatin c in samples in 1 hour. The immunoplate is pre-coated with antibody specific to human cystatin c. Standards and samples are pipetted into the wells and any human cystatin c present is sandwiched by the immobilised antibody and a second horseradish peroxidase (HRP)-linked antibody specific to human cystatin c that is co-incubated with the samples. After wash step to remove any unbound substances, the HRP substrate solution is added and colour develops in proportion to the amount of human cystatin c bound initially. The assay is stopped and the optical density of the wells determined using a micro-plate reader. Since the increases in absorbance are directly proportional to the amount of captured human cystatin c, the unknown sample concentration can be interpolated from a reference curve included in each assay.
A. Typical representation of standard curve
The following standard curve is provided for demonstration only. A standard curve should be generated for each set of sample assay.
Cystatin c (ng/ml)
Absorbance (450 nm)
The lowest level of human cystatin c that can be detected by this assay is 0.23 ng/ml.
The antibodies used in this assay are specific to human cystatin c and do not cross-react with mouse and rat cystatin c, and other cytokine or hormone molecules.
Intra-assay Precision (Precision within an assay)
Three samples of known concentration were tested 12 times on one plate.
Inter-assay Precision (Precision between assays)
Three samples of known concentration were tested in 10 separate assays.
Serum samples were spiked with different amounts of human cystatin c and assayed.
Average % Recovery