Rapid Human Cystatin C ELISA kit
C-reactive protein (CRP) is a circulating protein mainly secreted from the liver. This acute phase protein consists of five identical non-glycosylated subunits of 23 kDa, that give rise to a symmetrically arranged globular protein with molecular weight of approximately 120 kDa.1 It has long been recognized that CRP is closely related to immunology, inflammation and host defence; as a result it has been used as an inflammatory marker. However, the development of high-sensitivity CRP (hsCRP) ELISA had addressed its role in other clinical issues. There is accumulating evidence suggesting the important role that CRP plays in mediating cardiovascular diseases (CVD) and type 2 diabetes.2-4 Normally CRP is presenting only in a trace amount in circulation (<1 µg/ml)5,6 but can increase over 1,000-fold under acute inflammatory state. Individual with blood CRP levels <1 µg/ml, 1-3 µg/ml and >3 µg/ml is considered to have low, moderate and high risk, respectively, of CVD and myocardial infraction.7 Therefore, blood CRP level has become a promising measure of CVD risk.8,9
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