Rapid Human Cystatin C ELISA Kit

Rapid Human Cystatin C ELISA Kit

SKU: 31241

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Assay range: 0.23 - 15 ng/mL

Kit Size: 96 wells/kit

Other Names: Cystatin 3, post-gamma-globulin, neuroendocrine basic polypeptide, CST3

  • INTRODUCTION

    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.

  • ASSAY PERFORMANCE

    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)

    Blanked Absorbance

    0

    0.069

    0

    0.23

    0.127

    0.058

    0.46

    0.187

    0.118

    0.93

    0.309

    0.24

    1.87

    0.539

    0.47

    3.75

    0.946

    0.877

    7.5

    1.685

    1.616

    15

    2.551

    2.482

     

    B. Sensitivity

    The lowest level of human cystatin C that can be detected by this assay is 0.23 ng/mL.

     

    C. Specificity

    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.

     

    D. Precision

    Intra-assay Precision (Precision within an assay)

    Three samples of known concentration were tested 12 times on one plate.

    Sample

    Mean (ng/mL)

    SD (ng/mL)

    CV (%)

    1

    507.3

    30.1

    5.9

    2

    377.2

    23.1

    6.1

    3

    137.4

    10.8

    7.9

    Inter-assay Precision (Precision between assays)

    Three samples of known concentration were tested in 10 separate assays.

    Sample

    Mean (ng/mL)

    SD (ng/mL)

    CV (%)

    1

    499.3

    39.0

    7.8

    2

    377.2

    23.1

    6.1

    3

    137.4

    10.8

    7.9

     

    E. Recovery

    Serum samples were spiked with different amounts of human cystatin C and assayed.

    Sample

    Average % Recovery

    Range %

    Serum 

    99

    94-107

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