Human cystatin C (or cystatin 3), which is composed of 120 amino acid residues, belongs to the cystatins superfamily 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 therefore 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. The normal range of Cystatin C in plasma sample is 0.5 – 10.3 mg/L. 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.

IMD developed its cystatin C PETIA kit with excellent reproducibility and accuracy equivalent to FDA-approved assays.

This assay is a turbidimetric immunoassay for the quantitative measurement of Cystatin C in human serum, plasma and urine.  A standard or sample is added into a cuvette and mixed with the reaction buffer R1. After a short incubation, the test reagent R2, which is a suspension of microparticles coated with Cystatin C antibodies, is added into the cuvette and mixed. The presence of Cystatin C in the standard or sample causes the immune-particles to aggregate. The extent to which the microparticles aggregate is quantified by the amount of light scattering measured as absorbance by a chemistry analyzer. The concentration of Cystatin C in unknown samples can be interpolated from a reference curve using the standards provided.

TYPICAL STANDARD CURVE

Cystatin C  (mg/L)	Absorbance (570 nm)
0	0.0072
0.5	0.0455
1	0.0920
2	0.1953
4	0.3395
8	0.4547

Assay procedures may vary depending on the automated chemistry analyzer to be used. A general example of assay procedures is stated as follow:

1. Dispense 150µl of R1 into a clean cuvette

2. Add 1.5µl of sample and incubate at 37˚C for 5 minutes

3. Further add 50µl of R2

4. Read change of absorbance at 570 nm for 8 minutes after the addition of R2

5. Calculate the concentration of Cystatin C in unknown sample by interpolation from a reference curve using the standards provided

Cat. No.	Size	Approximately tests
51240 -05	R1: 15ml, R2: 5ml	100
51240 -10	R1: 30ml, R2: 10ml	200
51240 -20	R1: 60ml, R2: 20ml	400
51240 -50	R1: 150ml, R2: 50ml	1000
51240 -100	R1: 300ml, R2: 100ml	2000

For bulk order, please enquire

Product	Catalog           Number	Format	Method
Calibrator	51240-S1	5 x 1ml
Control	51240-C1	2 x 1ml