For the quantitative determination of human cystatin C concentrations in serum, plasma and urine samplesHuman 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 [11, 12].REFERENCES [1] Stevens LA, Coresh J, Schmid CH, et al. (2008) Am J Kidney Dis. 51:395–406. [2] Dharnidharka VR, Kwon C, Stevens G. (2002) Am. J. Kidney Dis. 40 (2): 221–6. [3] Hermida J, Tutor JC. (2006) Ther Drug Monit. 28 (3): 326–31. [4] Zethelius B, Berglund L, Sundström J, et al. (2008) N. Engl. J. Med. 358 (20): 2107–16. [5] Ix JH, Shlipak MG, Chertow GM, Whooley MA. (2007) Circulation 115 (2): 173–9. [6] Deo R, Fyr CL, Fried LF, et al. (January 2008) Am. Heart J. 155 (1): 62–8. [7] Servais A, Giral P, Bernard M, et al. (2008) Am. J. Med. 121 (5): 426–32. [8]Mi W, Pawlik M, Sastre M, et al. (2007) Nat. Genet. 39 (12): 1440–2. [9] Kaeser SA, Herzig MC, Coomaraswamy J, et al. (2007) Nat. Genet. 39 (12): 1437–9. [10] Zurdel J, Finckh U, Menzer G, et al. (2002) Br J Ophthalmol 86 (2): 214–9. [11] Strojan P, Oblak I, Svetic B, et al. (2004) Br. J. Cancer 90 (10): 1961–8. [12] Kos J, Krasovec M, Cimerman N, et al. (2000) Clin. Cancer Res. 6 (2): 505–11.