Patent ID: 8158443

Claim:
A turbidimetric immunoassay method for assessing human Cystatin C in a human body liquid sample comprising a) forming an assay mixture by contacting said sample with a nanoparticle-antibody conjugate comprising nanoparticles suitable for turbidimetric measurement, wherein said nanoparticles are coated with anti-human Cystatin C antibodies or antigen binding fragments thereof, to bind said Cystatin C, wherein said coated nanoparticles are coated with 5 to 35% of binding antibody per total weight of nanoparticle-antibody conjugate and wherein said coated nanoparticles have a median diameter in the range of 59 to 160 nm, and b) assessing the human Cystatin C content by measuring the change in turbidity of said mixture by determining the absorbance change at at least one wavelength in a range between above 370 nm and below 500 nm; thereby assessing human Cystatin C in a human body liquid sample.