Improved immunoturbidimetric assay for cystatin C.
An immunoturbidimetric assay for cystatin C was optimized with respect to assay imprecision. After investigating the optimum pH, polyethylene glycol concentration and specimen volume, two modifications were introduced: an increase in specimen volume to 25 microL; and an extension of the pre-incubation period to 240 s. These modifications produced an assay with between-batch imprecision (coefficient of variation, n = 10 or 11) ranging from 3-9% at 0.72 mg/L to 1.3% at 5.29 mg/L. The assay was susceptible to interference from lipaemia and haemolysis but not bilirubinaemia in both the original and modified protocol. Extending the pre-incubation to 240 s improved tolerance to common interferences and retained assay applicability in the routine clinical setting.
Department of Clinical Biochemistry, Oxford Radcliffe Hospital, Headington, UK.
A V
AV
Lewis
T J
TJ
James
J B
JB
McGuire
R P
RP
Taylor
D000136:Acid-Base Equilibrium / Q000276:immunology*; D001663:Bilirubin / Q000032:analysis / Q000097:blood; D003404:Creatinine / Q000032:analysis / Q000097:blood; D055316:Cystatin C; D015891:Cystatins / Q000032:analysis* / Q000097:blood / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007118:Immunoassay / Q000379:methods; D007070:Immunoglobulin A / Q000032:analysis / Q000097:blood / Q000276:immunology; D066298:In Vitro Techniques; D007700:Kinetics; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D011092:Polyethylene Glycols / Q000737:chemistry; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013696:Temperature; D013997:Time Factors; D014280:Triglycerides / Q000032:analysis / Q000097:blood; D008258:Waldenstrom Macroglobulinemia / Q000097:blood / Q000276:immunology
C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D007070:Immunoglobulin A; D011933:Reagent Kits, Diagnostic; D014280:Triglycerides; D011092:Polyethylene Glycols; D003404:Creatinine; D001663:Bilirubin