Evaluation of Gentian cystatin C reagent on Abbott Ci8200 and calculation of glomerular filtration rate expressed in mL/min/1.73 m(2) from the cystatin C values in mg/L.
OBJECTIVE
Estimation of the glomerular filtration rate (GFR) is essential when evaluating patients with kidney disease and treating patients with drugs eliminated from the circulation by the kidneys. Cystatin C has been shown in several studies to be superior to creatinine in the estimation of GFR. At our hospitals, there is an increasing demand for cystatin C and at present we perform approximately 1500 cystatin C analyses a month. We thus need the assay available 24 h/day and to have it on our routine chemistry instrument to minimize handling time per test and time to reported test results.


METHODS
We have evaluated a new cystatin C immunoassay from Gentian (Gentian, Moss, Norway) on Architect ci8200 (Abbott Laboratories, Abbott Park, Ill., USA). A prerequisite at our hospital is that cystatin C results are reported as a calculated GFR in mL/min/1.73 m(2), so we also made a comparison with iohexol clearance.


RESULTS
The Gentian cystatin C assay showed good agreement with the corresponding assay from Dade Behring (Deerfield, Ill., USA) and good inter-laboratory concordance. The assay has very low total imprecision, good linearity and strong correlation with iohexol clearance (R (2) = 0.956). The equation for the correlation curve is: y = 79.901x(-1.4389).


CONCLUSIONS
There was low inter-laboratory variation between the three laboratories involved in the cystatin C evaluation, and thus all three laboratories can use the same equation for calculating the estimated GFR.
Flodin
M
M
Department of Clinical Chemistry and Pharmacology, University Hospital, Uppsala, Sweden.
Jonsson
A-S
AS
Hansson
L-O
LO
Danielsson
L-A
LA
Larsson
A
A
D019411:Clinical Laboratory Techniques; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005919:Glomerular Filtration Rate; D006801:Humans; D007472:Iohexol; D007668:Kidney / Q000502:physiology*; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results
C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D007472:Iohexol