Measurement of iohexol by capillary electrophoresis: minimizing practical problems encountered.
Iohexol is a non-ionic contrast agent, which has been widely described in recent literature as an accurate marker for the measurement of glomerular filtration rate (GFR). Our aim was to establish a capillary electrophoresis assay, based on a previously described method, that had adequate reproducibility to be used as part of a clinical trial. In this paper, we examine the practical aspects, pitfalls and steps we took to achieve a precise and reproducible assay. To minimize laboratory variation, we examined properties such as the use of an internal standard in a capillary electrophoresis separation, alternative deproteinization methods for serum, the most suitable matrix for the dilution of standards and the implementation of suitable quality control material to ensure that run-to-run variability was minimized. The optimized capillary electrophoretic assay of iohexol was found to be robust, with over 860 runs from the one capillary over a 9-month period. Excluding capital costs of the instrument, the consumable cost of the assay is less than A$0.25 per test, with a run time of 5.25 min and a coefficient of variation (CV) of 4.3% at 80 mg/L. The GFR, calculated from the plasma clearance, had a reproducibility of 5.47%.
Jenkins
M A
MA
Division of Laboratory Medicine, Austin and Repatriation Medical Centre, Heidelberg, Vic., Australia. majenkins@austin.unimelb.edu.au
Houlihan
C
C
Ratnaike
S
S
Jerums
G
G
Des Parkin
J
J
D000097:Acetonitriles / Q000494:pharmacology; D003287:Contrast Media / Q000032:analysis*; D019075:Electrophoresis, Capillary / Q000379:methods*; D005919:Glomerular Filtration Rate; D006801:Humans; D007472:Iohexol / Q000032:analysis*; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
D000097:Acetonitriles; D003287:Contrast Media; D007472:Iohexol; C032159:acetonitrile