Comparison of acid and enzymatic methods for insulin dosage: Analytical performances and impact on glomerular filtration rate evaluation

in Clinica Chimica Acta (2012), 413(5-6), 556-560

Among issues susceptible to hamper a reliable measurement of inulin clearance, those regarding the dosage of inulin are largely neglected. We have compared the analytical performances of 2 commonly used ... [more ▼]

Among issues susceptible to hamper a reliable measurement of inulin clearance, those regarding the dosage of inulin are largely neglected. We have compared the analytical performances of 2 commonly used methods of inulin dosage (one “acid” and one “enzymatic” method) and studied their potential impact on the glomerular filtration rate (GFR) value given by inulin clearance. Repeatability, uncertainty and the beta-expectation limits were evaluated from pre-determined serum and urine pools of inulin. Agreement between the two methods was analyzed from 99 inulin clearances performed in renal transplant patients. Impact of the method of dosage on GFR evaluation was simulated according to the respective beta-expectations limits of each method. Overall, intra-assay coefficient of variability and relative bias were inferior to 5% and 10% for both methods. Contrary to the acid method, analytical performance of the enzymatic method was not influenced by the presence of glucose. The relative difference in GFR values obtained with the two methods in transplant patients was − 0.4 ± 10%. Simulations suggested that changes in inulin concentration attributable to analytical error could modify the value of GFR from − 12% to + 28%. In conclusion, while analytical performances are globally acceptable for both methods, they are not strictly equivalent. The impact on the determination of GFR, albeit limited, is not negligible and adds to other sources of inaccuracy. International standardization for the dosage of inulin is necessary. [less ▲]

Comparaison d'une méthode "acide" et enzymatique pour le dosage de l'inuline

in Néphrologie & Thérapeutique (2010, September), 6(5), 316

MDRD or CKD-EPI study equations for estimating prevalence of stage 3 CKD in epidemiological studies: which difference? Is this difference relevant?

in BMC Nephrology (2010), 11(8),

Background: Prevalence of stage 3 chronic kidney disease (CKD) is increasing according to the NHANES study. Prevalence has been calculated using the MDRD study equation for estimating glomerular ... [more ▼]

Background: Prevalence of stage 3 chronic kidney disease (CKD) is increasing according to the NHANES study. Prevalence has been calculated using the MDRD study equation for estimating glomerular filtration rate (GFR). Recently, a new estimator based on creatinine, the CKD-EPI equation, has been proposed which is presumed to better perform in normal GFR ranges. The aim of the study was to measure the difference in prevalence of stage 3 CKD in a population using either the MDRD or the CKD-EPI study equations. Methods: CKDscreening is organized in the Province of Liège, Belgium. On a voluntary basis, people aged between 45 and 75 years are invited to be screened. GFR is estimated by the MDRD study equation and by the "new" CKD-EPI equations. Results: The population screened consisted in 1992 people (47% of men). Mean serum creatinine was 0.86 ± 0.20 mg/dl. The prevalence of stage 3 CKD in this population using the MDRD or the CKD-EPI equations was 11.04 and 7.98%, respectively. The prevalence of stage 3 CKD is significantly higher with the MDRD study equation (p <0,0012). Conclusions: Prevalence of stage 3 CKDvaries strongly following the method used for estimating GFR, MDRD or CKDEPI study equations. Such discrepancies are of importance and must be confirmed and explained by additional studies using GFR measured with a reference method. [less ▲]

Allocation of ECD Kidneys Based on Donor GFR: The Choice of the Estimating Equation Matters

in American Journal of Transplantation (2010), 10