Iohexol-measured glomerular filtration rate in children and adolescents with chronic kidney disease: a pilot study comparing venous and finger stick methods
Measurement of glomerular filtration rate by iohexol disappearance (iGFR) has become a gold standard in the pediatric chronic kidney disease (CKD) population. The need for serial phlebotomy can be difficult and minimizing venipunctures would be beneficial. Furthermore, finger stick collection for dried blood spot (DBS) may be more tolerable in the pediatric population, and equivalence between these two methods may further simplify the process.
This was a cross-sectional study in children and adolescents 1 to 21 years with stages I–IV CKD. Iohexol was infused and blood drawn 10, 30, 120, and 300 min later. Blood spots on filter paper were collected by finger stick after each of the latter two blood draws. The rate of iohexol plasma disappearance was used to calculate GFR. Pearson’s correlation coefficient and bias, Students t test, and Bland-Altman graphical representations were used to compare methods.
Forty-one patients were recruited. The mean creatinine was 1.13 mg/dL (SD 0.45), the mean 4-point iGFR was 73.2 ml/min/1.73m2 (SD 27.5) and the mean 2-point iGFR was 75.6 ml/min/1.73m2 (SD 27.3). Correlation between 2-point and 4-point venous GFR was r = 0.97; p < 0.001. The correlation between the DBS and the 2-point venous GFR was r = 0.95; p < 0.001, with no significant bias. Ninety-four percent of the 2-point GFR’s were within 10% of the 4-point GFR’s and 80% of DBS-GFRs were within 10% of the 2-point GFR’s.
The 2-point iGFR was highly correlated and agreed well with the 4-point iGFR. The same was true for the DBS method and the 2-point venous method. DBS sampling by finger stick sampling at 2 time points after iohexol infusion gave an acceptably accurate measurement of GFR.
KeywordsPediatrics Iohexol Glomerular filtration rate Chronic kidney disease Dried blood spot
We would like to acknowledge Ms. Paula Maier for her invaluable assistance with data management.
There were three sites that contributed subjects to the study. The University of New Mexico site was supported by an intramural grant awarded to AS by the UNM Department of Pediatrics and a CTSC grant (UL1TR001449). The University of Rochester site and all the biochemical assays were supported by funds for the Central Biochemistry Laboratory of the CKiD consortium (U01-DK82194). CW receives additional funding from the CKiD consortium (U01-DK066143).
Compliance with ethical standards
The study was approved by the Institutional Review Boards of each of the participating centers. Informed consent was obtained from all participants in the study.
Conflicts of interest
The authors declare that they have no conflicts of interest. Preliminary results were presented in abstract form at the 16th Congress of the International Pediatric Nephrology Association, September 2013, in Shanghai, China.
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