Abstract
BackgroundCurrent guidelines regarding plasma-sampling techniques for glomerular filtration rate (GFR) determination are inconsistent. Single-sample methods are commonly believed not to be precise enough to meet clinical demands. The present study compared the agreement between single- and dual- plasma sampling methods with a three-point plasma clearance of iohexol.MethodsA total of 46 healthy volunteers and 124 chronic kidney disease (CKD) patients with varying degrees of renal dysfunction received 5 ml iohexol (300 mgI/ml) i.v. and plasma samples were drawn at 2-, 3- and 4-h post-injection. Plasma-iodine concentrations were detected by high-performance liquid chromatography (HPLC).ResultsBias was similar among single-plasma sampling methods (SPSM) and dual-plasma sampling methods (DPSM). The best correlation was obtained from the 2- and 4-h DPSM (concordance correlation coefficient [CCC]: 0.9988) with none of the estimates differed by more than 30% from the reference GFR and only one (0.06%) estimate differed by more than 10% (P30, 100%; P10, 99.4%). SPSM using samples around 3- or 4-h demonstrated acceptable accuracy at a GFR level of ≥60 ml/min/1.73m2 (P30 = 100% and P10 > 75% for both measurements).Conclusion4-h SPSM is advantageous in clinical practice in subjects with GFR ≥ 60 ml/min/1.73m2. For patients with an expected GFR < 60 ml/min/1.73m2, a prolonged sampling time is more reliable.
Highlights
Current guidelines regarding plasma-sampling techniques for glomerular filtration rate (GFR) determination are inconsistent
The best correlation from the analyses carried out was obtained from GFR24, the 2- and 4-h blood sampling, with a correlation coefficient (CCC) of 0.9988, which indicates almost perfect agreement with the 3 pt. The 2- (iGFR)
Bias was very low and similar among dual-plasma sampling methods (DPSM)-GFRs and single-plasma sampling methods (SPSM)-GFRs, while the precision of GFR24 was significantly better with an interquartile range (IQR) of the difference of 1.52 ml/min/1.73m2
Summary
Current guidelines regarding plasma-sampling techniques for glomerular filtration rate (GFR) determination are inconsistent. Single-sample methods are commonly believed not to be precise enough to meet clinical demands. Multiple blood samples beyond 6 h post-injection are needed to calculate the area under the time-concentration curve (AUC), if maximal precision and accuracy of the measurements are sought [5, 6], which would be rather time-consuming and compromise recruitment and subject compliance. A growing need for simplification has led to the application of single-compartment models that need only two to three blood samples, which calculate AUC from the intercept and slope of the final slow disappearance curve. By the two-compartment correction introduced by Brochner-Mortensen [7], the slope-intercept method provides greater simplicity and sufficient accuracy to meet clinical demands
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