The single-plasma-sample iohexol clearance method for determining GFR resulted in unacceptable prediction errors (-22% to +40% in 25% of patients) compared to the multiple-point method.
Observational (n=686)
Does a single-plasma-sample method after iohexol injection provide reliable GFR estimation compared to the multiple-point clearance method in outpatients?
The single-plasma-sample method for determining GFR after iohexol injection may lead to unacceptable errors compared to the multiple-point method.
Effect estimate: r2 = 0.988
p-value: p=<0.05
The iohexol injection plasma clearance method is a good alternative to the inulin clearance method for determination of GFR, but requires multiple blood samples. To avoid this, methods have been developed which derive GFR from a formula that uses a single plasma concentration of the tracer and anthropometric data. The aim of this study was to evaluate whether a single plasma sample taken after iohexol injection allows reliable estimation of GFR. In this study, results of single-point determination were compared with those obtained by multiple-point plasma clearance. The GFR of 686 outpatients with different degrees of renal function were recalculated by use of the Jacobsson formula. The optimum time for sampling was found at 10 h after injection of the marker for clearances 100 mL/min per 1.73 m2. Results documented that for 75% of the patients, the simplified technique gave an error between -5% to +5% in the evaluation of GFR; for the remaining 25% of the patients, prediction error ranged from -22% to +40%. Furthermore, despite a highly significant correlation between multiple-point iohexol clearance (six plasma samples) and the single-point method (Y = 0.968X + 1.704, r2 = 0.988), the regression intercept was statistically different from 0 and the standard error of the slope estimate established that 95% confidence interval did not include 1.0 (the line of identity), thus indicating that the model can be rejected by the data at a significance level of 0.05. Thus the single-plasma-sample method to determine GFR after radiocontrast injection does not represent a real advantage over the multiple-point method and may lead to unacceptable errors in GFR calculation.
Gaspari et al. (Sun,) conducted a observational in Renal function evaluation (n=686). Single-plasma-sample iohexol clearance method vs. Multiple-point iohexol plasma clearance method was evaluated on Reliable estimation of GFR (prediction error) (r2 = 0.988, p=<0.05). The single-plasma-sample iohexol clearance method for determining GFR resulted in unacceptable prediction errors (-22% to +40% in 25% of patients) compared to the multiple-point method.