Glomerular filtration rate determined from a single plasma sample after intravenous iohexol injection: Is it reliable?

Flavio Gaspari, Elena Guerini, Norberto Perico, Lidia Mosconi, Piero Ruggenenti, Giuseppe Remuzzi

Research output: Contribution to journalArticlepeer-review


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 2, 4 h for clearances between 40 and 99 mL/min per 1.73 m2, and 3 h 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 radio-contrast injection does not represent a real advantage over the multiple-point method and may lead to unacceptable errors in GFR calculation.

Original languageEnglish
Pages (from-to)2689-2693
Number of pages5
JournalJournal of the American Society of Nephrology
Issue number12
Publication statusPublished - Dec 1996


  • GFR
  • Iohexol
  • Single injection
  • Single-point method

ASJC Scopus subject areas

  • Nephrology


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