Performance of iohexol determination in serum and urine by HPLC: Validation, risk and uncertainty assessment

Abstract

Background: Determination of glomerular filtration rate plays an important role in nephrological practice. Iohexol is a reference marker for glomerular filtration rate determination. It is available and safe. The aim of this study was to develop a simple, efficient and easy to use analytical method for the quantification of iohexol in serum and urine by high performance liquid chromatography and to thoroughly validate this method. Methods: The HPLC method was inspired from the method published by Krutzen. The e.noval software V2.0 (Arlenda, Liège, Belgium) was used to compute all validation results. Results: The validation results indicate that the method will give accurate and reliable results for serum values ranging from 12.95 to 1295 μg/ml and for urine values ranging from 86.0 to 4144 μg/ml. In routine practice, iohexol concentrations found in plasma after injection range from 40 to 600 μg/ml. The expected urinary values are much wider. One should not hesitate to dilute urine samples to fit with the validated range over 5000 μg/ml. Conclusion: This is the first time that a reference method for the determination of GFR is validated with such a rigorous and thorough protocol. Contrary to other GFR markers, iohexol is now strongly validated from an analytical point of view.

Two Novel Equations to Estimate Kidney Function in Persons Aged 70 Years or Older

“…This analysis of the supernatant was done on an HPLC system with a diode-array detector (Hitachi, Mannheim, Germany) and a Chromolith performance HPLC column (RP-18e [100 × 4.6 mm], Merck, Darmstadt, Germany) and a Chromolith guard-column (RP-18e [5 × 4.6 mm], Merck) (24,25). Glomerular filtration rate was calculated with the clearance computed from the amount of the marker administered and the area under the receiver-operating characteristic curve of plasma concentration versus time.…”

How Measuring Glomerular Filtration Rate? Comparison of Reference Methods

“…Globally, the performance of 51 Cr-EDTA is good. Chantler, in 1969, showed that results of urinary clearance of 51 Cr-EDTA was within 5% of the results of inulin (Chantler et al, 1969). This excellent concordance between urinary clearances of 51 Cr-EDTA and inulin will be later confirmed by Froissart.…”

“…As we have shown, iohexol measurements by HPLC are sensitive, specific and reproducible (Back et al, 1988c;Farthing et al, 2005;Cavalier et al, 2008). The high performance of such dosage notably enables the use of iohexol low doses and the measurement on finger-prick samples (Krutzen et al, 1990;Niculescu-Duvaz et al, 2006;Mafham et al, 2007;Cavalier et al, 2008;Aurell, 1994). Iohexol measurement is also pretty stable at room temperature and at -20°C (Krutzen et al, 1984;O'Reilly et al, 1988).…”

“…Nevertheless, we do not recommend this technique to measure GFR in pregnant women even if authors seem to use it safely (Brochner-Mortensen, 1978;Medeiros et al, 2009;Durand et al, 2006). The dose of EDTA is 1000x lesser than the dose considered as safe (Chantler et al, 1969).…”

“…Only, Rehling described a higher extra-renal clearance at 8.4% (Rehling et al, 1995). Measurement of 51 Cr-EDTA by nuclear count is very precise and easy because 51 Cr-EDTA half time is long (27 days) (Chantler et al, 1969). The quantity of 51 Cr-EDTA injected is relatively small and therefore the irradiating dose received by the patient is very limited (absorbed dose from 0.011 to 0.0077 mSv according to the radioactive dose injected which is usually 7 MBq).…”