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Iohexol plasma clearance for measuring glomerular filtration rate in clinical practice and research: a review. Part 1: How to measure glomerular filtration rate with iohexol?

View Article: PubMed Central - PubMed

ABSTRACT

While there is general agreement on the necessity to measure glomerular filtration rate (GFR) in many clinical situations, there is less agreement on the best method to achieve this purpose. As the gold standard method for GFR determination, urinary (or renal) clearance of inulin, fades into the background due to inconvenience and high cost, a diversity of filtration markers and protocols compete to replace it. In this review, we suggest that iohexol, a non-ionic contrast agent, is most suited to replace inulin as the marker of choice for GFR determination. Iohexol comes very close to fulfilling all requirements for an ideal GFR marker in terms of low extra-renal excretion, low protein binding and in being neither secreted nor reabsorbed by the kidney. In addition, iohexol is virtually non-toxic and carries a low cost. As iohexol is stable in plasma, administration and sample analysis can be separated in both space and time, allowing access to GFR determination across different settings. An external proficiency programme operated by Equalis AB, Sweden, exists for iohexol, facilitating interlaboratory comparison of results. Plasma clearance measurement is the protocol of choice as it combines a reliable GFR determination with convenience for the patient. Single-sample protocols dominate, but multiple-sample protocols may be more accurate in specific situations. In low GFRs one or more late samples should be included to improve accuracy. In patients with large oedema or ascites, urinary clearance protocols should be employed. In conclusion, plasma clearance of iohexol may well be the best candidate for a common GFR determination method.

No MeSH data available.


Related in: MedlinePlus

Elimination of iohexol from plasma after a single injection. Following a single injection, iohexol concentration in plasma falls as a result of both distribution and elimination. In a semi-logarithmic plot these phases can be illustrated by two lines, the slopes of which are proportional to the half-life of each phase.
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SFW070F1: Elimination of iohexol from plasma after a single injection. Following a single injection, iohexol concentration in plasma falls as a result of both distribution and elimination. In a semi-logarithmic plot these phases can be illustrated by two lines, the slopes of which are proportional to the half-life of each phase.

Mentions: Because of its physical characteristics (viscosity and density), iohexol is particularly suitable for plasma clearance measurement. After a bolus injection, plasma iohexol concentration will decrease constantly according to two different exponential curves (see Figure 1). The first rapid curve (fast component) corresponds to the volume of distribution, i.e. the extracellular volume [22–26]. The second curve (slow component) corresponds to the clearance of the marker by the kidney. There are several different methodologies to calculate GFR from the disappearance curves. The most precise method is to measure iohexol in both components, and to calculate the area under the curve which eventually allows GFR calculation [which corresponds to the dose of iohexol injected divided by the area under the curve (AUC)]. This method, named AUC in the current article, implies sampling of several plasma measurements at different time points. Iohexol should be sampled at very short intervals at the beginning (at 5, 10, 20, 30, 45, 60, 90 and 120 min after injection [52]), and thereafter every hour. This methodology is complex and costly, especially with necessary repeated samples during the first 2 h. For this reason, authors have proposed a mathematical correction for the first fast exponential curve. This method is frequently named as the slope-intercept method. Different mathematical corrections have been proposed [131, 133, 134, 135]. The impact of these different corrections on GFR results is probably relatively limited. The correction proposed by Brochner-Mortensen (BM) [116], initially developed for 51Cr-EDTA, is the most used in Europe:Fig. 1.


Iohexol plasma clearance for measuring glomerular filtration rate in clinical practice and research: a review. Part 1: How to measure glomerular filtration rate with iohexol?
Elimination of iohexol from plasma after a single injection. Following a single injection, iohexol concentration in plasma falls as a result of both distribution and elimination. In a semi-logarithmic plot these phases can be illustrated by two lines, the slopes of which are proportional to the half-life of each phase.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036902&req=5

SFW070F1: Elimination of iohexol from plasma after a single injection. Following a single injection, iohexol concentration in plasma falls as a result of both distribution and elimination. In a semi-logarithmic plot these phases can be illustrated by two lines, the slopes of which are proportional to the half-life of each phase.
Mentions: Because of its physical characteristics (viscosity and density), iohexol is particularly suitable for plasma clearance measurement. After a bolus injection, plasma iohexol concentration will decrease constantly according to two different exponential curves (see Figure 1). The first rapid curve (fast component) corresponds to the volume of distribution, i.e. the extracellular volume [22–26]. The second curve (slow component) corresponds to the clearance of the marker by the kidney. There are several different methodologies to calculate GFR from the disappearance curves. The most precise method is to measure iohexol in both components, and to calculate the area under the curve which eventually allows GFR calculation [which corresponds to the dose of iohexol injected divided by the area under the curve (AUC)]. This method, named AUC in the current article, implies sampling of several plasma measurements at different time points. Iohexol should be sampled at very short intervals at the beginning (at 5, 10, 20, 30, 45, 60, 90 and 120 min after injection [52]), and thereafter every hour. This methodology is complex and costly, especially with necessary repeated samples during the first 2 h. For this reason, authors have proposed a mathematical correction for the first fast exponential curve. This method is frequently named as the slope-intercept method. Different mathematical corrections have been proposed [131, 133, 134, 135]. The impact of these different corrections on GFR results is probably relatively limited. The correction proposed by Brochner-Mortensen (BM) [116], initially developed for 51Cr-EDTA, is the most used in Europe:Fig. 1.

View Article: PubMed Central - PubMed

ABSTRACT

While there is general agreement on the necessity to measure glomerular filtration rate (GFR) in many clinical situations, there is less agreement on the best method to achieve this purpose. As the gold standard method for GFR determination, urinary (or renal) clearance of inulin, fades into the background due to inconvenience and high cost, a diversity of filtration markers and protocols compete to replace it. In this review, we suggest that iohexol, a non-ionic contrast agent, is most suited to replace inulin as the marker of choice for GFR determination. Iohexol comes very close to fulfilling all requirements for an ideal GFR marker in terms of low extra-renal excretion, low protein binding and in being neither secreted nor reabsorbed by the kidney. In addition, iohexol is virtually non-toxic and carries a low cost. As iohexol is stable in plasma, administration and sample analysis can be separated in both space and time, allowing access to GFR determination across different settings. An external proficiency programme operated by Equalis AB, Sweden, exists for iohexol, facilitating interlaboratory comparison of results. Plasma clearance measurement is the protocol of choice as it combines a reliable GFR determination with convenience for the patient. Single-sample protocols dominate, but multiple-sample protocols may be more accurate in specific situations. In low GFRs one or more late samples should be included to improve accuracy. In patients with large oedema or ascites, urinary clearance protocols should be employed. In conclusion, plasma clearance of iohexol may well be the best candidate for a common GFR determination method.

No MeSH data available.


Related in: MedlinePlus