Iohexol plasma clearance simplified by dried blood spot testing

Area of Science:

• Nephrology
• Clinical Chemistry
• Biomedical Diagnostics

Background:

• Estimating renal function relies on inaccurate formulas or impractical gold-standard methods.
• Plasma clearance of iohexol is a reliable but complex gold-standard for measuring renal function.
• A simplified method for assessing renal function is needed for broader clinical application.

Purpose of the Study:

• To simplify the gold-standard plasma clearance of iohexol using dried blood spot (DBS) testing.
• To validate the accuracy and precision of a novel DBS method for renal function assessment.
• To compare the performance of DBS testing against established plasma analysis techniques.

Main Methods:

• In vitro and in vivo studies were conducted to compare glomerular filtration rate (GFR) assessed by DBS and reference plasma analysis.
• Non-volumetric and volumetric DBS methods were tested for agreement with the reference technique.
• Clinical validation involved 203 patients, evaluating agreement using concordance correlation coefficient (CCC) and total deviation index (TDI).

Main Results:

• Non-volumetric DBS showed insufficient agreement (TDI = 26.0%).
• Volumetric DBS with iopamidol as an internal standard achieved acceptable agreement (TDI = 9.0%) in vitro.
• In vivo validation demonstrated acceptable agreement for the definitive DBS method (TDI = 9.5%) compared to plasma analysis.

Conclusions:

• A simplified dried blood spot (DBS) method for iohexol plasma clearance accurately measures renal function.
• The DBS method maintains accuracy and precision comparable to the reference plasma analysis technique.
• This simplified approach can enhance the accessibility of reliable renal function testing for the medical community.