Single-sample methods to measure GFR with technetium-99m-DTPA

Area of Science:

• Nephrology
• Medical Diagnostics
• Radiopharmacology

Background:

• Glomerular filtration rate (GFR) measurement is crucial for assessing kidney function.
• Numerous single-sample methods aim to simplify GFR estimation.
• The clinical accuracy of these simplified methods remains uncertain.

Purpose of the Study:

• To evaluate the relative accuracy of various single-sample GFR estimation methods.
• To compare these methods against a gold standard plasma clearance technique.
• To determine the best performing single-sample method for clinical use.

Main Methods:

• Fifty-four GFR studies using 99mTc-DTPA were conducted on 37 adult patients.
• Compared plasma clearance (three-sample) with multiple single-sample methods (Christensen and Groth, Constable, Dakubu, Groth and Aasted, Jacobsson, Morgan, Russell, Tauxe).
• Analyzed performance based on GFR levels: > or = 30 ml/min and < 30 ml/min.

Main Results:

• At GFR >= 30 ml/min, all single-sample methods correlated well with plasma clearance, with Groth 4-hr method showing the lowest absolute and percent differences.
• At GFR < 30 ml/min, most single-sample methods performed poorly.
• The Groth and Aasted 4-hr method demonstrated the best accuracy in the severe renal failure group (GFR < 30 ml/min).

Conclusions:

• Single-sample GFR estimation methods may be unreliable in advanced renal failure.
• The Groth and Aasted 4-hr plasma sample method provides the most consistent accuracy across GFR ranges.
• While acceptable at higher GFRs, the reliability of most single-sample methods diminishes significantly in severe kidney disease.