Comparison of GFR measurements assessed from single versus multiple samples

Area of Science:

• Nephrology
• Renal Physiology
• Diagnostic Testing

Background:

• Previous studies compared single-sample glomerular filtration rate (GFR) against multisample GFR, but not against an independent reference method.
• This study aimed to compare single and multisample GFR against a simultaneous, independent multisample GFR using a different indicator.

Purpose of the Study:

• To evaluate the reliability of single-sample GFR (ssGFR) compared to multisample GFR (msGFR).
• To compare ssGFR and msGFR using two different indicators, chromium-51 ((51)Cr)-EDTA and iohexol, against each other and an independent reference.

Main Methods:

• A diagnostic test study involving 95 studies in 60 patients and 20 healthy volunteers.
• GFR was measured using simultaneous (51)Cr-EDTA and iohexol injections, with blood samples collected over 4 hours.
• Single-sample GFR was calculated using the Jacobsson method at 3 and 4 hours, and compared with msGFR using Bland-Altman analysis.

Main Results:

• Limits of agreement for ssGFR at 3 and 4 hours were comparable to those for msGFR.
• Precision of ssGFR at 4 hours using (51)Cr-EDTA was superior to msGFR with the same indicator.
• ssGFR showed similar repeatability to msGFR in healthy participants and detected food-induced GFR changes more confidently.

Conclusions:

• Single-sample GFR is a reliable method for measuring GFR, comparable to multisample GFR.
• This reliability is particularly noted when GFR is above 60 mL/min.
• Further research is needed to interpret differences between markers without a definitive gold standard like inulin.