Tailoring the sampling time of single-sample GFR measurement according to expected renal function: a multisite audit

Area of Science:

• Nuclear Medicine
• Radiopharmacy
• Renal Physiology

Background:

• The 2018 British Nuclear Medicine Society (BNMS) guidelines for Glomerular Filtration Rate (GFR) assessment recommend a single-sample technique.
• Optimal sampling time is crucial but difficult to predict accurately based on expected renal function.
• This study evaluates the accuracy and flexibility of the recommended sampling times.

Purpose of the Study:

• To assess the optimality of the single-sample GFR technique recommended by the 2018 BNMS guidelines.
• To determine the error introduced by incorrect sample timing.
• To infer the flexibility of the sampling regime for accurate GFR measurement.

Main Methods:

• Analysis of 6328 patient GFR assessments across six hospitals.
• Comparison of single-sample (Fleming) GFR results with slope-intercept GFR results.
• Utilized a reference dataset of 777 studies with multiple samples (5 min to 8 h) for validation.

Main Results:

• Revised recommended single-sample times: 2-h for GFR >90 mL/min/1.73m², 3-h for 50-90 mL/min/1.73m², and 4-h for 30-50 mL/min/1.73m².
• Adherence to these recommendations maintains root mean square error ≤3.30 mL/min/1.73m².
• Demonstrated a wide range of acceptable sample times for accurate GFR results.

Conclusions:

• Multisite study confirms a broad window for acceptable sample times in single-sample GFR assessment.
• Modified recommended single-sample times are proposed based on study findings.
• A lookup table for reporting errors associated with mistimed samples has been developed.