# Comparison of plasma clearance of [51Cr]CrEDTA based on three, two and single samples to measure the glomerular filtration rate in patients with solid tumors: a prospective cross-sectional analysis

## TL;DR

This study compares different methods to measure kidney function in cancer patients using [51Cr]CrEDTA, finding that fewer blood samples can be sufficient for certain patients.

## Contribution

The study provides evidence that two-sample and single-sample methods can reliably measure GFR in cancer patients under specific conditions.

## Key findings

- High agreement was found between two-sample (46-GFR) and three-sample (246-GFR) methods for measuring GFR.
- Single-sample methods are suitable for non-obese patients with normal GFR.
- All methods showed adequate precision and accuracy, except for subgroups with extreme BMI or GFR.

## Abstract

•EDTA clearance can be used to measure GFR in patients with solid tumors.•Precise GFR assessment is crucial to optimize therapy and minimize side effects.•There is a high agreement between two (46GFR) and three-time samples (246GFR).•Single-sample tests may be adopted for non-obese patients with expected normal GFR.

EDTA clearance can be used to measure GFR in patients with solid tumors.

Precise GFR assessment is crucial to optimize therapy and minimize side effects.

There is a high agreement between two (46GFR) and three-time samples (246GFR).

Single-sample tests may be adopted for non-obese patients with expected normal GFR.

[51Cr]CrEDTA is used to measure the Glomerular Filtration Rate (GFR) in different clinical conditions. However, there is no consensus on the ideal number of blood samples to be taken and at what time points to measure its clearance. This study aimed to compare Slope Intercept (SI) and Single-Sample (SS) methods for measuring GFR in patients with solid tumors, stratified by age, GFR, and Body Mass Index (BMI).

1,174 patients with cancer were enrolled in this prospective study. GFR was calculated by the SI method using blood samples drawn 2-, 4-, and 6-hours after [51Cr]CrEDTA injection (246-GFR). GFR was also measured using the SI method with samples at 2 and 4 hours (24-GFR) and at 4 and 6 hours (46-GFR), and SS methods according to Groth (4Gr-GFR) and Fleming (4Fl-GFR). Statistical analysis was performed to assess the accuracy, precision, and bias of the methods.

Mean 246-GFR was 79.2 ± 21.9 mL/min/1.73 m2. ANOVA indicated a significant difference between 4Gr-GFR and the reference 246-GFR. Bias was lower than 5 mL/min/1.73 m2 for all methods, except for SS methods in subgroups BMI > 40 kg/m2; GFR > 105 or < 45. Precision was adequate and accuracy of 30 % was above 98% for all methods, except for SS methods in subgroup GFR < 45.

46-GFR and 246-GFR have high agreement and may be used to evaluate kidney function in patients with solid tumors. Single-sample methods can be adopted in specific situations, for non-obese patients with expected normal GFR.