Samenvatting
Background
Kidney function can be assessed by the measured glomerular filtration rate (mGFR) and effective renal plasma flow (ERPF) using the exogenous filtration markers 125I-iothalamate and 131I-hippuran. These markers are unfavorable due to the radioactive burden for patients, personnel and environment. We studied whether we could replace the measurement of these radiolabeled compounds (‘warm method’) with the measurement of their non-radioactive isotopologues (‘cold method’).
Methods
We determined in 220 participants mGFR and ERPF by both the warm (gamma counting) and cold (LC-MS/MS) method on the same serum, urine, and infusion solution samples. Agreement between the methods was evaluated using Passing-Bablok regression and Bland-Altman analysis. Accuracy criteria were that ≥ 80% of the warm and cold mGFR measurements were within ± 30% (P30) and ≥ 50% within ± 10% (P10). Precision of mGFR was assessed by the standard deviation (SD) of the bias and the intra-test coefficient of variation (CV%) of the measurement methods were determined.
Results
mGFR measurements showed a mean difference of 1.97% and no clinically relevant bias when comparing the warm and cold methods. mGFR was accurate with a P30 of 100%, and a P10 of 76%. The cold method was precise; SD was 8.04 mL/min, and the intra-test CV% was 3.01 ± 3.15%. The ERPF values showed a mean difference of 19.2% and a large constant and proportional bias. Radiochemical impurities, which influence the warm method, were found in the ¹³¹I-hippuran formulation, and these were the cause of the discrepancy between the two methods.
Conclusions
The cold method provides equivalent mGFR results compared to the warm method. The ERPF determined using the cold method is unaffected by radiochemical impurities which significantly affect the warm method.
Kidney function can be assessed by the measured glomerular filtration rate (mGFR) and effective renal plasma flow (ERPF) using the exogenous filtration markers 125I-iothalamate and 131I-hippuran. These markers are unfavorable due to the radioactive burden for patients, personnel and environment. We studied whether we could replace the measurement of these radiolabeled compounds (‘warm method’) with the measurement of their non-radioactive isotopologues (‘cold method’).
Methods
We determined in 220 participants mGFR and ERPF by both the warm (gamma counting) and cold (LC-MS/MS) method on the same serum, urine, and infusion solution samples. Agreement between the methods was evaluated using Passing-Bablok regression and Bland-Altman analysis. Accuracy criteria were that ≥ 80% of the warm and cold mGFR measurements were within ± 30% (P30) and ≥ 50% within ± 10% (P10). Precision of mGFR was assessed by the standard deviation (SD) of the bias and the intra-test coefficient of variation (CV%) of the measurement methods were determined.
Results
mGFR measurements showed a mean difference of 1.97% and no clinically relevant bias when comparing the warm and cold methods. mGFR was accurate with a P30 of 100%, and a P10 of 76%. The cold method was precise; SD was 8.04 mL/min, and the intra-test CV% was 3.01 ± 3.15%. The ERPF values showed a mean difference of 19.2% and a large constant and proportional bias. Radiochemical impurities, which influence the warm method, were found in the ¹³¹I-hippuran formulation, and these were the cause of the discrepancy between the two methods.
Conclusions
The cold method provides equivalent mGFR results compared to the warm method. The ERPF determined using the cold method is unaffected by radiochemical impurities which significantly affect the warm method.
| Originele taal-2 | English |
|---|---|
| Artikelnummer | sfaf293 |
| Aantal pagina's | 8 |
| Tijdschrift | Clinical Kidney Journal |
| Volume | 18 |
| Nummer van het tijdschrift | 10 |
| DOI's | |
| Status | Published - 23-sep.-2025 |