Derived GFR (dGFR) Values from Technetium-99m-MAG3 Data: A Comparison with the 24-Hour Creatinine Clearance

Abstract

Objective: Glomerular filtration can eliminate a substance only from the filtered fraction of the renal plasma flow. Since that fraction normally is 20%, ERPF agents clear from the kidneys about five times as fast as GFR agents. In most chronic renal diseases, the filtration fraction (GFR divided by ERPF) is largely unaffected, so the GFR can be estimated by dividing the ERPF by five. The aim of this study was to test this hypothesis.

Methods: ERPF determinations were made in 52 patients. The results were then divided by five to derive GFR values. Each patient had a 24-hr creatinine clearance test within three days of the ^99mTc MAG3 study. Patients with acute renal failure or transplant rejection were excluded from the protocol.

Results: There was a high degree of correlation between the 24-hr creatinine clearance and the derived GFR values (dGFR) obtained from the ^99mTc MAG3 data, r = 0.97, p < 0.05.

Conclusion: Reliable dGFR values can be easily calculated in most chronic renal states using ^99mTc MAG3 data; these derived values are well correlated to those obtained by the 24-hr creatinine clearance.