Comparison and correlation of measurements of glomerular filtration rates by Tc-99m DTPA and 24-hour creatinine clearance.

BACKGROUND: The measurement of 24-hour creatinine clearance (CCr) is most commonly used to estimate glomerular filtration rate (GFR). A new rapid method for determining GFR by radionuclide compound Tc-99m diethylenetriamine-pentaacetic acid (DTPA) has been developed and widely used in the last decade. The purpose of this study is to compare and correlate the measurements of GFR by the two method. METHODS: The present series included 6 normal volunteer outpatients and 49 hospitalized patients with various degrees of renal dysfunction who were studied at Taichung Veterans General Hospital from June 1985 to June 1986. All patients underwent both Tc-99m DTPA GFR and 24-hour CCr. Tc-99m DTPA computed GFR was calculated using the formula of Gates. RESULTS: The radionuclide computed GFR for each subject was compared with his or her 24-hour CCr. The correlation coefficient (r) was 0.89 with p < 0.001. The subjects were divided into two groups. Group A consisted of 6 normal volunteers and 14 patients with serum creatinine less than 1.4 mg/dl (creatinine: normal range 0.7 to 1.4 mg/dl). Group B consisted of 35 patients with serum creatinine greater than 1.4 mg/dl. Group B was further divided into Subgroup 1 with serum creatainine from 1.4 to 10 mg/dl, and Subgroup 2 with serum creatinine above 10 mg/dl. There was good correlation and less absolute error between DTPA-GFR and CCr in Group A and Subgroup 1. The results suggest that, when serum creatinine is less than 10 mg/dl, either DTPA or CCr is a good method for detection of GFR. CONCLUSIONS: DTPA-GFR measurement using this radionuclide technique has shown good correlation with CCr when serum creatinine is under 10 mg/dl. In patients with renal impairment and with serum creatinine above 10 mg/dl, neither examination is reliable. A more sensitive test to evaluate GFR in severe renal impairment is required for further investigation.