Monitoring renal function: A prospective study comparing camera-based technetium-99m mercaptoacetyltriglycine clearance and creatinine clearance

OBJECTIVES To determine the value and limitations of technetium-99m mercaptoacetyltriglycine (MAG3) clearance measurements obtained using a gamma camera (camera-based MAG3 clearance), a prospective study was conducted to evaluate the reproducibility of camera-based MAG3 clearance compared with that of conventional creatinine clearance. METHODS A total of 24 male patients with stable renal function were entered into the study. The mean age was 66.5 +/- 7.9 years, and the mean serum creatinine was 1.38 +/- 0.57 mg/dL. MAG3 renal scans and 24-hour creatinine clearance measurements were performed 11 +/- 8 days apart. A camera-based MAG3 clearance was obtained at each MAG3 scan; no blood samples were required. Bland-Altman plots were constructed to assist in data analysis. RESULTS The Pearson correlation for the first and second camera-based MAG3 clearances (mean 151 versus 158 mL/min/1.73 m(2), respectively) was 0.965 compared with 0.729 for the two creatinine clearance measurements (mean 62 versus 72 mL/min/1.73 m(2), respectively). Even with the omission of two outliers, the creatinine clearance would have to change by 58.2% compared with the baseline measurement before the clinician could be confident the change exceeded the error of measurement. In contrast, the change required for the camera-based MAG3 clearance was 30.8%. CONCLUSIONS The results of this study have demonstrated that MAG3 clearance obtained using a camera-based technique shows greater precision than the conventional creatinine clearance and is superior to the conventional creatinine clearance for monitoring changes in renal function.