Evaluation of Renal Function: A Comparison Between Camera-Based Tc-99m MAG3 and 24-Hour Creatinine Clearances

OBJECTIVE: The 24-hour creatinine clearance is the standard clinical technique to measure renal function; however, this measurement is cumbersome and inconvenient for patients. We hypothesized that a camera-based Tc-99m mercaptoacetyltriglycine (MAG3) clearance obtained simultaneously with a standard MAG3 scan would correlate well with the 24-hour creatinine clearance and could serve as a simple marker of renal function. MATERIALS AND METHODS: Data were obtained from a retrospective analysis of 28 patients with varying degrees of renal dysfunction and 85 subjects evaluated for kidney donation. The MAG3 clearance was calculated using a camera-based technique without blood or urine sampling. The creatinine clearance was measured using the plasma creatinine and a 24-hour urine collection. The MAG3 and creatinine clearances were corrected for body surface area and values in normal subjects and patients were compared using paired T-test analysis. The linear association between the MAG3 and creatinine clearances was expressed by Pearson’s correlation coefficient. RESULTS: The mean MAG3 clearance in the potential renal donors was 321 95 ml/min (95% C.I. 171-546 ml/min), significantly higher than the mean creatinine clearance of 15251 ml/min (95% C.I. 79-278 ml/min, p<0.001). The mean MAG3 clearance in patients was 15370 ml/min (95% C.I. 32-316 ml/min) and was also significantly higher than the mean creatinine clearance of 7436 ml/min (95% C.I. 21138 ml/min, p<0.001). The ratio of the mean creatinine clearance to the mean MAG3 clearance was essentially the same for volunteers and patients, 0.47 and 0.48,