Relationship of Formula Creatinine Clearance, Serum Creatinine and Blood Urea Nitrogen to 99mTc-MAG3 Clearance

Received 2/18/2002; revised 3/4/2002; accepted 3/8/2002. For correspondence or reprints contact: Nan-Tsing Chiu, M.D., Department of Nuclear Medicine, National Cheng Kung University Hospital, 138 Sheng-Li Road, Tainan 704, Taiwan. Tel: (886)6-2353535 ext. 2480, Fax: (886)6-2766609, E mail: [email protected] Background: We conducted this study to explore the correlation of formula creatinine clearance (FCcr), serum creatinine, blood urea nitrogen (BUN) to TcMAG3 clearance (CMAG3). Methods: Forty-seven adult patients with a wide range of renal function were included in this study. To assess glomerular filtration rate, FCcr was calculated from serum creatinine concentration, age and weight. CMAG3 was determined by one blood sample method. Linear regression was utilized to analyze correlation between CMAG3 and FCcr, serum creatinine or BUN. By using results of CMAG3 as a marker of renal dysfunction, the sensitivity and specificity of FCcr, serum creatinine and BUN were also calculated. Results: A good correlation was found between FCcr and CMAG3 (FCcr = 0.3469 CMAG3 + 1.6257, correlation coefficient (R) = 0.877, standard error of the estimate (SEE) = 17.64 ml/min). The correlation between serum creatinine and CMAG3 (serum creatinine = -0.009 CMAG3 + 3.2319, R = 0.633, SEE = 1.01) was not good. The correlation between BUN and CMAG3 (BUN = -0.0947 CMAG3 + 38.163, R = 0.698, SEE = 9.0) was not good, either. The sensitivities of FCcr, serum creatinine and BUN as markers for renal dysfunction were 86.2%, 45.8% and 50.0%, and specificities were 72.2%, 95.7% and 87.0%, respectively. Conclusions: This study showed a good correlation between FCcr and CMAG3, and poor correlation between serum creatinine, BUN to CMAG3. For detecting renal dysfunction, the sensitivity of FCcr was better than serum creatinine and BUN, but the specificity of FCcr was not good enough. CMAG3 could not be replaced by these three measurements for evaluating renal function.