SERUM CREATININE, HEIGHT, AND WEIGHT DO NOT PREDICT GLOMERULAR-FILTRATION RATE IN CHILDREN WITH IDDM

OBJECTIVE - To assess the validity of two equations: K x height/serum creatinine (KL/Cr; K = 0. 55 for females 1-1 8 yr of age and 0. 7 for males 12 - 18 yr of age) and (140 - age) X weight/72 X creatinine (X 0 .85 for women; Cockroft-Gault) in estimating glomerular filtration rat e in children and adolescents with IDDM. RESEARCH DESIGN AND METHODS- From the records of the Children's Hospital Diabetes Clinic, we select ed 70 patients with GFR determined by Tc-99m-labeled DTPA plasma clear ance, stable renal function, and simultaneous measurements of height, weight, blood pressure, HbA1c, and plasma creatinine. We compared DTPA -GFR with estimated GFR from KL/Cr and Cockroft-Gault equations for th ree groups: all patients, patients with DTPA-GFR less-than-or-equal-to 140 ml . min-1 . 1.73 m-2, and patients with DTPA-GFR > 140 ml . min- 1 . 1. 73 m-2. RESULTS - For all patients, mean values for DTPA-GFR = 147 (95% confidence interval, 139-155), for KL/Cr = 118 (110-125), and for Cockroft-Gault = 84 ml . min-1 - 1.73 m-2 (78- 90). For patients with DTPA-GFR less-than-or-equal-to 140, DTPA-GFR = 123 (117-128), KL/ Cr = 110 (100-119), and Cockroft-Gault = 92 (82-102). For patients wit h DTPA-GFR > 140, DTPA-GFR = 167 (158-177), KL/Cr = 125 (114-136), and Cockroft-Gault = 77 (71-84). Linear regression analysis showed signif icant (P < 0.05) relationships for KL/Cr only in patients with DTPA-GF R less-than-or-equal-to 140 (r = 0.29), for Cockroft-Gault in all pati ents (r = -0.46), and for patients with DTPA-GFR less-than-or-equal-to 140 (r = -0.31). Determination of a revised K for use in KL/Cr from i ndividual calculations of K (DTPA-GFR x Cr/L) yielded an average value of 0. 70 (SD = 0. 11). With the use of K = 0. 7, the mean KL/Cr value for patients with DTPA-GFR less-than-or-equal-to 140 ml - min-1 - 1.7 3 m-2 was 125 +/- 27 (95% confidence interval, 115-135), compared with a DTPA-GFR value of 123 +/- 14 (95% confidence interval, 117-128). CO NCLUSIONS- KL/Cr and Cockroft-Gault do not accurately estimate DTPA pl asma clearance. We recommend the use of K equal to 0.70 when estimatin g GFR in children and adolescents with IDDM and DTPA-GFR less-than-or- equal-to 140 using KL/Cr and do not recommend the use of the KL/Cr (fo r patients with DTPA-GFR >140) or the Cockroft-Gault equation in this population.