Relationship between creatinine and creatinine clearance with an enzymatic method

Abstract

 In the Schwartz calculation of creatinine clearance using height, serum creatinine concentration and coefficient k to estimate glomerular filtration rate. Creatinine concentration is assessed by Jaffe rate assay rather than the enzymatic method preferred in Japan. Objective: To determine k values for use with an enzymatic method. Methods: Urine of patients (N=172, age 2-21 yrs, males 99), was tested over exactly 24 h for creatinine clearance when examined for various kidney diseases between January, 2002 and July, 2007 (dialysis patients excluded). An enzymatic method, ACCURAS AUTO -CRE diagnosis kit (SHINO-TEST, Japan), was employed to test serum and urine. Measurements were analyzed using a Hitachi-7170S (Hitachi, Japan). Subjects were divided into three groups: 107 boys and girls, 2-12 yrs; 31 boys, 13-21 yrs; 34 girls, 13-21 yrs. Results: Mean total creatinine clearance=107.0±44.4ml/min/1.73m². The relations with L/Cre (X) and Ccr (Y) were: Y=0.3977X (r²=0.5802); Y=0.3857X (r²=0.4471) and Y=0.5271X (r²=0.681), respectively. They revealed a close correlation. Conclusion: The Schwartz formula can be used when creatinine concentration is measured by an enzymatic method. The k coefficients were 0.53 for boys aged 13-21 yrs, 0.40 for girls aged 13-21 yrs and 0.40 for boys and girls aged 2-12 yrs.