Reference serum creatinine levels determined by an enzymatic method in Japanese children: relationship to body length

Background It is necessary to set the standard serum creatinine (Cr) values for the medical care of pediatric chronic kidney disease patients. The estimated glomerular filtration rate (eGFR, ml/min/1.73 m 2 ) = κ × body length (cm)/serum Cr value (mg/dl) determined by the Jaffe method devised by Schwartz has been used clinically. However, enzymatic methods have recently been used to measure Cr instead of the Jaffe method, making it necessary to reevaluate the coefficient κ of the above equation. Following transformation of the above formula, the normal serum Cr level should be proportional to body length: normal serum Cr value (mg/dl) = k × body length (m). Methods Serum Cr values were measured by an enzymatic method in children who did not present with kidney disease or infectious disease, and the relationship between the body length and serum Cr level was determined by linear regression analysis. Results We found a regression equation capable of estimating the reference value of serum Cr from body length. In children aged 1–12 years, body length (m) × 0.30 yielded a value similar to the reference serum Cr level. Conclusion There have been no previous reports of the determination of reference serum Cr levels by enzymatic methods in Japanese children. Our formula will be applicable for screening of renal function in Japanese children.