Dear Mahesh, As any model the original equation of Schwartz is evolving over the years and as more data is gathered.
The original paper had only one k : Schwartz GJ, Haycock GB, Edelmann CM Jr, Spitzer A. A simple estimate of glomerular filtration rate in children derived from body length and plasma creatinine. Pediatrics 1976; 58:259263. Then it was extended to other age groups to account for the maturational changes: Schwartz GJ, Brion LP, Spitzer A. The use of plasma creatinine concentration for estimating glomerular filtration rate in infants, children, and adolescents. Pediatr Clin North Am 1987; 34:571590. Then other papers suggested different adjustment to the original formula... and to make it applicable for other age groups. Please also note that the original k are applicable only for the old/standard Jaffe method to measure serum creatinine. Newer methods require some adjustments. Newer formulas are now published using cystatin and other markers. Zappitelli M, Parvex P, Joseph L, et al. Derivation and validation of cystatin C-based prediction equations for GFR in children. Am J Kidney Dis 2006; 48:221230 (standard Schwartz formula may be misleading when we have renal impairment) New equations to estimate GFR in children with CKD. Schwartz GJ, Muñoz A, Schneider MF, Mak RH, Kaskel F, Warady BA, Furth SL. J Am Soc Nephrol. 2009 Mar;20(3):629-37. Epub 2009 Jan 21. Estimating and measuring glomerular filtration rate in children. Work DF, Schwartz GJ. Curr Opin Nephrol Hypertens. 2008 May;17(3):320-5. Review. The right formula will depend on the nature of your pediatric population you want to calculate CRCL for , the method used for serum creatinine and whether you have some renally impaired children or not. Hope this helps Samer -----Original Message----- From: [email protected] on behalf of Samtani, Mahesh [PRDUS] Sent: Tue 3/31/2009 16:09 To: [email protected] Subject: [NMusers] Schwartz formulae Dear NMusers, I am having difficulty with the Schwartz formulae for computing GFR in kids. Some references state that the formula gives GFR in mL/min while others say it is mL/min/1.73 m². Also the value of k varies between references. This is what I plan on using. Are these formulas in the right units with the correct constants. Please advise, Mahesh ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~* Schwartz formula: GFR (mL/min/1.73 m²) = k*Height(cm) / Serum Creatinine (mg/dL) k = 0.33 in Preterm Infants k = 0.45 in Term infants to 1 year old k = 0.55 for children aged 2 to 12 years k = 0.55 for girls 13 to 21 years, and k = 0.70 for boys 13 to 21 years GFR corrected for the child's actual BSA, which can be obtained using the DuBois and DuBois formula GFR corrected = [GFR * 1.73] / BSA The DuBois and DuBois formula: BSA (m²) = (Weight^0.425 x Height^0.725) x 0.007184 where the weight is in kilograms and the height is in centimeters. ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
