title: Schwartz formula: is one k-coefficient adequate for all children?
abstract: OBJECTIVE
  Plasma-creatinine-based equations to estimate the glomerular filtration rate are recommended by several clinical guidelines. In 2009, Schwartz et al. adapted the traditional Schwartz equation to children and adolescents but did not find different k-coefficients between children and adolescents (k = 36.5 for all patients). We reevaluated the coefficient of the 2009-Schwartz formula according to sex and age in a pediatric population.
  
  
  METHODS
  We used linear mixed-effects models to reestimate the 2009-Schwartz k-coefficient in 360 consecutive French subjects aged 1 to 18 years referred to a single centre between July 2003 and July 2010 (965 measurements). We assessed the agreement between the estimated glomerular filtration rate obtained with the new formula (called Schwartz-Lyon) and the rate measured by inulin clearance. We then compared this agreement to the one between the measured glomerular filtration rate and 2009-Schwartz formula, first in the French then in a Swedish cohort.
  
  
  RESULTS
  In Schwartz-Lyon formula, k was estimated at 32.5 in boys <13 years and all girls and at 36.5 in boys aged ≥13 years. The performance of this formula was higher than that of 2009-Schwartz formula in children <13 years. This was first supported by a statistically significant reduction of the overestimation of the measured glomerular filtration rate in both cohorts, by better 10% and 30% accuracies, and by a better concordance correlation coefficient.
  
  
  CONCLUSIONS
  The performance and simplicity of Schwartz formula are strong arguments for its routine use in children and adolescents. The specific coefficient for children aged <13 years further improves this performance.
authors.affiliation: Centre de Référence des Maladies Rénales Rares, Service de Néphrologie et Rhumatologie Pédiatriques, Hospices Civils de Lyon, Lyon, France. vandreasouza@gmail.com
authors.forename: Vandrea Carla
authors.initials: VC
authors.lastname: De Souza
authors.forename: Muriel
authors.initials: M
authors.lastname: Rabilloud
authors.forename: Pierre
authors.initials: P
authors.lastname: Cochat
authors.forename: Luciano
authors.initials: L
authors.lastname: Selistre
authors.forename: Aoumeur
authors.initials: A
authors.lastname: Hadj-Aissa
authors.forename: Behrouz
authors.initials: B
authors.lastname: Kassai
authors.forename: Bruno
authors.initials: B
authors.lastname: Ranchin
authors.forename: Ulla
authors.initials: U
authors.lastname: Berg
authors.forename: Maria
authors.initials: M
authors.lastname: Herthelius
authors.forename: Laurence
authors.initials: L
authors.lastname: Dubourg
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D005260:Female; D005602:France; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D012189:Retrospective Studies; D013223:Statistics as Topic / Q000379:methods*; D013548:Sweden
chemical_list: D003404:Creatinine