title: Weight-for-age standard score - distribution and effect on in-hospital mortality: A retrospective analysis in pediatric cardiac surgery.
abstract: OBJECTIVE
  To study the distribution of weight for age standard score (Z score) in pediatric cardiac surgery and its effect on in-hospital mortality.
  
  
  BACKGROUND
  WHO recommends Standard Score (Z score) to quantify and describe anthropometric data. The distribution of weight for age Z score and its effect on mortality in congenital heart surgery has not been studied.
  
  
  METHODS
  All patients of younger than 5 years who underwent cardiac surgery from July 2007 to June 2013, under single surgical unit at our institute were enrolled. Z score for weight for age was calculated. Patients were classified according to Z score and mortality across the classes was compared. Discrimination and calibration of the for Z score model was assessed. Improvement in predictability of mortality after addition of Z score to Aristotle Comprehensive Complexity (ACC) score was analyzed.
  
  
  RESULTS
  The median Z score was -3.2 (Interquartile range -4.24 to -1.91] with weight (mean±SD) of 8.4 ± 3.38 kg. Overall mortality was 11.5%. 71% and 52.59% of patients had Z score < -2 and < -3 respectively. Lower Z score classes were associated with progressively increasing mortality. Z score as continuous variable was associated with O.R. of 0.622 (95% CI- 0.527 to 0.733, P < 0.0001) for in-hospital mortality and remained significant predictor even after adjusting for age, gender, bypass duration and ACC score. Addition of Z score to ACC score improved its predictability for in-hosptial mortality (δC - 0.0661 [95% CI - 0.017 to 0.0595, P = 0.0169], IDI- 3.83% [95% CI - 0.017 to 0.0595, P = 0.00042]).
  
  
  CONCLUSIONS
  Z scores were lower in our cohort and were associated with in-hospital mortality. Addition of Z score to ACC score significantly improves predictive ability for in-hospital mortality.
authors.affiliation: Department of Anesthesiology, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bengaluru, Karnataka, India.
authors.forename: Antony
authors.initials: A
authors.lastname: George
authors.forename: Pushpa
authors.initials: P
authors.lastname: Jagannath
authors.forename: Shreedhar S
authors.initials: SS
authors.lastname: Joshi
authors.forename: A M
authors.initials: AM
authors.lastname: Jagadeesh
mesh_terms: D000367:Age Factors; D001835:Body Weight; D006348:Cardiac Surgical Procedures; D002675:Child, Preschool; D005260:Female; D006330:Heart Defects, Congenital / Q000401:mortality* / Q000601:surgery*; D017052:Hospital Mortality; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007902:Length of Stay; D008297:Male; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors