title: Impact of being overweight on factor VIII dosing in children with haemophilia A.
abstract: BACKGROUND
  Treatment of haemophilia A (HA) requires infusions of factor VIII (FVIII) concentrates. The number of FVIII units infused to obtain a specific circulating FVIII level is calculated with the formula: [body weight (BW) (kg) × desired FVIII increase (%)]/2, with the assumption that each unit of FVIII infused per kg of BW increases the circulating FVIII level by 2%.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the impact of several morphometric parameters (BW, body mass index (BMI)-for-age, height), age and type of FVIII concentrate on FVIII recovery in children with HA.
  
  
  METHODS
  A total of 66 children aged between 10 and 18 with severe HA selected from six pharmacokinetic (PK) clinical trials using two recombinant FVIII concentrates were included in the analysis. Regression tree (RT) was used to identify predictors of FVIII recovery.
  
  
  RESULTS
  The median age was 14.5 years with a median FVIII recovery of 2.09 for all children. The median FVIII recovery was not significantly different between age groups. Two groups were created by RT: children with a BMI-for-age percentile <P95 (Median FVIII recovery: 1.94) and obese children with a BMI-for-age percentile ≥P95 (Median FVIII recovery: 2.65). The FVIII recovery was significantly different between these two groups (P < 0.001).
  
  
  CONCLUSIONS
  These results are consistent with previous studies conducted in adults with HA and confirm that the long-held and current practice of applying an arbitrary and universal recovery of two to the calculations of FVIII dosage should be abolished in both children and adults.
authors.affiliation: Institute of Health and Society (IRSS), Université catholique de Louvain, Brussels, Belgium.|Haemostasis and Thrombosis Unit, Division of Haematology, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Henrard
authors.affiliation: Haemostasis and Thrombosis Unit, Division of Haematology, Cliniques universitaires Saint-Luc, Brussels, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Hermans
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D003029:Coagulants / Q000493:pharmacokinetics / Q000627:therapeutic use*; D054796:Drug Dosage Calculations; D005169:Factor VIII / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006467:Hemophilia A / Q000188:drug therapy*; D006801:Humans; D015999:Multivariate Analysis; D050177:Overweight / Q000473:pathology*
chemical_list: D003029:Coagulants; C427184:recombinant factor VIII SQ; D005169:Factor VIII
keywords: adolescent; body mass index; children; factor VIII; haemophilia A; obesity