title: Towards the harmonization of outcome measures in children with mitochondrial disorders.
abstract: OBJECTIVE
  A clinical trial is only as reliable as its outcomes, therefore the careful and systematic selection of outcome measures is extremely important. Currently, the selection of outcome measures for clinical trials designed to evaluate new drugs in patients with mitochondrial disorders is inefficient and has not been addressed systematically. Given that meaningful data can be obtained only from trials in which outcomes are assessed using valid instruments, one should first focus on the validation of a set of selected instruments in the target population. The aim of this review is to systematically select a 'toolbox' of robust outcome measures that are relevant to all patients.
  
  
  METHODS
  Using an extensive search of published literature, we systematically compiled a toolbox with outcome measures based on a primary search for possible instruments Subsequently, we reduced this toolbox using strict criteria that were adapted from the United States Food and Drug Administration.
  
  
  RESULTS
  A toolbox with clinically relevant and psychometrically robust instruments for performing clinical research in children with mitochondrial disorders was compiled.
  
  
  CONCLUSIONS
  In coming years, more experience using these outcome measures in children with various mitochondrial disease phenotypes must be obtained before reliable conclusions regarding the validity of these instruments can be drawn.
authors.affiliation: Department of Paediatrics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Mitochondrial Disorders, Geert Grooteplein 10, Nijmegen, the Netherlands. S.Koene@cukz.umcn.nl
authors.forename: Saskia
authors.initials: S
authors.lastname: Koene
authors.forename: Merel
authors.initials: M
authors.lastname: Jansen
authors.forename: Chris M
authors.initials: CM
authors.lastname: Verhaak
authors.forename: Remco L A
authors.initials: RL
authors.lastname: De Vrueh
authors.forename: Imelda J M
authors.initials: IJ
authors.lastname: De Groot
authors.forename: Jan A M
authors.initials: JA
authors.lastname: Smeitink
mesh_terms: D002648:Child; D006801:Humans; D028361:Mitochondrial Diseases / Q000628:therapy*; D017063:Outcome Assessment, Health Care / Q000592:standards*; D011594:Psychometrics / Q000295:instrumentation*