title: Complex self-management interventions in chronic disease unravelled: a review of lessons learned from an individual patient data meta-analysis.
abstract: OBJECTIVE
  Meta-analyses using individual patient data (IPD) rather than aggregated data are increasingly applied to analyze sources of heterogeneity between trials and have only recently been applied to unravel multicomponent, complex interventions. This study reflects on methodological challenges encountered in two IPD meta-analyses on self-management interventions in patients with heart failure or chronic obstructive pulmonary disease.
  
  
  METHODS
  Critical reflection on prior IPD meta-analyses and discussion of literature.
  
  
  RESULTS
  Experience from two IPD meta-analyses illustrates methodological challenges. Despite close collaboration with principal investigators, assessing the effect of characteristics of complex interventions on the outcomes of trials is compromised by lack of sufficient details on intervention characteristics and limited data on fidelity and adherence. Furthermore, trials collected baseline variables in a highly diverse way, limiting the possibilities to study subgroups of patients in a consistent manner. Possible solutions are proposed based on lessons learnt from the methodological challenges.
  
  
  CONCLUSIONS
  Future researchers of complex interventions should pay considerable attention to the causal mechanism underlying the intervention and conducting process evaluations. Future researchers on IPD meta-analyses of complex interventions should carefully consider their own causal assumptions and availability of required data in eligible trials before undertaking such resource-intensive IPD meta-analysis.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, HP STR 6.131, P.O. Box 85500, Utrecht 3508 GA, The Netherlands; Faculty of Behavioural and Movement Sciences, VU University Amsterdam, Van der Boechorststraat 7, MF A-613, Amsterdam 1081 BT, The Netherlands. Electronic address: n.h.jonkman@vu.nl.
authors.forename: Nini H
authors.initials: NH
authors.lastname: Jonkman
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, HP STR 6.131, P.O. Box 85500, Utrecht 3508 GA, The Netherlands.
authors.forename: Rolf H H
authors.initials: RHH
authors.lastname: Groenwold
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, HP STR 6.131, P.O. Box 85500, Utrecht 3508 GA, The Netherlands.
authors.forename: Jaap C A
authors.initials: JCA
authors.lastname: Trappenburg
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, HP STR 6.131, P.O. Box 85500, Utrecht 3508 GA, The Netherlands.
authors.forename: Arno W
authors.initials: AW
authors.lastname: Hoes
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, HP STR 6.131, P.O. Box 85500, Utrecht 3508 GA, The Netherlands.
authors.forename: Marieke J
authors.initials: MJ
authors.lastname: Schuurmans
mesh_terms: D002908:Chronic Disease / Q000628:therapy*; D003625:Data Collection; D003627:Data Interpretation, Statistical; D006801:Humans; D015201:Meta-Analysis as Topic; D015999:Multivariate Analysis; D012648:Self Care / Q000379:methods
keywords: Chronic disease; Complex interventions; Individual patient data meta-analysis; Randomized trials; Self-care; Self-management; Subgroup analysis