A scoping review of indirect comparison methods and applications using individual patient data.
Several indirect comparison methods, including network meta-analyses (NMAs), using individual patient data (IPD) have been developed to synthesize evidence from a network of trials. Although IPD indirect comparisons are published with increasing frequency in health care literature, there is no guidance on selecting the appropriate methodology and on reporting the methods and results.



In this paper we examine the methods and reporting of indirect comparison methods using IPD. We searched MEDLINE, Embase, the Cochrane Library, and CINAHL from inception until October 2014. We included published and unpublished studies reporting a method, application, or review of indirect comparisons using IPD and at least three interventions.



We identified 37 papers, including a total of 33 empirical networks. Of these, only 9 (27 %) IPD-NMAs reported the existence of a study protocol, whereas 3 (9 %) studies mentioned that protocols existed without providing a reference. The 33 empirical networks included 24 (73 %) IPD-NMAs and 9 (27 %) matching adjusted indirect comparisons (MAICs). Of the 21 (64 %) networks with at least one closed loop, 19 (90 %) were IPD-NMAs, 13 (68 %) of which evaluated the prerequisite consistency assumption, and only 5 (38 %) of the 13 IPD-NMAs used statistical approaches. The median number of trials included per network was 10 (IQR 4-19) (IPD-NMA: 15 [IQR 8-20]; MAIC: 2 [IQR 3-5]), and the median number of IPD trials included in a network was 3 (IQR 1-9) (IPD-NMA: 6 [IQR 2-11]; MAIC: 2 [IQR 1-2]). Half of the networks (17; 52 %) applied Bayesian hierarchical models (14 one-stage, 1 two-stage, 1 used IPD as an informative prior, 1 unclear-stage), including either IPD alone or with aggregated data (AD). Models for dichotomous and continuous outcomes were available (IPD alone or combined with AD), as were models for time-to-event data (IPD combined with AD).



One in three indirect comparison methods modeling IPD adjusted results from different trials to estimate effects as if they had come from the same, randomized, population. Key methodological and reporting elements (e.g., evaluation of consistency, existence of study protocol) were often missing from an indirect comparison paper.
Li Ka Shing Knowledge Institute, St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.
Areti Angeliki
AA
Veroniki
Li Ka Shing Knowledge Institute, St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.|Department of Geriatric Medicine, Faculty of Medicine, University of Toronto, 27 King's College Circle, Toronto, ON, M5S 1A1, Canada.
Sharon E
SE
Straus
Li Ka Shing Knowledge Institute, St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.|Institute of Health Policy, Management and Evaluation, University of Toronto, Health Sciences Building, 155 College Street, 4th floor, Toronto, ON, M5T 3M6, Canada.
Charlene
C
Soobiah
Li Ka Shing Knowledge Institute, St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.
Meghan J
MJ
Elliott
Li Ka Shing Knowledge Institute, St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada. triccoa@smh.ca.|Epidemiology Division, Dalla Lana School of Public Health, University of Toronto, 155 College Street, 6th floor, Toronto, ON, M5T 3M7, Canada. triccoa@smh.ca.
Andrea C
AC
Tricco
D035843:Biomedical Research / Q000379:methods*; D006753:Hospital Records / Q000706:statistics & numerical data*; D006801:Humans; D033181:Information Dissemination / Q000379:methods*; D015201:Meta-Analysis as Topic; D010355:Patient Identification Systems / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012107:Research Design; D058028:Research Report
Individual participant data; Knowledge synthesis; Multiple treatments meta-analysis; Network meta-analysis; Patient-level data; Research methods; Scoping review