title: Discordances originated by multiple meta-analyses on interventions for myocardial infarction: a systematic review.
abstract: OBJECTIVE
  To clarify the impact of multiple (covering the same population, intervention, control, and outcomes) systematic reviews (SRs) on interventions for myocardial infarction (MI).
  
  
  METHODS
  Clinical Evidence (BMJ Group) sections and related search strategies regarding MI were used to identify multiple SRs published between 1997 and 2007. Multiple SRs were classified as discordant if they featured conflicting results or interpretation of them.
  
  
  RESULTS
  Thirty-six SRs (23.5% of 153 on the treatment or prevention of MI) were classified as multiple and grouped in 16 clusters [ie, at least two SRs with the same PICO (population, condition/disease, intervention, control) and at least one common outcome] exploring angioplasty, angiotensin-converting enzyme inhibitors, anticoagulants, antiplatelets, β-blockers, and stents. Complete agreement on statistically significant differences between interventions was found in 7 of 10 clusters with a shared composite outcome. Agreement was reduced when single outcomes were considered. Despite substantial variation and limited agreement in reporting of major outcomes, SRs agreed in their conclusions on the superiority of either the intervention or control in 14 of 16 clusters. Sources of minor discrepancies were found in terms of study and outcome selection, subgroup analyses, and interpretation of findings.
  
  
  CONCLUSIONS
  Multiple SRs agreed in their qualitative conclusions but not on reporting and on analyses of hard outcomes. Discordance on significance of treatment effects was due to a combination of variation in design with inclusion of different studies and lack of precision for single hard outcomes compared with a composite outcome. Such inconsistencies among SRs could potentially slow the translation of SRs' results to clinical and public health decision making and suggest the need for a broader methodological and clinical agreement on their design.
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Università degli Studi di Firenze, viale Gaetano Pieraccini, 6, 50139, Firenze, Italia. Electronic address: ersilia.lucenteforte@unifi.it.
authors.forename: Ersilia
authors.initials: E
authors.lastname: Lucenteforte
authors.affiliation: Unità di Epidemiologia Clinica, IRCCS Istituto Ortopedico Galeazzi, via Riccardo Galeazzi, 4, 20161, Milano, Italia; Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, via Carlo Pascal, 36, 20133, Milano, Italia.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Moja
authors.affiliation: Unità di Epidemiologia Clinica, IRCCS Istituto Ortopedico Galeazzi, via Riccardo Galeazzi, 4, 20161, Milano, Italia.
authors.forename: Valentina
authors.initials: V
authors.lastname: Pecoraro
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, largo Brambilla, 3, 50134, Firenze, Italia.
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Conti
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università degli Studi di Firenze, viale Morgagni, 50, 50134, Italia.
authors.forename: Antonio
authors.initials: A
authors.lastname: Conti
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, largo Brambilla, 3, 50134, Firenze, Italia.
authors.forename: Elena
authors.initials: E
authors.lastname: Crudeli
authors.affiliation: Dipartimento di Scienze Cliniche "Luigi Sacco", Università degli Studi di Milano, via Giovan Battista Grassi, 74, 20157, Milano, Italia; Unità Operativa Complessa di Malattie Cardiovascolari, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, via Francesco Sforza, 28, 20122, Milano, Italia.
authors.forename: Alessio
authors.initials: A
authors.lastname: Galli
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, largo Brambilla, 3, 50134, Firenze, Italia.
authors.forename: Gian Franco
authors.initials: GF
authors.lastname: Gensini
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, largo Brambilla, 3, 50134, Firenze, Italia.
authors.forename: Martina
authors.initials: M
authors.lastname: Minnelli
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Università degli Studi di Firenze, viale Gaetano Pieraccini, 6, 50139, Firenze, Italia.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Mugelli
authors.affiliation: Laboratorio di Elettrofisiologia Cardiaca, Dipartimento di Cardiologia, Ospedale Luigi Sacco, via Giovan Battista Grassi, 74, 20157, Milano, Italia; Montreal General Hospital McGill University Montreal, Montreal, Canada.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Proietti
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, largo Brambilla, 3, 50134, Firenze, Italia.
authors.forename: Jonida
authors.initials: J
authors.lastname: Shtylla
authors.affiliation: Centro Cochrane Italiano, Università degli Studi di Modena e via del Pozzo 71, 41124, Reggio Emilia, Italia.
authors.forename: Roberto
authors.initials: R
authors.lastname: D'Amico
authors.affiliation: Centro Cochrane Italiano, Università degli Studi di Modena e via del Pozzo 71, 41124, Reggio Emilia, Italia; Dipartimento Epidemiologia, Servizio Sanitario Regionale del Lazio, via di Santa Costanza, 53, 00198, Roma, Italia.
authors.forename: Elena
authors.initials: E
authors.lastname: Parmelli
authors.affiliation: Dipartimento di Chirurgia e Medicina Traslazionale, Università degli Studi di Firenze, largo Brambilla, 3, 50134, Firenze, Italia.
authors.forename: Gianni
authors.initials: G
authors.lastname: Virgili
mesh_terms: D006801:Humans; D015201:Meta-Analysis as Topic; D009203:Myocardial Infarction / Q000534:rehabilitation*; D012196:Review Literature as Topic
keywords: Cardiovascular agents; Dissent and disputes; Evidence based medicine; Meta-analysis; Myocardial infarction; Policy making