title: Patient-level compared with study-level meta-analyses demonstrate consistency of D-dimer as predictor of venous thromboembolic recurrences.
abstract: OBJECTIVE
  We compared the performance of aggregate data (AD)--based and individual patient data (IPD)-based meta-analyses to synthesize evidence on the ability of D-dimer to distinguish recurrence risk in patients with unprovoked venous thromboembolism (VTE) who stopped anticoagulation.
  
  
  METHODS
  We compared the results of the published AD-based rate ratio of VTE recurrence for positive vs. negative D-dimer, estimated by a mixed-effect Poisson model, with those of the IPD-based hazard ratio obtained by a Cox regression stratified by trial. We performed three additional analyses to investigate the methodological reasons for differences between the two approaches, comparing the IPD Cox regression with AD generated from IPD Poisson regression (to control for differences in population on study), AD time-to-event meta-analysis, and AD generated from IPD meta-regression.
  
  
  RESULTS
  Published analyses agreed in direction and statistical significance when estimating the prognostic value of D-dimer even if IPD estimates suggested a stronger effect. The additional analyses suggested that differences in study populations might explain this slight difference. Poor reporting in published studies precluded a true comparison of AD- and IPD-based assessments of heterogeneity sources.
  
  
  CONCLUSIONS
  AD and IPD meta-analyses yielded similar estimates of D-dimer effect to distinguish risk for recurrent VTE. The IPD approach was justified by the need to investigate sources of heterogeneity.
authors: Department of Clinical Epidemiology and Biostatistics and Department of Medicine, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada. marcucci.maura@gmail.com
authors: Maura
authors: M
authors: Marcucci
authors: Catrin Tudur
authors: CT
authors: Smith
authors: James D
authors: JD
authors: Douketis
authors: Alberto
authors: A
authors: Tosetto
authors: Trevor
authors: T
authors: Baglin
authors: Mary
authors: M
authors: Cushman
authors: Sabine
authors: S
authors: Eichinger
authors: Gualtiero
authors: G
authors: Palareti
authors: Daniela
authors: D
authors: Poli
authors: Robert Campbell
authors: RC
authors: Tait
authors: Alfonso
authors: A
authors: Iorio
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage; D015415:Biomarkers / Q000097:blood; D002986:Clinical Trials as Topic; D003627:Data Interpretation, Statistical; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D015201:Meta-Analysis as Topic; D011237:Predictive Value of Tests; D012008:Recurrence; D012307:Risk Factors; D054556:Venous Thromboembolism / Q000097:blood* / Q000188:drug therapy; D028761:Withholding Treatment
chemical_list: D000925:Anticoagulants; D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D