title: Observational and clinical trial findings on the comparative effectiveness of diabetes drugs showed agreement.
abstract: OBJECTIVE
  This study compares an observational study of diabetes treatment effectiveness to randomized controlled trials to assess their convergent validity.
  
  
  METHODS
  Multivariate models were developed using observational data to describe change in hemoglobin A1c (HbA1c; % unit) and weight (kilograms) after addition of a second-line oral diabetes drug to metformin monotherapy. Randomized trials of these scenarios were systematically identified. The models were used to simulate each trial, and simulated and actual results were compared by linear regression and meta-analysis.
  
  
  RESULTS
  Thirty-two randomized trials of second-line diabetes oral therapy were identified. For all outcomes and drugs studied, simulation and actual results correlated (P < 0.001). There were no statistically significant differences between meta-analyzed randomized and simulated results for effect on HbA1c. For effect on weight, results were qualitatively comparable, but for sulfonylureas, the simulated weight gain was nominally greater than seen in the randomized controlled trials.
  
  
  CONCLUSIONS
  An observational study of diabetes drug effectiveness showed convergent validity with randomized data. This supports cautious use of the observational research to draw conclusions about drug effectiveness in populations not studied in clinical trials. This approach may be useful in other situations where observational and randomized data need integration.
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Weill Cornell Medical College, 525 E 68th Street, 20th Floor Baker Pavilion, New York, NY 10021, USA. Electronic address: jaf9052@nyp.org.
authors.forename: James H
authors.initials: JH
authors.lastname: Flory
authors.affiliation: Department of Public Health, Weill Cornell Medical College, 425 E 61st Street, 3rd Floor, Suite 301, New York, NY 10065, USA.
authors.forename: Alvin I
authors.initials: AI
authors.lastname: Mushlin
mesh_terms: D001835:Body Weight; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008687:Metformin / Q000627:therapeutic use; D008875:Middle Aged; D015999:Multivariate Analysis; D064887:Observational Studies as Topic; D016032:Randomized Controlled Trials as Topic; D013453:Sulfonylurea Compounds / Q000627:therapeutic use; D016896:Treatment Outcome; D015430:Weight Gain
chemical_list: D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D008687:Metformin; D013453:Sulfonylurea Compounds
keywords: Comparative effectiveness data; Diabetes; HbA1c; Pharmacoepidemiology; Validation; Weight