title: A model-based approach to sample size estimation in recent onset type 1 diabetes.
abstract: The area under the curve C-peptide following a 2-h mixed meal tolerance test from 498 individuals enrolled on five prior TrialNet studies of recent onset type 1 diabetes from baseline to 12 months after enrolment were modelled to produce estimates of its rate of loss and variance.
  
  
  
  Age at diagnosis and baseline C-peptide were found to be significant predictors, and adjusting for these in an ANCOVA resulted in estimates with lower variance.
  
  
  
  Using these results as planning parameters for new studies results in a nearly 50% reduction in the target sample size. The modelling also produces an expected C-peptide that can be used in observed versus expected calculations to estimate the presumption of benefit in ongoing trials. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Health Informatics Institute, University of South Florida, Tampa, FL, USA.
authors.forename: Brian N
authors.initials: BN
authors.lastname: Bundy
authors.affiliation: Health Informatics Institute, University of South Florida, Tampa, FL, USA. jpkrischer@epi.usf.edu.
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Krischer
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D019540:Area Under Curve; D015415:Biomarkers / Q000097:blood*; D002096:C-Peptide / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011379:Prognosis; D018401:Sample Size; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002096:C-Peptide
keywords: C-peptide; clinical trial; type 1 diabetes