title: Contact frequency determines outcome of basal insulin initiation trials in type 2 diabetes.
abstract: OBJECTIVE
  The aim of the present study was to investigate whether predetermined contact frequency with the study team and endpoint insulin dose are associated with study outcomes in basal insulin initiation trials in type 2 diabetes.
  
  
  METHODS
  A systematic Medline search was performed. Using data from the selected studies, contact frequency was plotted against HbA(1c) reduction and endpoint insulin dose. The importance of face-to-face vs telephone contact was also analysed. Insulin dose was plotted against HbA(1c) reduction, hypoglycaemia rate and weight gain. To investigate non-specific study effects, the relationship between contact frequency and HbA(1c) was also assessed in dipeptidyl peptidase-4 (DPP-4) inhibitor trials.
  
  
  RESULTS
  The reduction in HbA(1c) was highly correlated with contact frequency and endpoint insulin dose (r (2) = 0.751, p < 0.001 and r (2) = 0.433, p = 0.008, respectively). However, after adjusting for contact frequency, the relationship between insulin dose and HbA(1c) reduction was no longer significant (p = 0.270). The frequency of both clinical and telephone contacts were independent predictors of HbA(1c) improvement (p = 0.010 and p < 0.001, respectively). We found no dose-response relationship between end-of-study insulin dose and hypoglycaemia or weight gain. In DPP-4 inhibitor studies, contact frequency was not positively associated with HbA(1c).
  
  
  CONCLUSIONS
  The frequency of contact with the study team is highly correlated with the improvement in HbA(1c) achieved in basal insulin initiation trials in type 2 diabetic patients. This has important implications for trial design and interpretation, as well as for clinical care.
authors.affiliation: Department of Internal Medicine, Academic Medical Centre, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands. s.g.swinnen@amc.uva.nl.
authors.forename: S G H A
authors.initials: SGHA
authors.lastname: Swinnen
authors.affiliation: Department of Internal Medicine, Academic Medical Centre, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: DeVries
mesh_terms: D003142:Communication; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy* / Q000523:psychology; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D007328:Insulin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000069057:Insulin Detemir; D000069036:Insulin Glargine; D049528:Insulin, Long-Acting; D011369:Professional-Patient Relations; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome
chemical_list: D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D007328:Insulin; D000069057:Insulin Detemir; D000069036:Insulin Glargine; D049528:Insulin, Long-Acting