Table 2

Quality of the Included Studies Assessed With the Cochrane Risk of Bias Tool12

Study, YearAdequate Sequence GenerationAllocation ConcealmentBlinding of Investigators and/or Outcome AssessorsComplete Outcome Data
Keyserling et al,23 2002YesYesNoYes
Lorig et al,26 2008YesYesaNoYes
Lorig et al,25 2009YesYesaNoYes
Dale et al,32 2009YesYesNoYes
Cade et al,31 2009YesbNocNocYes
Heisler et al,22 2010YesYesYesYes
Philis-Tsimikas et al,27 2011YesYesaNoaYes
Smith et al,34 2011YesYesNoYes
Long et al,24 2012YesYesYesYes
Gagliardino et al,37 2013YesaNocNocNoc
Siminerio et al,29 2013YesNoaNoYes
Thom et al,30 2013YesYesNoaYes
Chan et al,36 2014YesYesNocYes
Simmons et al,33 2015YesYesYesYes
Safford et al,28 2015YesYesNoYes
Ayala et al,21 2015YesNocNocYes
McGowan,35 2015YesYesNoYes
  • Notes: Yes indicates low risk of bias; No indicates high risk of bias. Selective outcome reporting risk was considered minimal as we selected only studies that reported hemoglobin A1c level as the outcome. No other major biases were noted in the included studies. None of the trials blinded participants.

  • a Author response to information requests.

  • b Likely low risk of bias but no details on sequence generation available from article and author.

  • c Not reported or no response from author.