Table 1

Summary of study limitations for studies reporting incidence rate of DKA

Reference and quality score*Study designAscertainment of T1DResponse rateDKA definition (potential for misclassification)RepresentativenessDenominatorLikelihood of potential biases
Bohn 2 01527
JBI Score: 9
Clinic-based registryNSNA (clinic-based patient data)Standardised, likely lowUnclear; patients are all receiving ‘routine care’Total population with physical activity data in the DPVInformation bias: low Selection bias: unclear
Bryden 2 00328
JBI Score: 7
Longitudinal single-centre cohortNS89% (initially), with 87 of the 113 patients included at follow-upAll cases were based on hospitalisation, likely lowUnclear; patients from one specialist care clinic. Only data for patients with recurrent DKA admissions were reported.All follow-up person-time in the cohortInformation bias: low Selection bias: possible
Garg 2 00435
JBI Score: 1
Clinic-based single-centre registryNSNA (single-centre medical record data)Authors state use of definition from the DCCT Group (unclear potential)†Unclear; patients all treated at one specialty diabetes clinicUnclear; 515 patients on whom they pulled dataInformation bias: low
Selection bias: possible
Janez 201239
JBI Score: 0
Clinic-based single-centre registryNSNA (single-centre registry/database data)NS; misclassification potential unclear; data from medical records (not self-report)Unclear; patients are all treated at one specialty diabetes clinicUnclear; 184 patients on whom they pulled dataInformation bias: low
Selection bias: possible
Lebenthal 201223
JBI Score: 6
Clinic-based registryNSNA (clinic-based patient data)Standardised, likely lowUnclear; patients are all from one clinical centreUnclearInformation bias: low (but missing data)
Selection bias: unclear
Li
201442
JBI Score: 6
Longitudinal assessment of patients referred from 16 tertiary care hospitals in one provinceNSNA (patient medical records)Standardised/criteria-based definition, but data on DKA came from questionnaires (unclear potential)Unclear; patients are all from tertiary hospitals in one Chinese provinceNS; likely the entire study populationInformation bias: unclear
Selection bias: unclear
Nathan 200934
JBI Score: 7
DCCT/EDIC (initially an RCT; converted almost all patients to a cohort study design); EDC is a cohort studyNS for either DCCT/EDIC or EDCNS for DCCT, but 96% of trial participants agreed to participate in EDIC
NS for EDC
NS for either cohort. The DCCT/EDIC has both self-reported and clinic-measured variables (method of DKA assessment not stated); unclear potentialInitial cohort for DCCT/EDIC was selected for an RCT, increasing likelihood that patients may not reflect the broader T1D population. For EDC, authors state participants were representative of T1D population of Allegheny County, PAUnclearInformation bias: low
Selection bias: low
Shalitin 2 01243
JBI Score: 6
Tertiary care university hospital-based studyNSNA (single-centre patient medical records)Highly specific definition based on medical records; likely lowUnclear; patients were treated at a specialised tertiary care centreUnclear, but authors state there was up to 7 years of follow-up data on patients after CSII initiationInformation bias: low
Selection bias: low
  • *Quality score is based on the total number of ‘Yes’ responses on the JBI Quality Assessment tool for each study. Potential quality scores range from a low of 0 to a high of 9. In this paper, for the purposes of ease of discussion, a descriptive quality rating of ‘high’ was given to studies with eight or more Yes responses, and a descriptive quality rating of ‘low’ was given to studies with three or fewer ‘Yes’ responses. Studies with more than three and fewer than eight ‘Yes’ responses were described as ‘moderate’ quality.

  • †The study authors cite this source: N Engl J Med. 1993 Sep 30;329(14):977–86; however, on review, the source did not describe definition of DKA in the DCCT, nor did a high-level internet search.

  • DCCT , Diabetes Control and Complications Trial; DKA , diabetic ketoacidosis; DPV , Diabetes-Patienten-Verlaufsdokumentation; EDC , Epidemiology of Diabetes Complications; EDIC , Epidemiology of Diabetes Interventions and Complications; JBI , Joanne Briggs Institute; CSII, continuous subcutaneous insulin infusion; NA, not applicable; NS , not stated; PA , Pennsylvania; RCT , randomised controlled trial; T1D, type 1 diabetes mellitus; yr , year.