Summary of study limitations for studies reporting prevalence of DKA
| Reference and quality score* | Study design | Ascertainment of T1D | Response Rate | DKA definition (potential for misclassification) | Representativeness | Denominator | Likelihood of potential biases |
| Beck 2 01233 JBI Score: 7 | Clinic-based registry | Stratified data provided for patients with confirmed T1D† | Very good | Self-report, potential for misclassification | Patient treated by endocrinologists | All patients in registry during specific study time period | Information bias: yes (past events) Selection bias: possible |
| Butalia 2 01320 Butalia 2 01421 JBI Score: 8 | Linked database analysis | NS | NA (used linked database data) | Valid; based on hospitalisation | Unclear | Patients in the Diabetes, Hypertension and Cholesterol Centre database (two centres) | Information bias: low Selection bias: possible |
| Cengiz 2 01322 JBI Score: 7 | Clinic-based registry | Not explicitly described | NS | Likely (self-reported hospitalisation)‡ | Patients treated by endocrinologists | All patients meeting age and disease duration requirements during study time period | Information bias: yes (past events) Selection bias: possible |
| Laimer 2 01640 JBI Score: 9 | Clinic-based registry | NS | NA (used clinic-based patient data) | Standardised, likely low | Unclear | Unclear why this is such a small subset of the overall DPV database population | Information bias: low Selection bias: unclear |
| Miller 2 01536 JBI Score: 7 | Clinic-based registry | Not explicitly described | NS | Likely (self-report); only reported for prior 3 months | Patients all treated by endocrinologists§ | All patients in registry during study period who had DKA data from a web-based questionnaire | Information bias: possible (past events) Selection bias: possible |
| Simmons 2 01337 JBI Score: 7 | Clinic-based registry | Not explicitly described in this publication | Not stated in this publication | Likely (self-report) | Patients are all treated by endocrinologists, which may introduce some selection bias | Did not include patients with missing data on type of insulin administration or users of real-time CGM | Information bias: possible (past events) Selection bias: possible |
| Sparud-Lundin 2 00841 JBI Score: 3 | Clinic-based study | Not stated | 86% of potential participants were included; 79% longitudinally followed | Relied on pH value, could be misclassified. 11.5% of the DKA values were missing at the latest time point | Patients all treated at one paediatric diabetes clinic and then had to be treated at one ofsix6 adult clinics | Unclear, assumed to be age-specific patient groups (not person-time)¶ | Information bias: low Selection bias: possible |
| Trief 2 01429 JBI Score: 7 | Clinic-based registry | Not explicitly described | NS; this analysis only includes patients with PHQ-8 data¶ | Yes (self-reported hospitalisation)‡; only reported for prior 3 months | Patients all treated by endocrinologists | All patients in registry (meeting age and duration of T1D requirements) during study period who had PHQ-8 data | Information bias: possible (past events) Selection bias: possible |
| Weinstock 201311 JBI Score: 8 | Clinic-based registry | Not explicitly described | NS | Yes (self-reported hospitalisation) | Patients all treated by endocrinologists | All patients in registry (meeting age and duration of T1D requirements) during study period | Information bias: possible (past events) Selection bias: possible |
| Wong 2 01438 JBI Score: 7 | Clinic-based registry | Not explicitly described | NS | Yes (self-reported hospitalisation) | Patients all treated by endocrinologists | All patients in registry (meeting age and duration of T1D requirements) during specific study time period | Information bias: possible (past events) Selection bias: possible |
*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.
†Confirmation of T1D diagnosis was problematic for some adult-onset patients with incomplete clinical data; therefore, this group of patients may include some adults with T2D who were misdiagnosed with T1D.
‡The frequency of DKA occurrence reported by the clinics from medical record extraction was lower compared with patients’ self-report of DKA events.
↵§The authors mention that uninsured individuals are likely under-represented in the cohort and pump use may be higher than it is in the overall population of type 1 diabetes in the USA.
¶PHQ-8 is an eight-item questionnaire that was given at the 1-year data collection point to participants aged ≥18 years.
DKA , diabetic ketoacidosis; DPV , Diabetes-Patienten-Verlaufsdokumentation; JBI , Joanna Briggs Institute; CGM, continuous glucose monitoring; NA, not applicable; NS , not stated; PHQ-8, Patient Health Questionnaire-8 response; T1D, type 1 diabetes mellitus.