To determine disease control, we gathered data and laboratory test results from the electronic medical records for the year preceding the final visit at the New Children’s Hospital. The final visit was specified as the outpatient appointment where the clinician made a formal referral to the respective adult health service. We divided participants into one of three categories according to the condition for which they were recruited: (1) good disease control and/or adherence; (2) some evidence of concern; and (3) poor disease control and/or adherence or more severe condition (see study protocol for further details).19 (link) Where appropriate, we used published cut-offs for disease control. For adolescents with diabetes, a mean glycosylated haemoglobin (the mean of all measurements across the year preceding transfer of care) ≤53 mmol/mol was categorised as good control/adherence, 54–69 mmol/mol was considered evidence of some concern, while ≥70 mmol/mol was classified as having poor control/adherence. For adolescents with rheumatic disease, the 10-joint Juvenile Arthritis Disease Activity Score was completed. For those with oligoarthritis, cut-off points of ≤0.5 (good), 0.6–2.8 (some concern) and >2.8 (poor) were used, while for those with polyarthritis, the cut-off points were ≤0.7, 0.8–4 and >4, as previously applied.19–21 (link) For adolescents with IBD, good control/adherence required minimal pain (Visual Analogue Scale, VAS 1–2), at least 80% of faecal calprotectin results <100 µg/g and always <300 µg/g, medication unchanged or reduced, and no inpatient care; indicators of some evidence of concern were VAS 3–5, <80% of faecal calprotectin results within target range or exceeded 300 µg/g even once, but no significant medication changes nor inpatient care; and for poor control/adherence any of the following: VAS ≥6, significant changes in medication, need for corticosteroids and/or commencement of biological medication or an episode of inpatient care. For rare conditions without standard criteria of disease control and/or adherence, experienced clinicians subjectively categorised participants according to their symptoms, clinical and laboratory findings, need for inpatient care and changes in medication. MK first reviewed medical records of every participant, of whom 28 (11%) were difficult to categorise. For these 28 adolescents, SK made an independent assessment of disease control. Six adolescents were categorised differently, and the final grading was based on a consensus between the two reviewers. For some analyses, we combined the three smallest subspecialties (neurology, cardiology and nephrology/organ transplant) into ‘others’.