Table 1.

Study Characteristics and Methods

First Author and Year of Publication	Location	Data Source	Disease Focus	Study Design	Methodology
Studies that define time of transfer based on last pediatric and first adult visits
Bollegala 201721	Ontario, Canada	Population-based health administrative data	Inflammatory bowel disease (IBD)	Retrospective cohort	“pre-transfer”: 2 years before the last pediatric visit “transfer of care”: time between last pediatric visit and first adult visit occurring at age ≥18 “post-transfer”: time from the first adult visit onward for 2 years
Hale 201722	England	Routine hospital administrative data	Diabetes	Retrospective cohort	“Successful transition” = any adult service contact within 6 months of last paediatric contact. “Successful retention” = first planned adult contact within 6 months of the last planned paediatric contact, and at least 2 further adult contacts within the next 2 years
Mannion 201623	United States	National commercial insurance administrative claims database	Juvenile idiopathic arthritis (JIA)	Retrospective cohort	The first adult visit was defined as the transfer point; this resulted in 3 distinct intervals: pediatric, transfer, and adult
Wisk 201524	United States	Harvard Pilgrim Health Care Claims Data	Children with chronic conditions and healthy children	Retrospective Cohort	Timing of transfer measured from 16 years to first adult-focused primary care provider visit Transfer date: date of first adult-focused primary care visit
Zhao 201825	Ontario, Canada	Population-based health administrative data	Inflammatory bowel disease (IBD)	Retrospective cohort	Transfer period: time between first adult gastroenterologist visit and the last pediatric gastroenterologist visit.
Studies that defined time of transfer based on age
Blinder 201526	United States	5 US State Medicaid databases	Sickle cell Disease	Retrospective cohort	18th birthday was defined as the age of transfer
Cohen 201627	Ontario, Canada	Population-based health administrative data	Chronic health conditions	Retrospective cohort	18th birthday was defined as the age of transfer
Dickerson 201228	United States	Administrative data from 25 children’s hospitals within the Pediatric Health Information System (PHIS),	Sickle cell disease	Retrospective cohort	18th birthday was defined as the age of transfer
Nakhla 200913	Ontario, Canada	Population-based health administrative data	Diabetes	Retrospective cohort	18th birthday was defined as the age of transfer
Reilly 201729	Sweden	Population-based Swedish Inpatient Register	Celiac Disease	Retrospective Cohort	Pre-transition age: 16–17 years Post-transition age:19–20 years
Shulman 201815	Ontario, Canada	Population-based health administrative data	Diabetes	Retrospective cohort	Pre-transition age: 15–17 years Transition-age: 17–19 years Early adulthood: 19–26 years (end of study)
Singh 201930	Wisconsin, United States	Medicaid Data	Sickle Cell Disease	Retrospective Cohort	Transition age: 19 years
Toulany 201931	Ontario, Canada	Population-based health administrative data	Mental illness	Retrospective cohort	Pre-transition: 12–16 years During transition: 17–18 years After transition: 19–26 years
Wijlaars 201832	England	Hospital Episode Statistics Admitted Patient Care data	Long-term conditions (LTCs) (defined using the International Classification of Diseases)	Cross-sectional study	Pre-transition (ages 10–15 years) and after transition (19–24 years)