Table 1

Summary of assessment measures to be completed at each time point

Measure	Data collected	Informant/source	Baseline	12 months	24 months
Demographics/background	Caregiver: age, gender, education, occupation, sexual orientation, ethnicity and relationship to child. CYP: age, sex assigned at birth, ethnicity, age at referral and background to referral.	P	×	×	×
Gender identity
Parent Questionnaire	DSM-5 criteria for gender dysphoria in child; family experiences of child’s gender identity; gender expression and social transition; and body image and body distress.	P	×	×	×
Child Semi-Structured Interview	Verbal identification with experienced gender; gender expression and social transition; age first realised and expressed gender identity; and body image and distress.	C	×	×	×
Young Person Questionnaire	DSM-5 criteria for gender dysphoria; distress around gender identity; gender expression and social transition; body image and body distress; and sexual orientation.	YP	×	×	×
Gender Similarity Task28	Perceived similarity to own-gender and other-gender peers.	C	×	×	×
Gender Diversity Questionnaire7	Verbal identification with expressed gender; gender fluidity; gender expression; age first realised and expressed gender identity.	YP	×	×	×
Utrecht Gender Dysphoria Scale29	Severity of gender dysphoria.	YP	×	×	×
Gender Identity Self Stigma Scale30	Internalised transphobia and stigma.	YP	×	×	×
CYP functioning
Child Behaviour Checklist31	Emotional reactivity; anxious/depressed; somatic complaints; withdrawn; sleep problems; attention problems; and aggressive behaviour.	P	×	×	×
Autism Quotient32	Autistic traits in child or adolescent.	P	×	×	×
Strengths and Difficulties Questionnaire33	Emotional symptoms; conduct problems; hyperactivity/inattention; peer relationship problems; and prosocial behaviour.	P and YP	×	×	×
Youth Self Report31	Anxious-depressed; withdrawn/depressed; somatic complaints; social problems; thought problems; attention problems; rule-breaking behaviour; and aggressive behaviour.	YP	×	×	×
Moods and Feelings Questionnaire34	Depressive symptoms in child or adolescent.	YP	×	×	×
Warwick-Edinburgh Mental Well-being Scale35	Mental well-being.	YP	×	×	×
Child and Youth Resilience Measure36	Brief screener for resilience processes in the lives of children and adolescents.	C and YP	×	×	×
Healthcare resource use
Child & Adolescent Service Use Schedule37	All-cause uses of hospital, community-based and private health and social care services.	P	×	×	×
Quality of life
Kidscreen-5238	Physical well-being, psychological well-being, moods and emotions, self-perception, autonomy, parent relations and home life, social support and peers, school environment, social acceptance (bullying), and financial resources.	P or C, YP	×	×	×
Child Health Utility 9 Dimensions39	Paediatric health-related quality of life for use in economic evaluation (quality adjusted life years).	P or C, YP	×	×	×
Physical measures
Parental height	Height in centimetres.	P	×
CYP pubertal development	Tanner stage.	P and YP	×	×	×
CYP height, weight, BMI	Height in centimetres; weight in kilograms.	P and YP	×	×	×

Child (C) ages for data collection are 3–11 years. Young people (YP) ages for data collection are ≥12 years. Parental (P) proxy measures are available for children (aged <8 years) not able to self-complete quality of life instruments.
BMI, body mass index; CYP, children and young people.