Table 1.

Included studies (n = 52).

Conventional RCTs (n = 42)
Author	Paper type (primary or secondary papera)	Participant age	Aim
Allen 2013 [80]	Primary (Feasibility)	13–17yrs	Assessed feasibility of recruiting young women into an RCT of caseload midwifery.
Allmark 2006 [45]	Secondary Primary paper Azzopardi 2009 [90]	≥36wks	Compared intensive care plus total-body cooling for 72 h with intensive care without cooling among term infants with asphyxial encephalopathy.
Banks 2012 [46]	Primary (Pilot)	5–16yrs	Assessed feasibility of carrying out a fully powered RCT comparing; care of childhood obesity intervention (COCO) and a primary care clinic intervention (PCC).
Barratt 2013 [81]	Secondary Primary paper Wake 2009 [104]	5–10yrs	In-depth understanding of why families chose not to participate in a community-based study on childhood obesity.
Bauchner 1996 [67]	Primary	3mth-6yrs	Do parents prefer antibiotic administration for treatment of acute otitis media by a single intramuscular (IM) injection or standard oral therapy for 10 days.
Blickman 2013 [68]	Primary	1–12yrs	Assessed the impact of a Certified Child Life Specialist (CCLS) on parent satisfaction, staff satisfaction, child satisfaction, and parent and staff perceptions of child pain and distress in a pediatric imaging department.
Byrne-Davis 2010 [47]	Secondary Primary paper Vora 2013 [103]	2–11yrs	Examined how recruitment looked to an observer and how it felt to parents, (of children with low-risk acute lymphoblastic leukemia) to identify how doctors' communication could promote or inhibit optimal recruitment.
Caldwell 2003 [30]	Secondary (Multiple RCTs)	Not stated	Explored parents' attitudes to children's participation in trials, identifying factors that influenced decision making and perceived risks and benefits. RCTs included oncology and renal: interventions not defined.
Carvalho 2013 [82]	Secondary Primary paper Moreira 2013 [99]	<3yrs	The understanding and perceptions of mothers regarding the informed consent and randomisation processes linked to an RCT that compared behavior management techniques for pediatric dental sedation.
Chappuy 2014 [38]	Secondary	Children - age not stated	Parental and child understanding of RCT participation (Acute lymphoblastic leukemia FRALLE 2000A protocol) and evaluations of the readability of written documents provided.
Duncan 2004 [69]	Primary	11mths-12yrs	Effectiveness of osteopathic manipulation, acupuncture or wait list control as a 6-month therapeutic adjunct for children with spastic cerebral palsy.
Eiser 2005 [49]	Secondary Primary paper Mitchell 2005 [98]	4–16yrs	Mothers' (of children newly diagnosed with Acute Lymphoblastic Leukemia: ALL) views regarding consent to randomised controlled trials.
Forsander 1995 [60]	Primary	12–15yrs	Evaluation of family attitudes in relation to the two 3wk care systems for diabetes management: early discharge from ward to training apartment and treatment on a ward in pediatric clinic.
Glogowska 2001 [50]	Secondary Primary paper Glogowska 2000 [94]	3–4yrs	Reported attitudes of parents whose child took part in a speech and language therapy RCT comparing immediate treatment and watchful waiting.
Harth 1990 [83]	Secondary Primary paper Van Asperen 1992 [101]	6mths-3yrs	Double-blind, placebo-controlled trial of ketotifen, a new and unlicensed (for Australia) oral asthma drug.
Hissink Muller 2011 [40]	Secondary (poster presentation) Primary paper Hissink Muller 2017 [96]	Children - age not stated	Comparison of three treatment strategies, and feedback relating to treatment preferences among parents of patients with recent onset juvenile idiopathic arthritis.
Hissink Muller 2012 [41]	Secondary (poster presentation) Primary paper Hissink Muller 2017 [96]	12–18yrs	Comparison of three treatment strategies, and feedback relating to equipoise among parents and patients with recent onset juvenile idiopathic arthritis.
Johnson 2007 [42]	Secondary	10–18yrs (and adults)	Assessed participant and parent experiences in the parenteral insulin arm of the Diabetes Prevention Trial (DPT-Type 1).
Johnson 2009 [43]	Secondary	10–18yrs (and adults)	Assessed the experiences of participants and parents of children in the oral insulin study of the Diabetes Prevention Trial (DPT-Type 1).
Jollye 2009 [52]	Secondary (Multiple RCTs)	Neonates	Explored the thoughts and feelings of parents in their decision-making process, in either choosing or declining to participate in neonatal RCTs.
Levi 2000 [70]	Secondary (Multiple RCTs)	2–18yrs	Retrospective parent perceptions of communication of their child's cancer diagnosis and the informed consent process.
Miner 2007 [71]	Primary	6mth-17yrs	To determine if nebulized fentanyl is a feasible alternative to IV fentanyl for the treatment of acute pain in children presenting to the emergency department (ED) with painful conditions.
Payne 2004 [54]	Secondary	3–12yrs	Views and preferences for anesthetic related issues important to parents (and adults) who took part in a prospective RCT.
(PENTA) Paediatric European Network for Treatment of AIDS 1999 [86]	Secondary (double-blind)	Children - age not stated	Described parents' experience of their child being enrolled in a HIV infection RCT, including the degree to which it interfered with life, and their feelings about use of deferred (placebo) and immediate antiretroviral treatment.
Rovers 2000 [62]	Primary	16-24mths	The effectiveness of ventilation tubes on the language development in infants with persistent otitis media with effusion (OME) compared to watchful waiting (WW).
Sammons 2007 [55]	Secondary Primary paper Atkinson 2007 [89]	6mth-16yrs	Parental views on the informed consent process, information provided, reasons for taking part and willingness to participate in future research. Compared motives of British and European parents.
Sandler 2014 [56]z	Primary	12–18yrs	Effectiveness of 3 methods of orthodontic anchorage supplementation, reporting orthodontists' and patients' values.
Sartain 2002 [57]	Primary	6wks-12yrs	Assessed the clinical effectiveness of a pediatric hospital at home service compared to conventional hospital care.
Schuttelaar 2010 [64]	Primary	≤16yrs	Compared the level of care from nurse practitioners with care delivered by dermatologists.
Sederberg-olsen 1998 [65]	Secondary (double blind) Primary paper Balle 1998 [91]	1–10yrs	Evaluated the efficacy of amoxicillin-clavulanate and penicillin-V in the treatment of secretory otitis media (SOM).
Shilling 2011 [28]	Secondary (Multiple RCTs) MASCOT: funding extension application rejected & trial closed prematurely [97] MENDS [88] POPs [still recruiting] TIPIT [108]	MASCOT: 6–15yrs MENDS: 3–15yrs POP: 4–18yrs TIPIT: < 28wks	Identify strategies to improve recruitment and trial conduct, by comparing practitioners' and parents' accounts of the invitation to enter a child into clinical trials.
Snowdon 1997 [58]	Secondary Primary paper UK Collaborative ECMO Trial Group [95]	Neonates	Exploration of parental reactions to random allocation of treatment in a neonatal RCT comparing two methods of life support; conventional management (CM) and extracorporeal membrane oxygenation (ECMO). Recruitment was stopped early, because data showed a clear advantage with ECMO.
Spandorfer 2005 [74]	Primary Loss of clinical equipoise and declining accrual rates led to trial termination.	8wk-3yrs	Compare oral rehydration therapy (ORT) and intravenous fluid therapy (IVF) in the treatment of viral gastroenteritis.
Sureshkumar 2012 [85]	Secondary Primary paper Craig 2009 [92]	<18yrs	To identify modifiable and unmodifiable factors associated with parental consent to a trial investigating long-term, low-dose antibiotics in preventing recurrent urinary tract infection.
Tercyak 1998 [75]	Secondary Primary paper Diabetes Control Complications Trial Research Group [93]	11–18yrs	Identify reasons/characteristics of adolescents who refuse or consent to participate in an RCT of intensive therapy (IT) for insulin-dependent diabetes mellitus.
Willey 2005 [59]	Primary	4–16yrs	Efficacy of oral or rectal route administered analgesia for post-operative pain.
Williams 2013 [77]	Primary	2–17yrs	Compared cast versus splint for distal radial buckle fractures in children in terms of parental and patient satisfaction, convenience and preference.
WoodgateZ 2010 [39]	Secondary (Multiple RCTs)	6mth-15yrs	In-depth understanding of Canadian parents' participation in decisions about childhood cancer clinical trials.
Woolfall 2013 [29]	Secondary (Multiple RCTs) MASCOT [97] funding extension application rejected & trial closed prematurely. MENDS [88] POPs [still recruiting] TIPIT [108]	MASCOT: 6–15yrs MENDS: 3–15yrs POP: 4–18yrs TIPIT: < 28wks	Explored how a parent's understanding of a trial might be associated with the way that the trial was explained during the discussion with a practitioner.
Wright 2005 [87]	Primary Recruitment was expected to take 3yrs but took 6yrs.	4–10yrs	Investigated early application hip spica compared with external fixation in pediatric femoral fractures. Recruitment was expected to take 3yrs but took 6yrs.
Wynn 2010 [78]	Secondary Primary paper Wang 2011 [105]	<18mths	In response to slow recruitment study coordinators evaluated factors that affected enrollment and accrual.
Young 2006 [79]	Secondary	7–17yrs	Reported results of two studies of social phobia, assessing the extent to which parental reluctance toward medication resulted in pre-treatment attrition in; behavioural, fluoxetine and placebo groups.
RCTs with non-randomised preference arms (n = 10)
Cunningham 2011 [48]	Secondary Trial 1: preference arm added and trial terminated early due to inadequate sample size.	Adolescents (age not stated)	Reported two RCTs, both terminated early due to inadequate sample size. Trial 1: Multi-center Orthodontic RCT which compared two different methods of treating a specific type of malocclusion in adolescents. (Trial 2: RCT, no preference data).
Gowers 2010 [51]	Primary	12–18yrs	Compared the clinical effectiveness of inpatient against outpatient treatment and of generalist against specialist management.
Lock 2010 [53]	Primary Trial extended from 5 to 7yrs to increase patient recruitment.	4–15yrs	An embedded qualitative study informed the development of the RCT, it explored patient/parent(s) preferences for different treatment options in patients with recurrent sore throats who had recently been referred to ENT clinic. Extended from 5 to 7yrs to increase patient recruitment.
Mattila 2007 [61]	Primary	≤2yrs	Assessed adenoidectomy in connection with tympanostomy compared with tympanostomy only in preventing otitis media in children.
Paradise 1984 [72]	Primary	3–15yrs	Assessed the efficacy of tonsillectomy and adenoidectomy.
Paradise 1990 [73]	Primary	1–15yrs	Assessed the efficacy of adenoidectomy, comparing surgical and non-surgical management, with equivalent non-randomised preference arms.
Reddihough 1998 [84]	Primary	12-36mths	Compared conductive education (CE) program with equivalent intensity traditional neurodevelopmental programs of rehabilitation for young children with Cerebral Palsy.
Rovers 2001 [106]	Primary	9–12mths	Compared ventilation tubes (VT) and watchful waiting (WW) in the management of patients with otitis media with effusion. The generaliszability of randomised patients with eligible non-randomised patients was studied via preference arms.
Weinstein 2013 [76]	Primary Preference arms added after 3yrs of recruitment.	10–15yrs	The effectiveness of bracing, compared with observation in preventing progression of the curve to 50° or more in idiopathic scoliosis patients, with equivalent non-randomised preference arms.
Van Wijk 2014 [66]	Secondary Primary paper Van Wijk 2014 [102]	4.5–6.5mths	Primary: Effectiveness of helmet therapy for positional skull deformation compared with the natural course of the condition Secondary: Assess parents' decision for helmet therapy in infants with skull deformation.

^aPrimary papers were defined as those reporting primary RCT outcome(s). Secondary papers were those reporting embedded/related studies (e.g. qualitative) describing patient/parent experience of trial involvement, reasons for decline, consenting and recruitment.