Table 2.
Protocol characteristics (total protocols = 824)
| Year of publication | Number of protocols (n, %) |
| 2014 | 85 (10.3%) |
| 2015 | 108 (13.1%) |
| 2016 | 125 (15.2%) |
| 2017 | 126 (15.3%) |
| 2018 | 161 (19.5%) |
| 2019 | 219 (26.6%) |
| Level of randomisation | |
| Cluster RCTs | 132 (16%) |
| Individually randomised RCTs | 692 (84%) |
| Funding type | |
| Commercial triala | 98 (11.9%) |
| Non-commercial trial | 666 (80.8%) |
| No funding | 27 (3.3%) |
| Unclear—no information provided | 33 (4%) |
| Type of intervention | |
| Non-drug trial | 593 (72%) |
| Drug trial | 138 (16.7%) |
| Mix of intervention types | 23 (2.8%) |
| Surgical trial | 55 (6.7%) |
| Medical device trial | 15 (1.8%) |
| Patient populationb | Number of protocols |
| Vulnerable populations | 250 (30.3%) |
| Mix of vulnerable and non-vulnerable populations | 181 (22%) |
| Not vulnerable | 73 (8.9%) |
| Unclear | 320 (38.8%) |
|
Planned sample sizec Individual level randomisation (n = 692) |
Number of protocols |
| 100 participants or less | 222 (32.1%) |
| 101–200 participants | 175 (25.3%) |
| 201–300 participants | 84 (12.1%) |
| 301–400 participants | 58 (8.4%) |
| 401–500 participants | 19 (2.7%) |
| 501 participants and greater | 121 (17.5%) |
| Overlap of categories | 2 (0.3%) |
| Unclear from protocol | 11 (1.6%) |
|
Planned sample sized Cluster trials (n = 132) |
Number of protocols |
| 100 clusters or less | 110 (83.3%) |
| 101–200 clusters | 8 (6.1%) |
| 201–300 clusters | 4 (3%) |
| 301–400 clusters | |
| 401–500 clusters | |
| 501 clusters and greater | 1 (0.8%) |
| Unclear from protocol |
9 protocols (6.8%) – cluster size unclear but provided the participant size in 7 protocols • 1202 participants • 382 participants • 426 participants • 342 participants • 90 participants • 300 participants • 600 participants |
| Clinical Specialtye | Number of protocols |
| Public Health | 131 (15.9%) |
| Musculoskeletal | 80 (9.7%) |
| Oncology | 77 (9.3%) |
| Mental Health | 74 (9%) |
| Cardiology | 74 (9%) |
| Obstetrics and Gynaecology | 65 (7.9%) |
| Neurology | 62 (7.5%) |
| Diabetes and Endocrinology | 35 (4.2%) |
| Respiratory | 33 (4%) |
| Sexual Health and STIs | 30 (3.6%) |
| Nephrology | 19 (2.3%) |
| Vascular diseases | 19 (2.3%) |
| Gastroenterology | 17 (2.1%) |
| Paediatrics | 12 (1.5%) |
| Surgery and Anaesthesia | 11 (1.3%) |
| Dental health | 10 (1.2%) |
| Haematology | 8 (1%) |
| Infectious Disease | 8 (1%) |
| Intensive care | 7 (0.8%) |
| Ophthalmology | 7 (0.8%) |
| Hepatology | 6 (0.7%) |
| Otology | 6 (0.7%) |
| Autoimmune diseases | 6 (0.7%) |
| Emergency care | 4 (0.5%) |
| Palliative care | 3 (0.4%) |
| Otolaryngology | 3 (0.4%) |
| Dermatology | 3 (0.4%) |
| Genetics | 3 (0.4%) |
| Intellectual Disabilities | 2 (0.2%) |
| Pathology | 1 (0.1%) |
| Rehabilitation | 1 (0.1%) |
| Trial Methods | 1 (0.1%) |
| Secondary care | 1 (0.1%) |
| Primary care | 1 (0.1%) |
| Pharmacy care | 1 (0.1%) |
| Geriatric medicine | 1 (0.1%) |
| Orthopaedics | 1 (0.1%) |
| Appendicitis | 1 (0.1%) |
| Patient reported primary outcome | Number of protocols |
| Yes | 298 (36.2%) |
| Partlyf | 78 (9.5%) |
| No | 440 (53.4%) |
| Unclear from protocol | 8 (1%) |
| Number of follow-up assessments | Number of protocols |
| 1 follow-up assessment | 124 (15%) |
| 2 follow-up assessments | 238 (28.9%) |
| 3 follow-up assessments | 156 (18.9%) |
| 4 follow-up assessments | 105 (12.7%) |
| 5 follow-up assessments | 34 (4.1%) |
| 6 or more follow-up assessments | 106 (12.9%) |
| Unclear from protocol | 61 (7.4%) |
| Follow-up method for data collection | Number of protocols |
| In person clinic visit | 290 (35.2%) |
| Postal questionnaire | 13 (1.6%) |
| Electronic questionnaire /online assessment | 49 (5.9%) |
| Telephone call | 24 (2.9%) |
| Via patient records or databasesg | 25 (3%) |
| Home visits/visits to site outside the clinic by researcher | 37 (4.5%) |
| A combination of follow-up methods | 326 (39.6%) |
| All data collected whilst the participant is in the hospital | 36 (4.4%) |
| Unclear from protocol | 24 (2.9%) |
| Routine data sources for data collectionh | |
| Yes | 164 (19.9%) |
| No | 660 (80.1%) |
| Trial type | |
| Pilot or feasibility trial | 102 (12.4%) |
| RCTs | 722 (87.6%) |
| RCT protocols reported using SPIRIT guidelines | |
| Yes | 253 (35%) |
| No | 469 (65%) |
| Pilot and feasibility protocols reported using SPIRIT guidelines | |
| Yes | 35 (34.3%) |
| No | 67 (65.7%) |
aCommerial trials were defined as a trial that has any type of funding or donation from a private for-profit company/organisation for example partly funded by pharma or product provided by a commercial company was classified as a commercial trial
bVulnerable populations were defined by this reviews’ authors via local ethics committee definition [32] and ICH GCP definition [20] these included; infants and children aged 17 years and under, pregnant women, institutionalised individuals (prisoners, in nursing homes, mental health institutions), critically ill/ICU patients/patients on ventilators unable to provide consent so deferred consent is gained, where stated in the protocol deferred consent is obtained, adults aged 60 and over, participants with learning disabilities, suffers of dementia, adults with terminal illness, homeless individuals and refugees, adults with mental illness, and members of the armed forces and medical/nursing/dental/pharmacy students where there is a hierarchy in the trial that would influence the decision to take part voluntarily
cThe sample size groupings contain protocols that stated they would recruit “at least” or a “minimum (number) of” participants for example if a protocol stated they would recruit at least 80 participants this has been grouped into category 1. “100 participants or less”. For dyad pairs, these have been grouped in terms of total number of participants for example 100 participants and their dyad, i.e. 200 participants would be grouped in category 2. “101–200 participants”
dThe sample size groupings contain protocols that stated they would recruit “at least” or a “minimum (number) of” clusters for example if a protocol stated they would recruit at least 80 clusters this has been grouped into category 1. “100 clusters or less”
eCategories were based on clinical specialty for example surgery for cancer was classed under “Oncology” rather than “Surgery and Anaesthesia”, only surgeries or anaesthetic procedures for non-specific clinical area/none of the clinical specialty categories listed above were grouped under “Surgery and Anaesthesia” for example “elective non-cardiac surgery”. Similarly, “Paediatrics” only contains paediatric trials that did not involve a clinical specialty area listed above, for example “Chronic Fatigue Syndrome” was include in “Paediatrics” whereas “Children younger than 5 years of age with acute gastroenteritis” was grouped into “Gastroenterology”
fPartly patient reported means aspects of the primary outcome were reported by the patient and other aspects were not
gIn this category, participants are not directly followed up, all follow-up is via a database/registry/routine data source
hIn this category, routine data sources were used for outcome data/follow-up data/demographic data on participants, these routine sources include patient records, registries, hospital databases and medical records