Table 1

Characteristics of the studied external randomised pilot trial publications

Completed (n=37)
n (%)
Protocol (n=123)
n (%)
Total (n=160)
n (%)
Journal
British Medical Journal (BMJ) Open11 (30)34 (28)45 (28)
Pilot and Feasibility Studies (PAFS)21 (57)56 (46)77 (48)
Trials2 (5)33 (27)35 (22)
Public Library of Science (PLoS) One3 (8)0 (0)3 (2)
Country
 Australia6 (16)4 (3)10 (6)
 Brazil0 (0)1 (1)1 (1)
 Canada4 (11)15 (12)19 (12)
 China0 (0)4 (3)4 (3)
 Denmark0 (0)1 (1)1 (1)
 Germany1 (3)1 (1)2 (1)
 Korea0 (0)1 (1)1 (1)
 Nepal1 (3)2 (2)3 (2)
 New Zealand2 (5)1 (1)3 (2)
 Norway1 (3)0 (0)1 (1)
 Ireland0 (0)5 (4)5 (3)
 Sweden1 (3)1 (1)2 (1)
 Tanzania0 (0)1 (1)1 (1)
 Thailand0 (0)1 (1)1 (1)
 The Netherlands0 (0)2 (2)2 (1)
 UK19 (51)68 (55)87 (54)
 USA2 (5)14 (11)16 (10)
 Zimbabwe0 (0)1 (1)1 (1)
Funder
 Industry2 (5)2 (2)4 (3)
 Non-industry32 (86)115 (94)147 (92)
 A combination1 (3)4 (3)5 (3)
 Unknown2 (5)1 (1)3 (2)
 Trial did not receive funding0 (0)1 (1)1 (1)
Therapeutic areas
 Complementary medicine0 (0)1 (1)1 (1)
 Anaesthesia1 (3)1 (1)2 (1)
 Cardiology0 (0)3 (2)3 (2)
 Critical care1 (3)7 (6)8 (5)
 Endocrinology0 (0)6 (5)6 (4)
 Gastroenterology1 (3)3 (2)4 (3)
 Geriatrics1 (3)4 (3)5 (3)
 Hepatology0 (0)1 (1)1 (1)
 Infectious diseases0 (0)3 (2)3 (2)
 Musculoskeletal6 (16)4 (3)10 (6)
 Nephrology0 (0)1 (1)1 (1)
 Neurology3 (8)12 (10)15 (9)
 Obstetrics/gynaecology2 (5)6 (5)8 (5)
 Oncology4 (11)7 (6)11 (7)
 Ophthalmology0 (0)1 (1)1 (1)
 Orthopaedics2 (5)1 (1)3 (2)
 Other2 (5)3 (2)5 (3)
 Otolaryngology (ENT)2 (5)1 (1)3 (2)
 Paediatrics2 (5)3 (2)5 (3)
 Pain1 (3)0 (0)1 (1)
 Palliative care0 (0)3 (2)3 (2)
 Psychiatry/psychology2 (5)19 (15)21 (13)
 Public health2 (5)15 (12)17 (11)
 Respiratory0 (0)2 (2)2 (1)
 Rheumatology0 (0)1 (1)1 (1)
 Surgery3 (8)8 (7)11 (7)
 Trauma2 (5)7 (6)9 (6)
Intervention type
 Drug4 (11)9 (7)13 (8)
 Surgery/procedure6 (16)13 (11)19 (12)
 Counselling/lifestyle/physiotherapy22 (59)72 (59)94 (59)
 Equipment4 (11)5 (4)9 (6)
 Other1 (3)24 (20)25 (16)
Sample size target*
 Mean (SD)72.8 (62.5)258.5 (1215.7)217.3 (1074.9)
 Median (IQR)60 (32–90)60 (40–100)60 (40–100)
 Min-Max6–30020–12 0006–12 000
Cluster randomised pilot trials(n=3)(n=18)(n=21)
Number of clusters
 Mean (SD)7.3 (2.3)9.7 (11.6)9.3 (10.7)
 Median (IQR)6 (6–10)6 (3–10)6 (4–10)
 Min-Max6–102–452–45
Number of arms
 232 (86)111 (90)143 (89)
 >25 (14)12 (10)17 (11)
Number of centres
 Single centre19 (51)36 (29)55 (34)
 Multicentre18 (49)84 (68)102 (64)
 Unclear0 (0)3 (2)3 (2)
Feasibility objective/s explicitly described as primary
 Yes9 (24)62 (50)71 (44)
 No28 (76)61 (50)89 (56)
Trial outcomes address trial objectives
 Yes18 (49)91 (74)109 (68)
 No0 (0)1 (1)1 (1)
 Somewhat†19 (51)31 (25)50 (31)
Completely defined prespecified assessments or measurements stated
 Yes27 (73)113 (92)140 (88)
 Not for every outcome10 (27)10 (8)20 (13)
Hypothesis testing
 Yes2 (5)16 (13)18 (11)
 Yes, exploratory/caution advised18 (49)43 (35)61 (38)
 No17 (46)64 (52)81 (51)
Number of uncertainties reported
 One0 (0)1 (1)1 (1)
 Multiple37 (100)122 (99)159 (99)
Where uncertainties are first reported (excluding abstract)
 Introduction0 (0)1 (1)1 (1)
 Research question(s)2 (5)4 (3)6 (4)
 Aim(s)5 (14)16 (13)21 (13)
 Objective(s)10 (27)62 (50)72 (45)
 Outcome(s)9 (24)17 (14)26 (16)
 Outcome measure(s)7 (19)16 (13)23 (14)
 Analysis0 (0)2 (2)2 (1)
 Within the text under a feasibility/uncertainty heading2 (5)1 (1)3 (2)
 Throughout the text, not in one specific area2 (5)4 (3)6 (4)
  • Percentages may not sum up to 100 due to rounding.

  • *Where publications reported a sample size target range (eg, 12–16 participants), the lower bound of the target is included. A sample size target was not reported in two publications (both reporting completed pilot trials and including the actual number of recruited participants).

  • †Trial objective was vague (eg, to ‘assess feasibility’) and the specific areas of feasibility were not explicitly stated.

  • ENT, ear, nose and throat.