Table 3

Reported items of research methodology over the study period

Methodology itemYearP value
1997
n=299*
2002
n=319*
2007
n=396*
2012
n=635*
2017
n=654*
Multicentre study
n, % (95% CI)
64
21.6 (17.2 to 26.8)
76
24.6 (20.0 to 29.9)
101
26.4 (22.1 to 31.2)
186
31.7 (28.0 to 35.7)
223
38.9 (34.9 to 43.0)
<0.001
International collaboration
n, % (95% CI)
3
1.0 (0.3 to 3.2)
8
2.6 (1.2 to 5.2)
13
3.4 (1.9 to 5.9)
40
6.8 (5.0 to 9.2)
58
10.1 (7.8 to 12.9)
<0.001
Experimental design†
 n, % (95% CI)
78
26.4 (21.5 to 31.8)
63
20.3 (16.0 to 25.3)
74
19.4 (15.6 to 23.8)
130
22.2 (18.9 to 25.8)
115
20.0 (16.8 to 23.5)
0.17
Convenience sampling
n, % (95% CI)
79
26.9 (22.0 to 32.4)
92
29.6 (24.6 to 35.1)
109
28.5 (24.1 to 33.4)
137
23.6 (20.2 to 27.3)
116
20.2 (17.0 to 23.7)
0.006
Consecutive sampling
n, % (95% CI)
124
42.0 (36.4 to 47.9)
145
46.6 (41.0 to 52.3)
192
50.3 (45.1 to 55.4)
316
54.0 (49.9 to 58.1)
344
59.9 (55.8 to 64.0)
<0.001
Blinding
n, % (95% CI)
66
22.4 (17.8 to 27.7)
70
22.5 (18.1 to 27.6)
76
20.0 (16.1 to 24.4)
95
16.2 (13.4 to 19.5)
58
10.1 (7.8 to 12.9)
<0.001
Sample size calculated
n, % (95% CI)
54
18.3 (14.2 to 23.3)
46
14.8 (11.1 to 19.3)
78
20.4 (16.6 to 24.9)
151
25.7 (22.3 to 29.5)
129
22.5 (19.2 to 26.2)
0.002
Inferential statistics
n, % (95% CI)
97
32.8 (27.5 to 38.5)
130
41.8 (36.3 to 47.5)
178
46.7 (41.6 to 51.9)
318
54.2 (50.0 to 58.3)
339
58.9 (54.7 to 62.9)
<0.001
CIs
n, % (95% CI)
117
39.5 (34.0 to 45.4)
169
54.3 (8.6 to 60.0)
251
66.1 (61.0 to 70.8)
429
73.1 (69.3 to 76.6)
407
70.7 (66.7 to 74.3)
<0.001
P values
n, % (95% CI)
182
61.7 (55.9 to 67.2)
210
67.7 (62.2 to 72.9)
238
62.5 (57.4 to 67.3)
442
75.3 (71.6 to 78.7)
449
78.0 (74.3 to 81.2)
<0.001
  • *Some denominators vary due to missing data.

  • †Randomised controlled (parallel or crossover), pre/postinterventional, quasiexperimental, cluster randomised, other experimental.