Subgroup analyses
Publications in high impact journals (impact factor ≧4) after 2010 vs
low impact journals after 2010 showed potential higher rates of context
placement (52/67 [78%] vs 49/71 [69%]; RR 1.1, 95%CI
0.9-1.4), information gain (47/67 [70%] vs 32/71 [45%]; RR
1.56, 95%CI 1.15-2.10) and transparency features: trial registration
(62/67 [93%] vs 33/71 [47%]; RR 1.99, 95%CI 1.54-2.58),
published protocols (17/67 [25%] vs 4/71 [6%]; RR 4.50, 95%CI
1.60-12.7), and data availability (9/67 [13%] vs 2/71 [3%]; RR
4.77, 95%CI 1.07-21.27). However, only 36 of these 67 high impact
journal publications (54%, 95%CI 42-65%) reported a complete power
calculation and 17/67 (25%, 95%CI 16-37%) used a surrogate and/or
composite outcomes as their primary outcome (Table S4). Some examples of
surrogate outcomes: “cervical dilation” in women receiving home
uterine monitoring for early PTB detection; “number of hospital
antenatal visits” in women receiving routine doppler ultrasound;
biochemical test results like HbA1c values in diabetic pregnant women or
CRP values in pregnant women treated for a (vaginal) infection (Table
S6).
Out of the 350 trials, 259 (74%) reported a primary outcome of which
97/259 (38%) reported a statistically significant result
(P<0.05) in the primary outcome(s). Trials with a
non-significant finding in the primary outcome(s) most frequently
satisfied several usefulness criteria. This is most prominently for
information gain (RR 1.27, 95%CI 1.03-1.56) and transparency features
like trial registration (RR 1.31, 95%CI 0.97-1.78), preregistration (RR
1.34, 95%CI 0.73-2.4) and protocol availability (RR 2.0, 95%CI
0.76-5.34) (Table S4).