Question | Category | Response statistics | ||||
---|---|---|---|---|---|---|
n | N | n/N% | ||||
6 | a | Assuming that you have stratified by centre, do you combine by the stratification factor for the purpose of analysis? If so how? See Table5for further details. | Yes | 24 | 44 | 55% |
Pre-specified grouping rules at design stage | 19 | 24 | 80% | |||
Ad hoc approach, e.g. determined after design due to small numbers per group | 14 | 24 | 58% | |||
Other grouping rule or further details provided | 6 | 24 | 26% | |||
No | 17 | 44 | 39% | |||
No response | 3 | 44 | 7% | |||
b | Assuming that you have stratified by treatment provider, do you combine by the stratification factor for the purpose of analysis? If so how? | Yes | 16 | 44 | 36% | |
Pre-specified grouping rules at design stage | 12 | 16 | 75% | |||
Ad hoc approach, e.g. determined after design due to small numbers per group | 7 | 16 | 44% | |||
See Table5for further details. | Other grouping rule or further details provided | 5 | 16 | 31% | ||
No | 14 | 44 | 32% | |||
No experience with trials of this type | 1 | 44 | 2% | |||
No response | 13 | 44 | 30% | |||
7 | Does your Unit include centre in the statistical model when comparing treatment? | Yes | 39 | 44 | 89% | |
But only if it was used to stratify randomisation | 18 | 39 | 46% | |||
Always | 6 | 39 | 15% | |||
Sometimesa | 15 | 39 | 38% | |||
No, never | 3 | 44 | 7% | |||
No responseb | 2 | 44 | 5% | |||
a | If yes, and assuming that the sample size allows either, would you treat this effect as fixed or random? See Supplementary Box3for further details. | Fixed or random, depending on circumstances | 14 | 39 | 36% | |
Fixed | 11 | 39 | 28% | |||
Random | 12 | 39 | 31% | |||
No response | 2 | 39 | 5% | |||
8 | Does your Unit include treatment provider in the statistical model when comparing treatment? | Yes | 26 | 44 | 59% | |
But only if it was used to stratify randomisation | 8 | 26 | 31% | |||
See Supplementary Box4for further details. | Always | 0 | 26 | 0% | ||
Sometimesc | 18 | 26 | 69% | |||
No, never | 13 | 46 | 30% | |||
No responsed | 5 | 44 | 11% | |||
a | If yes, and assuming that the sample size allows either, would you treat this effect as fixed or random? | Fixed or random, depending on circumstances | 4 | 26 | 15% | |
Fixed | 2 | 26 | 8% | |||
Random | 18 | 26 | 69% | |||
No response | 2 | 26 | 8% | |||
b | If yes, has this effect ever been treated as time-varying within the statistical model? | Yes | 2 | 26 | 8% | |
No | 21 | 26 | 81% | |||
No response | 3 | 26 | 12% | |||
9 | In each of the following scenarios, regardless of the randomisation stratification approach, has a treatment by centre or surgeon interaction investigated, in trials that your Unit has run? Select all that apply. See Supplementary Table6for further details. | |||||
A | Large sample size,e recruiting in several centres, each with multiple treatment providers | Experience in trial type | 35 | 44 | 80% | |
Centre | 16 | 35 | 46% | |||
Treatment provider | 4 | 35 | 11% | |||
Both | 3 | 35 | 9% | |||
Neither | 20 | 35 | 57% | |||
No experience in trial type | 7 | 44 | 16% | |||
No response | 2 | 44 | 5% | |||
B | Small sample size,f With centres each recruiting 2 to 3 patients | Experience in trial type | 30 | 44 | 68% | |
Centre | 5 | 30 | 17% | |||
Treatment provider | 0 | 30 | 0% | |||
Both | 0 | 30 | 0% | |||
Neither | 25 | 30 | 83% | |||
No experience in trial type | 12 | 44 | 27% | |||
No response | 2 | 44 | 5% | |||
C | Recruiting in several centres, where treatment providers treat patients across recruiting centres (treatment provider is not unique to a centre) | Experience in trial type | 15 | 44 | 34% | |
Centre | 4 | 15 | 27% | |||
Treatment provider | 1 | 15 | 7% | |||
Both | 0 | 15 | 0% | |||
Neither | 11 | 15 | 73% | |||
No experience in trial type | 27 | 44 | 61% | |||
No response | 2 | 44 | 5% | |||
D | A trial investigating a surgical intervention, recruiting from several centres, each with multiple treatment providers | Experience in trial type | 21 | 44 | 48% | |
Centre | 5 | 19 | 24% | |||
Treatment provider | 3 | 19 | 14% | |||
Both | 1 | 19 | 5% | |||
Neither | 14 | 19 | 67% | |||
No experience in trial type | 19 | 44 | 43% | |||
No response | 4 | 44 | 9% | |||
E | Recruiting from several centres, each with multiple treatment providers, comparing substantially different interventions, e.g. surgery to an injection | Experience in trial type | 14 | 44 | 32% | |
Centre | 5 | 14 | 36% | |||
Treatment provider | 1 | 14 | 7% | |||
Both | 0 | 14 | 0% | |||
Neither | 9 | 14 | 64% | |||
No experience in trial type | 26 | 44 | 59% | |||
No response | 4 | 44 | 9% | |||
In scenarios where Unit has experience, approaches to stratification changes across scenario, i.e. within-Unit variation to stratification | Different approaches across scenarios | 12 | 44 | 27% | ||
Same approach across all scenarios | 24 | 44 | 55% | |||
No response to Question 9 | 8 | 44 | 18% | |||
10 | a | If a positive treatment effect is found, does your Unit explore heterogeneity of treatment effects by centre? See Supplementary Table7for further details. | Yes | 32 | 44 | 73% |
No | 9 | 44 | 20% | |||
No response | 3 | 44 | 7% | |||
i. If yes to a, do you explore by graphical display? | Yes | 31 | 32 | 97% | ||
No | 0 | 32 | 3% | |||
No response | 1 | 32 | 3% | |||
ii. If yes to a, do you explore by analytical methods, e.g. significance testing? | Yes | 22 | 32 | 69% | ||
No | 5 | 32 | 16% | |||
No response | 5 | 32 | 16% | |||
b | If a positive treatment effect is found, does your Unit explore heterogeneity of treatment effects by treatment provider? See Supplementary Table8for further details. | Yes | 12 | 44 | 27% | |
No | 23 | 44 | 52% | |||
No response | 9 | 44 | 20% | |||
i. If yes to b, do you explore by graphical display? | Yes | 11 | 12 | 92% | ||
No | 0 | 12 | 0% | |||
No response | 1 | 12 | 8% | |||
ii. If yes to b, would you explore by analytical methods, e.g. significance testing? | Yes | 9 | 12 | 75% | ||
No | 1 | 12 | 8% | |||
No response | 2 | 12 | 17% |