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Table 2 Methods for managing clustering and learning by design

From: Managing clustering effects and learning effects in the design and analysis of multicentre randomised trials: a survey to establish current practice

Question

Category

Response statistics

n

N

n/N%

2

Does your Unit have any multicentre trials that do not stratify randomisation by centre?

Yes

25

44

57%

No

18

44

41%

See Table4for further details.

No response

1

44

2%

3

In each of the following scenarios, how was the randomisation stratified in trials that your Unit has run? Select all that apply.

See Supplementary Table 5for further details.

   

A

Large sample size,a recruiting in several centres, each with multiple treatment providers

Experience in trial type

39

44

89%

 Centre

34

39

87%

 Treatment provider

3

39

8%

 Both

10

39

26%

 Neither

1

39

3%

No experience in trial type

4

44

9%

No response

1

44

2%

B

Small sample size,b recruiting in several centres, each with multiple treatment providers

Experience in trial type

31

44

70%

 Centre

24

31

77%

 Treatment provider

2

31

6%

 Both

2

31

6%

 Neither

7

31

23%

No experience in trial type

12

44

27%

No response

1

44

2%

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

16

44

36%

 Centre

14

16

88%

 Treatment provider

3

16

19%

 Both

1

16

6%

 Neither

0

16

0%

No experience in trial type

27

44

61%

No response

1

44

2%

D

A trial investigating a surgical intervention, recruiting from several centres, each with multiple treatment providers

Experience in trial type

25

44

57%

 Centre

21

25

84%

 Treatment provider

3

25

12%

 Both

5

25

20%

 Neither

3

25

12%

No experience in trial type

17

44

39%

No response

2

44

5%

E

Recruiting from several centres, each with multiple treatment providers, comparing substantially different interventions e.g. surgery to an injection

Experience in trial type

16

44

36%

 Centre

13

16

81%

 Treatment provider

0

16

0%

 Both

2

16

13%

 Neither

2

16

13%

No experience in trial type

26

44

59%

No response

2

44

5%

In scenarios where Unit has experience, approaches to stratification changes across scenario, i.e. within-Unit variation to stratification

Different approaches across scenarios

20

44

46%

Same approach across all scenarios

19

44

43%

No response to Question 3

5

44

11%

4

In the trials run by your Unit, have you defined a minimum level of expertise for the health professionals participating in the trial in terms of:

Treating the condition within the patient population

24

44

55%

Delivering the trial intervention

31

44

70%

Setting a minimum professional level of treatment providers

22

44

50%

Other approach:

   

 Based on paramedic experience (defined by years in service)

1

44

2%

 Based on surgeon experience (at or beyond a certain level)

1

44

2%

 Centre required to conduct a certain number of operations per year

1

44

2%

 Clinical decision for Chief Investigator

1

44

2%

 Deliverer required to pass surgical and radiotherapy quality assurance

1

44

2%

 Depends on phase of trial—early or pragmatic require different levels

1

44

2%

 In our stepwise study, all therapists were experienced but the intervention was brand new

1

44

2%

 Investigators who define research question are experts in the field and have trained staff to deliver intervention

1

44

2%

 No consistent approach across all our studies.

1

44

2%

 No Unit-wide policy—decided trial by trial depending on intervention and setting

1

44

2%

 Surgeon manuals signed off by ‘senior’ surgeon prior to participation

1

44

2%

 Surgical team led by consultant, who submits video measured for quality assurance, prior to participation

1

44

2%

 These have been implicitly taken as a Chief Investigator and Principal Investigator

1

44

2%

 Training provided to health care professionals in order to participate

1

44

2%

 No, or no response

5

44

11%

5

Has your Unit conducted trials with an expertise-based design, in which participating treatment providers provide only the intervention in which they have expertise?

Yes, when applicablec

13

44

30%

No, with justification

1

44

2%

No

26

44

59%

No response

4

44

9%

  1. aWith centres each recruiting at least 10 patients
  2. bWith centres each recruiting 2 to 3 patients
  3. cWe only have one grant application for which we’ve proposed an expertise-based design this year but no prior experience of running a trial with such a design before [ID22]
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Trials

ISSN: 1745-6215