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Table 5 Class allocation – likelihood of being in Class 2 over Class 1

From: How do study design features and participant characteristics influence willingness to participate in clinical trials? Results from a choice experiment

Characteristics

Reference level

Levels

MLE (SE)

Constant

-

-

-0.283 (0.432)

Disease-related variables

 Time since first diagnosis, years

0–5

 ≥ 6

-0.156 (0.140)

 Number of medical conditions

1–2

 ≥ 3

-0.042 (0.247)

 Anemia

No

Yes

-0.032 (0.184)

 Anxiety

No

Yes

0.138 (0.191)

 Depression

No

Yes

-0.169 (0.200)

 Diabetes (Type I or Type II)

No

Yes

0.222 (0.167)

 Heart disease

No

Yes

0.037 (0.166)

 Migraine

No

Yes

0.215 (0.171)

 Multiple sclerosis

No

Yes

0.191 (0.222)

 Rheumatoid arthritis

No

Yes

0.013 (0.159)

 Cancer

No

Lower mortality

-0.087 (0.206)

 

No

Higher mortality

0.126 (0.199)

Treatment-related variables

 Number of previous lines of treatment

0–2

 ≥ 3

-0.304 (0.146)**

 Affordability of current medication

I can easily afford my medications

I can afford my medications

-0.200 (0.142)

 

I can easily afford my medications

I struggle to pay for my medications

-0.403 (0.245)*

 Experience of treatment side effects

None

Mild

0.097 (0.149)

 

None

Severe

0.024 (0.210)

 COVID vaccine

No

Yes

-0.062 (0.152)

 Direct experience of clinical trial

No

Yes

0.245 (0.188)

Health-related variables

 I feel fatigued

Not at all/A little Bit

Somewhat/Quite a Bit/Very Much

-0.288 (0.165)*

 I have had difficulty with mobility

Not at all/A little Bit

Somewhat/Quite a Bit/Very Much

-0.021 (0.178)

 I have had pain or discomfort

Not at all/A little Bit

Somewhat/Quite a Bit/Very Much

0.053 (0.165)

 I have been anxious or depressed

Not at all/A little Bit

Somewhat/Quite a Bit/Very Much

0.126 (0.170)

 I have to limit my social activity because of my health

Not at all/A little Bit/Somewhat

Quite a Bit/Very Much

0.372 (0.184)**

 I have had difficulty with performing my usual activities

Not at all/A little Bit/Somewhat

Quite a Bit/Very Much

0.042 (0.215)

 Current QoL (Classification)

0–7

 ≥ 8

0.276 (0.222)

 QoL vs. last year

Improve

Same/Deteriorate

0.098 (0.149)

 Self-perceived likelihood to live to average age a

Neutral/High

Low

0.096 (0.184)

 Self-perceived future quality of life

Improve

Same/Deteriorate

-0.130 (0.185)

Sociodemographic variables

 Age, years

18–50

51–65

0.279 (0.209)

 

18–50

 ≥ 66

0.946 (0.299)***

 Sex at birth

Male

Female

0.068 (0.130)

 Country of residence

USA

Poland

0.218 (0.245)

  

China

0.195 (0.242)

 Paid job

Yes

No

-0.213 (0.190)

 Education

Other than university

University

-0.168 (0.163)

 Living alone

Yes

No

0.279 (0.191)

 Looking after dependent

Yes

No

0.094 (0.154)

Attitudinal variables

 Trust in medical researchers b

Low (1–3)

High (4–5)

-0.035 (0.186)

 Altruism c

Low (1–3)

High (4–5)

-0.020 (0.179)

Other variables

 Survey version

Version 1

Version 2

0.154 (0.124)

  1. Abbreviations: MLE maximum likelihood estimation, QoL quality of life, SE standard error
  2. *p < 0.1; **p < 0.05; ***p < 0.01
  3. a Participants asked the likelihood they will live for the next 50 years if aged 18–35, the next 40 years if aged 36–50, the next 25 years if aged 51–65, or the next 10 years if aged ≥ 66
  4. b Trust in medical researchers assessed by asking participants to rate their agreement with item q3 of the Research Attitude Questionnaire [30]: ‘Medical researchers can be trusted to protect the interests of people who take part in their studies’. Rated on a scale of 1 (strongly disagree) to 5 (strongly agree)
  5. c Altruism assessed by asking participants to rate their agreement with item q4 of the Research Attitude Questionnaire [30]: ‘We all have some responsibility to help others by volunteering for medical research’. Rated on a scale of 1 (strongly disagree) to 5 (strongly agree)