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Table 4 Final list of variable attributes and levels in the DCE

From: A novel design process for selection of attributes for inclusion in discrete choice experiments: case study exploring variation in clinical decision-making about thrombolysis in the treatment of acute ischaemic stroke

Attribute Levels Rationale
1. Systolic blood pressure a. 140 mm/Hga b. 185 mm/Hg c. 200 mm/Hg • Highest ranked attribute in Stage 3 phases 1 and 2 • Levels include those across rage from ‘safe to offer thrombolysis’ to ‘grey are’ to ‘outside the thrombolysis licencing guidelines’
2. Gender a. Malea b. Female • To increase clinical face validity • To examine if gender has an unconscious influence on decision-making
3. Age a. 68a b. 85 c. 95 • Included for purposes of ecological and face validity • Evidence from exploratory work that some clinicians may take patient age into account and adhere to current licensing guidelines
4. Frailty a. you do not perceive as fraila b. you perceive as frail • Very challenging to adequately define frailty due to subjectivity in how clinicians view/consider it • Aim was to trigger perception of frailty in patient and therefore the current phrasing was considered optimal to meet aim
5. Time since symptom onset a. 50 mina b. 2 h 30 mins c. 4 h 15 mins • Potential greater benefit of very early treatment time (50 mins) included to compare to mid-point in time window and rapidly approaching end of window (4 h 15mins)
6. Pre-stroke dependency (mRS) a. mRS 1 b. mRS 3 c. mRS 4a • Qualitative work suggested mRS 3 was the grey area in dependency
7. Pre-stroke cognitive functioning a. No history of memory problemsa b. Moderate dementia c. Severe dementia • Exploratory work suggested dementia/cognitive functioning could influence decision to offer thrombolysis
8. Ethnicity a. whitea b. Afro-Caribbean c. Asian • Included as an attribute that may have an implicit effect on decision-making • Included as this is information that would be obvious in a typical decision
9. NIHSS (stroke severity) a. NIHSS 2 (without aphasia)a b. NIHSS 2 (with aphasia) c. NIHSS 5 (without aphasia) d. NIHSS 5 (with aphasia) e. NIHSS 14a f. NIHSS 23 • Presence or absence of aphasia deemed very important in previous stage and therefore was included at lower NIHSS scores (mild strokes) to assess whether it would influence decision-making. • NIHSS 14 included as it is the SITS mean score (for treated patients) • NIHSS 23 considered a severe stroke
  1. areference category