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Trial registered on ANZCTR
Registration number
ACTRN12625001103459p
Ethics application status
Submitted, not yet approved
Date submitted
17/09/2025
Date registered
9/10/2025
Date last updated
9/10/2025
Date data sharing statement initially provided
9/10/2025
Type of registration
Prospectively registered
Titles & IDs
Public title
Impact of carbon footprint information on inhaler prescribing intentions by general practitioners: an online factorial randomised experiment
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Scientific title
Impact of carbon footprint information on inhaler prescribing intentions by general practitioners: an online factorial randomised experiment
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Secondary ID [1]
315209
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None
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Universal Trial Number (UTN)
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Trial acronym
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Linked study record
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Health condition
Health condition(s) or problem(s) studied:
Asthma
338659
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Condition category
Condition code
Respiratory
334951
334951
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0
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Asthma
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Public Health
334952
334952
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0
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Health service research
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Intervention/exposure
Study type
Interventional
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Description of intervention(s) / exposure
Directly after randomisation, all participants will receive an online hypothetical scenario for them to read through. This is part of the online survey administered through Qualtrics and is estimated to take 2-5 minutes to read. The interventions are delivered by the study researchers through Qualtrics, each participant will be randomised to one of four interventions (2x2 factorial) or a control scenario. The randomised intervention (or control) will be delivered once only to each participant and will occur online. Qualtrics will record how much time participants spend on the page, which we can use as a proxy to monitor adherence (i.e. if participants had enough time to read through the allocated scenario). there is no "back" button included in the online survey, hence, participants cannot go back to be re-allocated to a different scenario.
Our baseline clinical scenario reflects a usual GP consultation for a hypothetical, adult middle-aged female with mild to moderate but poorly controlled asthma. Participants will be asked to imagine that for this patient, they had previously prescribed a dry powder inhaler (DPI), low-dose inhaled corticosteroid (ICS)-containing preventer and a pressurised metered dose (pMDI) short-acting beta2-agonist (SABA) reliever, and that she reported regular use of this reliever without a spacer and irregular use of the preventer inhaler. They are then informed that they decide to recommend the patient trial maintenance and reliever therapy (MART) with an anti-inflammatory reliever (ICS-formoterol inhaler), as per the newly revised Australian Asthma Guidelines. They explain this approach to the patient, check the patient’s inhaler technique is adequate for both types of devices, establish that both inhaler types incur the same out-of-pocket cost to the patient and that she has no preference for inhaler type but is asking for the GP’s recommendation.
The four possible intervention arms that participants can be randomised to are:
A. Collective impact / with graphic (factor 2, level 0): additional information on differences in environmental impacts from prescribing different types of inhalers to all similar patients from five GPs over one year with graphic display: additional information on the carbon footprint of one DPI versus one pMDI, the carbon emission savings in kg CO2e emissions for prescribing a DPI instead of pMDI for 200 similar patients (5 GPs with 40 patients each) over one year, and the private car journey distance this is equivalent to. Plus an additional graphic display of the annual potential differences in carbon footprint. This comprises bar charts comparing the carbon savings in CO2e emissions to the impact of six other potential emissions-reducing behaviour changes to give participants some perspective around the meaning of the carbon footprint.
B. Single impact/ with graphic (factor 2, level 1): additional information on differences in environmental impacts from prescribing different types of inhalers to the one patient with graphic display: additional information on the carbon footprint of one DPI versus one pMDI, the carbon emission savings in kg CO2e emissions for prescribing a DPI instead of pMDI for one patient over one year, and the private car journey distance this is equivalent to. Plus an additional graphic display of the annual potential differences in carbon footprint. This comprises bar charts comparing the carbon savings in CO2e emissions to the impact of six other potential emissions-reducing behaviour changes to give participants some perspective around the meaning of the carbon footprint.
C. Collective impact / no graphic (factor 1, level 1): additional information on differences in environmental impacts from prescribing different types of inhalers to all similar patients from five GPs over one year without graphic display: additional information on the carbon footprint of one DPI versus one pMDI, the carbon emission savings in kg CO2e emissions for prescribing a DPI instead of pMDI for 200 similar patients (5 GPs with 40 patients each) over one year, and the private car journey distance this is equivalent to.
D. Single impact / no graphic (factor 1, level 0): additional information on differences in environmental impacts from prescribing different types of inhalers to the one patient without graphic display: additional information on the carbon footprint of one DPI versus one pMDI, the carbon emission savings in kg CO2e emissions for prescribing a DPI instead of pMDI for one patient over one year, and the private car journey distance this is equivalent to.
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Intervention code [1]
331823
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Behaviour
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Comparator / control treatment
E. Control: Basic clinical information on patient and inhaler choices, no environmental information provided
Our baseline clinical scenario reflects a usual GP consultation for a hypothetical, adult middle-aged female with mild to moderate but poorly controlled asthma. Participants will be asked to imagine that for this patient, they had previously prescribed a dry powder, low-dose ICS-containing preventer and a pressurised metered dose SABA reliever, and that she reported regular use of this reliever without a spacer and irregular use of the preventer inhaler. They are then told that they decide to recommend the patient trial maintenance and reliever therapy (MART) with an anti-inflammatory reliever (ICS-formoterol inhaler), as per the newly revised Australian Asthma Guidelines. They explain this approach to the patient, check the patient’s inhaler technique is adequate for both types of devices, establish that both inhaler types incur the same out-of-pocket cost to the patient and that she has no preference for inhaler type but is asking for the GP’s recommendation. Participants randomised to the control group receive no further information.
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Control group
Active
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Outcomes
Primary outcome [1]
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GP inhaler type recommendation
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Assessment method [1]
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Proportion of GPs recommending pressurised metred dose (pMDI) inhaler vs dry powder inhaler (DPI). The primary outcome is participants’ recommendation for the hypothetical patient: DPI versus pMDI. In Australia, currently eight different inhalers are subsidised and listed for MART on the pharmaceutical benefits scheme (PBS). To force a binary choice and make options as similar as possible apart from inhaler type (DPI vs pMDI), we chose the Symbicort Turbuhaler as the DPI option versus the Symbicort Rapihaler as the pMDI option. Participants will be asked directly after reading through their allocated scenario: "Which inhaler would you recommend the patient tries first?" (Answer options: Symbicort Rapihaler or Symbicort Turbuhaler) This question is accompanied by a small table that shows a picture of each of the available two inhalers, specifies the inhaler type (pMDI or DPI), strength, maintenance dose, reliever dose, number of inhalers dispensed per script and cost per script to patient.
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Timepoint [1]
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Directly after presentation of scenario
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Secondary outcome [1]
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Participant confidence in clinical decision making
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Assessment method [1]
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Single-question item using a 5-point Likert scale “How confident are you in your decision?” (1= not at all confident; 5 = extremely confident)
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Timepoint [1]
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Directly after scenario presentation
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Secondary outcome [2]
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Management choice anxiety
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Assessment method [2]
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Single-question item using a 5-point Likert scale “After making this treatment choice, how anxious do you feel about potential adverse outcomes for the patient?” (1= not at all anxious; 5 = extremely anxious )
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Timepoint [2]
451529
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Directly after scenario presentation
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Secondary outcome [3]
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Acceptability of information
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Assessment method [3]
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Single-question item using a 5-point Likert scale “How strongly do you agree with the following statement: ‘I would give this information to other GPs if they wanted to know more about inhaler device types.’” (1 = strongly disagree, 5 = strongly agree)
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Timepoint [3]
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Directly after scenario presentation
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Secondary outcome [4]
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Trustworthiness of information
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Assessment method [4]
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Single-question item using a 5-point Likert scale “How strongly do you agree with the following statement: ‘I find the information provided trustworthy.’?” (1= strongly disagree; 5=strongly agree)
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Timepoint [4]
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Directly after scenario presentation
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Secondary outcome [5]
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Other steps that participants would potentially consider initiating for patient treatment.
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Assessment method [5]
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Single-item with free-text input: "Are there any other management actions you would initiate for this patient at this visit?"
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Timepoint [5]
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Directly after scenario presentation
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Secondary outcome [6]
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Explanation of choice
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Assessment method [6]
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Single-item with free-text input: "Why did you choose this inhaler?”
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Timepoint [6]
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Directly after scenario presentation
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Eligibility
Key inclusion criteria
We are seeking participants who are currently accredited and practicing as General Practitioners (GPs) in Australia. To be able to complete the survey participants must be able to understand written English.
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Minimum age
18
Years
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Maximum age
No limit
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Sex
Both males and females
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Can healthy volunteers participate?
Yes
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Key exclusion criteria
Anyone who is not currently a practicing GP in Australia and/or who is not able to understand written English is ineligible to participate.
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Study design
Purpose of the study
Educational / counselling / training
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Allocation to intervention
Randomised controlled trial
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Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Eligible participants will undergo central randomisation to groups by Qualtrics survey software after providing consent. Allocation to groups will be concealed from participants and investigators.
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Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Qualtrics uses the Mersenne Twister pseudorandom number generator for randomisation.
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Masking / blinding
Open (masking not used)
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Who is / are masked / blinded?
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Intervention assignment
Factorial
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Other design features
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Phase
Not Applicable
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Type of endpoint/s
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Statistical methods / analysis
All analyses will use an intention to treat approach, with participants analysed in the groups they were randomised to. The primary and secondary outcomes will be compared pairwise across randomised factorial groups using a superiority framework with a factorial (at-the-margins) analysis approach pre-specified. For this, we assume that there are no interactions between interventions (factors) – however, we will assess this.
Our primary analyses will focus on assessing the total average effect of receiving environmental information in any form compared to control (groups A-D vs group E). In secondary analyses we will then explore the impact of two approaches to communicating the carbon footprint differences in inhaler types on prescribing preferences: single versus collective action (B+D against A+C); and graphic versus no graphic provided (A+B against C+D).
Furthermore, we will investigate differences in outcomes between the following groups: only receiving environmental information, in the absence of both factors (group D); receiving only the collective action intervention, in the absence of factor 2 (group C); receiving only the graphic display intervention in the absence of factor 1; (group B) receiving both interventions (group A); and the control (group E). We will also assess potential interaction effects between the two intervention factors. The power to detect differences in these pairwise comparisons and interactions will depend on the effect sizes and smaller effects may go undetected. However, this exploratory analysis will enable the detection of larger effects and generate hypothesises for future investigation.
We will summarise outcome variables and covariates using counts and percentages for categorical data and mean and SD, median and quartiles, and minimum and maximum for continuous data. We will present the number of participant responses included in the analysis for each outcome.
We will build logistic regression models for binary outcomes and linear regression models for continuous outcomes. All hypothesis tests will be two-sided with an a of 5%. We will calculate unadjusted and adjusted effect estimates with adjustment for baseline characteristics (potential confounders), variables used in the stratified sampling and a term for the factor not of interest for each comparison (e.g. factor 2 for comparison 1). The potential for participants’ demographics (age, gender, country of birth, location), clinical experience (years of GP experience and number of asthma consultations) and climate change concern to act as effect modifiers will also be explored. All quantitative data analysis will be conducted in SAS.
We will use content analysis to summarise themes in the two free text responses.
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Recruitment
Recruitment status
Not yet recruiting
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Date of first participant enrolment
Anticipated
3/11/2025
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Actual
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Date of last participant enrolment
Anticipated
1/12/2025
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Actual
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Date of last data collection
Anticipated
1/12/2025
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Actual
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Sample size
Target
250
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Accrual to date
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Final
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Recruitment in Australia
Recruitment state(s)
ACT,NSW,NT,QLD,SA,TAS,WA,VIC
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Funding & Sponsors
Funding source category [1]
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Government body
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Name [1]
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National Health and Medical Research Council (NHMRC)
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Address [1]
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Country [1]
319770
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Australia
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Primary sponsor type
Individual
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Name
Luise Kazda, The University of Sydney
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Address
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Country
Australia
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Secondary sponsor category [1]
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Individual
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Name [1]
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Katy Bell, The University of Sydney
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Address [1]
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Country [1]
322278
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Australia
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Ethics approval
Ethics application status
Submitted, not yet approved
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Ethics committee name [1]
318329
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The University of Sydney Human Research Ethics Committee
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Ethics committee address [1]
318329
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https://www.sydney.edu.au/research/research-integrity-and-ethics.html
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Ethics committee country [1]
318329
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Australia
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Date submitted for ethics approval [1]
318329
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08/09/2025
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Approval date [1]
318329
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Ethics approval number [1]
318329
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Summary
Brief summary
Many asthma patients experience suboptimal disease control and are disproportionally impacted by worsening environmental risk factors due to climate change. General practitioners (GPs) are well-placed and trusted to lead conversations to improve asthma management. The resulting treatment improvements have the potential to simultaneously reduce the significant greenhouse gas emissions from inhalers as a co-benefit. This study aims to explore whether adding environmental impact information for respiratory inhalers can influence clinician prescribing while improving quality of care and investigates optimal ways to communicate environmental impacts to GPs. We will conduct a factorial (2×2 pus control) randomised online hypothetical experiment with Australian GPs. Following consent and baseline information on guideline-concordant maintenance-and-reliever-therapy (“MART”) prescribing, participants will be randomised 1:1:1:1:1 to five conditions: A. Emissions impact: collective action / with graphic; B. Emissions impact: single-action / with graphic; C. Emissions impact: collective action / no graphic; D. Emission impact: single-action / no graphic; E. Control: no further information. The required sample size is 250 GPs. The primary outcome is participant choice of inhaler type (dry powder or pressurised metered dose). Secondary outcomes include participant level of confidence in their choice, management choice anxiety, acceptability and trustworthiness of information received and reasons for inhaler choice. This study will provide evidence on whether and how environmental impact information can influence prescribing intentions among GPs. Findings will inform future interventions aimed at aligning clinical and environmental goals in respiratory care. The results of the study will be published in a peer-reviewed journal and a lay summary of the findings will be published on the Wiser Healthcare Research Collaboration and Healthy Environments and Lives (HEAL) Network publications pages.
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Trial website
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Trial related presentations / publications
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Public notes
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Contacts
Principal investigator
Name
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Dr Luise Kazda
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Address
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Room 101, Edward Ford Building (A27), Fisher Road, Sydney School of Public Health, The University of Sydney, NSW 2006
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Country
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Australia
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Phone
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+61 02935 14823
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Fax
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Email
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[email protected]
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Contact person for public queries
Name
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Luise Kazda
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Address
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Room 101, Edward Ford Building (A27), Fisher Road, Sydney School of Public Health, The University of Sydney, NSW 2006
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Country
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Australia
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Phone
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+61 02935 14823
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Fax
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Email
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[email protected]
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Contact person for scientific queries
Name
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Luise Kazda
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Address
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Room 101, Edward Ford Building (A27), Fisher Road, Sydney School of Public Health, The University of Sydney, NSW 2006
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Country
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Australia
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Phone
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+61 02935 14823
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Fax
143828
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Email
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[email protected]
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Data sharing statement
Will the study consider sharing individual participant data?
Yes
Will there be any conditions when requesting access to individual participant data?
Persons/groups eligible to request access:
•
Researchers
Conditions for requesting access:
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No requirements
What individual participant data might be shared?
•
All de-identified individual participant data
What types of analyses could be done with individual participant data?
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Any type of analysis (i.e. no restrictions on data re-use)
When can requests for individual participant data be made (start and end dates)?
From:
After publication of main results
To:
No end date
Where can requests to access individual participant data be made, or data be obtained directly?
•
Email of trial custodian, sponsor or committee:
Email to CI:
[email protected]
Are there extra considerations when requesting access to individual participant data?
No
What supporting documents are/will be available?
No Supporting Document Provided
Results publications and other study-related documents
Documents added manually
No documents have been uploaded by study researchers.
Documents added automatically
No additional documents have been identified.
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