'Predictors of expectations and requests for antibiotics in primary care'
(AsPredicted #5480)

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1) Have any data been collected for this study already?
No, no data have been collected for this study yet.

2) What's the main question being asked or hypothesis being tested in this study?
We aim to better understand patient expectations and requests for antibiotics. Specifically, we are interested in which dimensions of illness perception, antibiotic beliefs, attitudes and knowledge, are most predictive of antibiotic expectations and requests in primary care.
We predict that there will be a relationship between pre-existing knowledge, attitudes, and beliefs about antibiotics and expectations and requests for antibiotics. Essentially, we expect that increased erroneous knowledge, attitudes, and beliefs about antibiotics will be positively associated with increased expectations and requests.
We also predict a relationship between pre-existing perceptions of a specific upper respiratory tract infection (URTI) and expectations and requests for antibiotics, such that increased erroneous perceptions will be positively associated with increased expectations and requests.
Additionally, we expect that prescribing history for viral and bacterial infections will be associated with expectations and requests for antibiotics. Increased frequency of prescribing histories of antibiotics for both viral and bacterial infections are expected to be associated with increased expectations and requests for antibiotics.

3) Describe the key dependent variable(s) specifying how they will be measured.
Expectations for antibiotics: average of 4 items measured on a 6-point scale (1 = Strongly disagree to 6 = Strongly agree) – assuming sufficient internal consistency
Expectations of doctors prescribing behaviours: average of 4 items measured on a 6-point scale (1 = Strongly disagree to 6 = Strongly agree) – assuming sufficient internal consistency
Requests for antibiotics: average of 4 items measured on a 6-point scale (1 = I certainly would not to 6 = I certainly would) – assuming sufficient internal consistency

4) How many and which conditions will participants be assigned to?
This will be a correlational study where participants will not be assigned to separate conditions. However, the presentation order of the dependent variables (DVs) and the questionnaires will be randomised.
We will randomise the presentation order of the DVs to be displayed to participants either before the questionnaires or after. The order of presentation for the two questionnaires (one on beliefs, attitudes and knowledge about antibiotics, and the other on perceptions of a specific upper respiratory tract infection: the common cold) will also be randomised as will the order of the items within each questionnaire.

5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
We will run correlation matrices between the different dimensions of illness beliefs (Severity, timeline, consequences, personal control, treatment control, illness coherence, timeline cyclical, emotional representations and causes), antibiotic beliefs (knowledge of efficacy, knowledge of appropriate use, knowledge of resistance, anticipated regret, trust of appropriate prescribing, subjective social norms, descriptive social norms, self-efficacy, expected positive health outcomes, awareness of side effects, summary attitudes towards antibiotics, and subjective probabilities of positive and negative outcomes), prescription history (for viral infections and for bacterial infections) expectations for antibiotics, expectations of doctors prescribing behaviours and requests for antibiotics.
We will also run multiple regression models to estimate the predictive relationships of pre-existing concepts of antibiotics and a specific URTI, as well as prescribing history (as listed above), on (i) expectations for antibiotics, (ii) expectations of doctors prescribing behaviour, and (iii) requests for antibiotics.
Items in the antibiotics questionnaire and the illness perception questionnaire will be subjected to exploratory factor analysis.

6) Any secondary analyses?
An equivalent default Bayesian analyses for the correlations and multiple regression will be carried out as well to quantify support for the models assumed by the null and alternative hypotheses.
We will analyse whether age, gender, income, employment, ethnicity/race, education, and typical consultation behaviour moderates these relationships.

7) How many observations will be collected or what will determine sample size?
No need to justify decision, but be precise about exactly how the number will be determined.
We aim to reach 400 participants. The data collection will finish once we reach the sample size (not accounting for the exclusion criteria outlined below).

8) Anything else you would like to pre-register?
(e.g., data exclusions, variables collected for exploratory purposes, unusual analyses planned?)
(i) Participants who complete the questionnaire in a very short time (1/3 of median time estimated at the time of this pre-registration as around 3 minutes) will be excluded.
(ii) Participants who do not complete the questionnaire fully (fully = seeing the debrief screen) will be excluded.
(iii) Participants who complete the questionnaire in a very long time (more than 2 hours – based on completion rates of a similar study) will be excluded.
(iv) Participants who fail to correctly respond to at least 4 out of 7 instructed bogus questions.

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