Study design
This cross-sectional, observational study was part of a larger mixed-methods project (41). Data were collected via online questionnaires. This paper presents the data collected with the PABS-PT (41).
Participants
Clinicians were eligible to participate if they were registered and practising in New Zealand as either a physiotherapist or GP, had treated a patient with hip and/or knee osteoarthritis in the past six months, were living in New Zealand at the time of data collection and had sufficient English language skills to complete the survey.
Measures/questionnaires
The survey comprised two sections: 1) demographic and occupational characteristics and 2) beliefs about hip and/or knee joint osteoarthritis (adapted PABS-PT). Demographic and occupational characteristics data included participants’ sex, age, duration of practice and geographical location of practice.
The PABS-PT was originally designed to collect physiotherapists’ beliefs about the treatment of LBP (35). Since then, the measure has been adapted for use by both GPs and physiotherapists (37), including to measure beliefs about neck pain (40). The present study used the original version of the questionnaire, which comprises 20 items that are scored on a six-point Likert scale (totally disagree to totally agree) (35). The questionnaire has a two-factor structure. One factor is labelled biomedical (14 items) and the other behavioural (6 items). For this study, the questionnaire was adapted so that any reference to LBP was replaced with ‘osteoarthritis’. Examples of items are: ‘Pain caused by osteoarthritis indicates the presence of organic injury’ and ‘The cause of osteoarthritic pain is unknown’.
Procedure
Before the survey was administered, all questions were tested for face validity and readability. Three researchers with experience in osteoarthritis research and survey design read the questionnaire and provided feedback about survey length, appropriateness for the New Zealand context and readability. The fully anonymised survey was advertised through several channels: physiotherapy continuing education courses; the Physiotherapy New Zealand Conference; Physiotherapy New Zealand and The Royal New Zealand College of General Practitioners e-newsletters; and the local primary healthcare organisation. Data were collected between 1 September and 1 December 2016 via SurveyMonkey (https://www.surveymonkey.com). Participants were required to read the online participant information sheet and respond to the items in the questionnaire. No identifying information was collected, and participants could not be identified or traced.
Data analysis
All data were analysed using SPSS version 24.0 (IBM, USA), with the alpha level set at p < 0.05. Missing data were limited by the use of the online platform because participants were directed by automatic prompts to complete any missed item or question. Only complete data sets were analysed. It was not possible to calculate a total return rate for the survey as participants completed the study online, and it was unknown how many potential participants saw the study advertisement but chose not to participate.
Demographic and occupational characteristics
All data describing demographic and professional characteristics were categorical. For each category, the total number of scores was described using descriptive statistics. Data from GPs and physiotherapists were presented together and separately to allow comparison between the two professions. Categories that represented a small number of participants were collapsed into a single category, called ‘Other’. Group equivalency between the two professions for demographic and occupational characteristics data were assessed with chi-square tests (42). The Yates correction for continuity was reported where data were represented as a two-by-two assessment (42).
Factor structure of the Adapted PABS-PT
Means and standard deviations were calculated to show the response distribution of the data for each item in the Adapted PABS-PT. The correlation matrix was then calculated and screened to ensure the presence of correlations of 0.3 or greater, and to determine if the sample was suitable for principal component analysis. The data were subjected to the Kaiser-Meyer-Olkin measure of sampling adequacy and Bartlett’s test of sphericity, and principal component extraction was performed. On the basis of the Scree test, which was consistent with the number of factors reported by Ostelo et al. (35), the criteria were limited to a two-factor solution, and the eigenvalues for each factor were plotted. Varimax rotation was applied because it typically produces clear and interpretable solutions, and it would allow ready comparison with the findings of Ostelo et al. (35). For clarity, factor loadings of 0.45 or lower were concealed. Next, each subscale (factor) was named, and its internal consistency examined by calculating the Cronbach’s alpha. Where appropriate, the names of subscales matched those proposed by Ostelo et al. (35). The subscale was described as having acceptable internal consistency when the included items made conceptual sense and had a Cronbach’s alpha ≥0.7. Finally, group mean scores and standard deviations were calculated for each subscale.
Ethical considerations
This study was granted ethical consent by the relevant Institutional Ethics Committee on 11 August 2016 (AUTEC: 16/284). There was no mechanism of identifying people who participated in the study and the participant information explained that by submitting the questionnaire electronically, they were consenting for the data to be used for the study.