Methods
Design, Study Population and Sampling Technique
A qualitative, interview-based, study was designed. The study population of interest was people who had purchased a home BP monitor for their own use. Those who had been provided with a monitor through their healthcare provider (e.g. the UK National Health Service - NHS) were thus excluded. We then purposefully selected participants to provide maximum variation in relation to the health condition that triggered the device purchase.
Setting and Recruitment Strategy
Prospective participants were recruited through advertisements placed at a UK University in North West London and the local community (i.e. Uxbridge). Pharmacies were also approached but adverts were not feasible to be placed at these sites. Additional participants were further recruited through the researchers' personal networks (see Table 1).
Most interviewees were residents of London, and fewer were living in other areas in England (i.e. Nottingham, Milton Keynes, and Alton). People who expressed an interest in the research completed initially a short questionnaire (Additional file 1) which ensured eligibility for participation. The screening questionnaire also included questions about participants' demographics, the self-reported health condition that prompted the device purchase (see Table 2), as well as the characteristics of the monitor (see Table 3) and its use (e.g. duration, frequency).
Data Collection
Twenty-one people initially expressed an interest in the study of whom 18 were eligible. Eligible participants were invited to take part in a face-to-face, semi-structured interview which was conducted in line with the designed interview protocol (Additional file 2). Participants were informed about the purpose and the procedure of the interview and provided written consent. Interviews were carried out by KV between January and April 2012 and were recorded. At the end, participants were fully briefed and were given a £15 voucher in acknowledgement of their participation. Ethical approval was granted from the Ethics Committee of Brunel University, London.
Data Analysis
Recorded interviews were transcribed verbatim by a professional company. Scripts were subjected to thematic analysis, a suitable analytic technique for the identification of 'repeated patterns of meaning'. The analysis proceeded as follows: initially there was a familiarisation process through the repeated reading of transcripts that facilitated immersion in the data. Data relevant to our research questions were noted. Next, extracts of similar meaning were assigned to developing codes, assisted by computer software (NVivo 9). No new codes were identified after the twelfth interview indicating data saturation. Semantically-related codes were then grouped together and themes and subthemes were developed. Initial coding was applied by KV, and themes and subthemes were developed, revised and refined in conjunction with JB in regular meetings.