Table 1.

Recruitment strategies and number of general practitioners recruited for this study.

Recruitment strategy		Number of GPs recruited
Probability sampling
	Direct invitation to GP (postal invitations were sent to 25 practices in Cambridgeshire, which were then followed up by phone calls. A primary care research network [PCRN] also sent a letter on our behalf inviting and promoting the study to research active GPs and practices in Coventry)	1
	Invitation through practice managers (phone calls were made to 25 GP practice managers in Cambridge and a follow-up email was also sent; 13 further GP practices were then contacted through phone and then fax)	2
	Promoting study in email-based GP newsletters (the study was promoted in the following GP newsletters: Cambridgeshire NHS Newsletter, Lewisham Weekly Newsletter, Lambeth PCT newsletter, South NHS North West London Newsletter, Participate Autumn Magazine)	3
Snowball sampling
	Email to acquaintances with potential GP contacts	1
	Twitter call out to acquaintances with potential GP contacts	0
	GPs emailing their GP acquaintances	5
	Medical doctors phone calling their GP acquaintances	8
Total		20