Projection of participant recruitment to primary care research

Background Recruitment to clinical trials remains challenging, particularly in primary care settings. Initial projections of participant recruitment should be as accurate as possible, in order to avoid the financial, clinical and ethical costs of trial extensions or failures. However, estimation of recruitment rates is challenging and often poorly executed. We used qualitative methods to explore the experiences and views of researchers on the planning of recruitment in this setting.

The manuscript is well written and approaches the topic from an interesting perspective. The complexity involved in recruitment projection is an area which requires more thought by those involved in commissioning and design of trials. The study explores the factors which influence issues in primary care -a really interesting point about GPs specialising within a practice (and perhaps in research itself) which can skew calculations and interest from staff and potential participants. The manuscript builds on existing knowledge and highlights the need for appropriate methods and greater availability of data to improve projections.

Major Compulsory Revisions
None.
Minor Essential revisions -Identify the role of the interviewee quoted i.e. investigator/ study manager. I feel this is the most important characteristic of the sample.
-Interviewer's current occupation and gender should be explicit in the methods section.
-Theoretical framework underpinning the study is implied by the method chosen for data analysis but not explicitly explored in the methods section.
Discretionary Revisions -Background para. 3 -a reference for the claim that primary care does not have an established research culture.
-Methods (sampling para. 2) -14 invitations were made -is this the whole population as a result of the CLRN search (and studies known to the study team)? If not, you mention the characteristics for the purposive sample but justifying the number selected or stating the total number of relevant studies from which you sampled would be useful.
-Results -Due to a limited number of quotes it was difficult, in parts of the results section, to understand the strength of opinion; although, I appreciate it is a small sample.
-Results (2.1 Qualitative work) -I'm not sure how this theme relates to the research question. I recommend adding more detail; and if possible, a relevant quote to illustrate the results intended.
Discussion -There is acknowledgment by the authors that interviewing proposal developers would have enriched the research. I agree that this perspective would have been very useful. Further details about the characteristics of the study (e.g. funder) and interviewees (e.g. the extent to which they were involved in the recruitment projections for the reference study they discussed) could be added. This would add context to their views. For example, a study manager who was not involved at the planning stage but has to implement the project plan and accrual projections may have a different perspective to a proposal developer that has had to produce the projections but is more removed from delivery. There are some statements in the results but you could also include the range of funding bodies and size of studies if you can't add per-case details. The non-commercial nature of the research is not stated until the strength and limitations (unless I missed it!).
-There is a potential policy implication for funding bodies which could be explored. The manuscript demonstrates the complexity involved and that limited data are available resulting in poor projections and extensions. Funders often require recruitment projections and timelines but allow little or no room for contingency in applications. Furthermore, funders do not insist on a consistent method which could drive improvements in availability of data and methodology.
-The UKCRN has reorganised which impacted on the PCRN -this may have occurred after the time of writing but if not may be a point for discussion.
Level of interest:An article whose findings are important to those with closely related research interests Quality of written English:Acceptable Statistical review:No, the manuscript does not need to be seen by a statistician.

Declaration of competing interests:
I work for the same organisation (and Clinical Trials Unit) as the authors for which I receive a salary. I have published with Dr Daniel Hind in the past; however, I have played no role in the conduct or writing up of this paper.