Table 1 First modification to the recruitment strategy, including the rationale and evidence for the chosen strategy

GP to mention study at the end of a consultation, print out invitation letter and give to patient or arrange for the letter to be sent in the post by practice administrators.

MODIFIED to

In addition to GP/Nurse recruiting during consultation, practice managers will generate a list of patients that have presented with sleeping difficulties in the previous 3 months and practice managers to send out the invitation letters to them on behalf of the GP.

It was not working.

It was possible that GPs were acting as gatekeepers.

It was possible that GPs/Nurses under the pressure of the consultation were forgetting to discuss the study.

It was possible that GPs/Nurses felt that directly mentioning research was intruding on the doctor patient relationship.

It was possible that we had just overestimated our recruitment potential.

Studies that required the GP to be alert during consultations were less successful.

When GP or practice assistant was the first to inform the patient about the study, patient recruitment was less successful than when the patient received a letter by mail.[65]

Not enough time during consultation - impact on working practices. [11, 25, 66–69]

Participation by clinicians in randomised controlled trials was deterred by concern over the doctor-patient relationship.[32]

Clinicians who had recruited reported 'trials involve extra work' and 'inviting patients to participate is embarrassing'-these factors affect clinicians' willingness to invite patients to participate.[32]

Lasagna's Law (over-optimistic recruitment prediction) holds in Dutch primary care research.[70]

Posters displayed in the surgery waiting area inviting patients who have recently consulted their GP with sleeping difficulties to take part in the study by asking them to speak to their GP.

Aspect of recruitment subsequently modified

We wanted patients to know about the study if it applied to them.

To mention it to friends and relatives to whom it might apply.

To prepare them to be receptive to the study if the GP discussed it with them.

To give patients a chance to be proactive in the recruitment to the study.

With regards to trials in primary care recruitment, a strategy frequently used is waiting room posters informing patients that a study is in progress and targeted poster campaigns to encourage recruitment.[38, 57, 71, 72]