Type of funding received for the research

Key recruitment theme(s) contained within the article.

Articles have been assigned to one of the following categories based on the type of recruitment evidence.

Evaluation: The formal assessment of the effectiveness of a recruitment strategy through a nested randomised control trial, a case control or a systematic review.

Application: Information on the use of a recruitment strategy without formal evaluation. This includes informal evaluations such as level of recruitment before and after a strategy is applied and hypothetical models of recruitment strategies.

Observation: Concepts, observations or information that may be used to develop recruitment strategies. This includes lessons learnt from trials and reasons for participation/ non participation.

A brief summary of the intervention/ strategy that is being evaluated. Please note this category has only been completed for randomised evaluations of strategies.

A brief summary of the findings of the research. Please note this category has only been completed for randomised evaluations of strategies.

The research methods used to evaluate recruitment such as a nested randomised control trial, a survey of participants or a case report sharing lessons learnt from a health research study.

The outcomes used to evaluate recruitment. For the database 'Recruitment rate' is defined as the number of patients recruited per month or year. 'Representativeness' looks at the diversity of research participants compared to the general population or condition population. 'Numbers recruited' also includes the percentage of patients recruited from screening.

Often recruitment research is conducted in preparation for or during a health research study. This category indicates when the recruitment research was undertaken in relation to the health research. e.g. during the feasibility, during an ongoing study.

Key retention theme(s) contained within the article.

Articles have been assigned to one of the following categories based on the type of evidence.

Randomised Evaluation: A planned assessment of the effectiveness of a strategy through a nested randomised control trial.

Non-randomised evaluation: A planned assessment of a strategy using a pre-post test, case control or other non-randomised design. This also includes qualitative evaluation.

Application: Studies describing the use of a strategy without comparative evaluation.

Observation: Concepts, observations or information that may be used to develop strategies. This includes lessons learnt from studies.

A brief summary of the intervention/ strategy that is being evaluated. Please note this category has only been completed for randomised evaluations of strategies.

A brief summary of the findings of the research. Please note this category has only been completed for randomised evaluations of strategies.

The research methods used to evaluate retention such as a nested randomised control trial, a survey of participants or a case report sharing lessons learnt from a health research study.

The outcomes used to evaluate retention. For the database 'Retention rate' covers assessment of participant retention and/ or levels of missing data. 'Representativeness' looks at the diversity of research participants who are retained or return outcome data.

Often retention research is conducted in preparation for or during a health research study. This category indicates when the recruitment research was undertaken in relation to the health research. e.g. during the feasibility, during an ongoing study.

The design of the health research study to which patients are being recruited e.g. cohort study, interview or a survey. Randomised control trials have been split into different categories. RCT is used for parallel trials or where there is no further information on the trial design. Where more specific information is available trials have been categorised as Cluster RCT, Crossover RCT, Factorial RCT or Patient Preference.

A list of all the continents where the research was conducted and patients were recruited.

Information on who was blind to the treatment allocation. The gender of patients recruited to the study. Where articles report more than one study all relevant categories have been chosen.

Type of approach used to recruit participants . A 'direct' approach is defined as approaching patients who are known or highly likely to meet eligibility criteria. Indirect approaches such as newspaper advertising target broader audiences of whom only some will be eligible.

The healthcare setting where patients are recruited. For mailing lists we have taken into account where the lists were generated and/ or where final consent conversations were undertaken.

The Health Research Classification System (HRCS) category for the patient's condition and/ or health research.

This free text field gives more specific information on the health area e.g. HIV.

The type of health intervention patients receive e.g. a drug, surgical procedure or medical device

The aim of the health intervention e.g. treatment or prevention.

The healthcare setting where the treatment intervention is given and / or monitored.

The different types of outcome data collected in the health research study e.g. questionnaires, interview, clinical measure, samples

Where the outcome data is obtained. e.g Home (returned by post, email or over the phone), Online (e.g via a website or online app), Clinic visit or Electronic Health record (EHR). Data recorded in a participants home but returned during a visit to the study site would be categorised as Clinic Visit.

The age range of patients. Where possible we have based this on the patient eligibility criteria. However, in some cases we have had to use the baseline characteristics of participants to identify likely categories.

The gender of patients recruited to the study. Where articles report more than one study all relevant categories have been chosen.