Table 1

Key characteristics, summary of findings and quality assessment of included studies

Author, year	Host RCT	Host RCT therapeutic area	Recruitment stage studied	Recruitment study design	Screened/eligible /randomised* (n)	Intervention(s)	Summary of findings	Quality assessment†
Bhar et al, 201338	Not specified	Suicide prevention	Identification of participants	Quantitative descriptive	233/48/33	Various mass mailing and health service referral strategies.	Seeking referrals from a co-investigator’s clinic was the most effective strategy and also had the highest uptake rate. Seeking referrals from non-collaborating health services and mass mailings were not effective strategies.	Fair
Cauley et al, 201539	T trials	Low testosterone treatment	Identification of participants	Quantitative descriptive	51,085/931/790	Various mass mailing, media and community outreach strategies.	Mass mailing was the most effective recruitment strategy and was also the lowest cost per man screened. TV, radio and print advertisements, clinicaltrials.gov listing, posters and flyers and presentations at events resulted in very few men being screened.	Poor
Chlebowski et al, 201040	SELECT	Prostate cancer prevention	Identification of participants	Quantitative descriptive	4022/NR/634	Mailing to male home owners vs mailing to previous female research participant spouses.	Mailing previous female research participants' spouses resulted in higher recruitment uptake than mailing men and was also more cost-effective. Mailing women contributed fewer participants than mailing men due to the relatively small size of the past research participant mailing list.	Fair
Cook et al, 201041	SELECT	Prostate cancer prevention	Identification of participants	Non-randomised controlled trial	NR/NR/8532	Various site-directed minority-targeted recruitment strategies funded by minority recruitment enhancement grants.	Sites awarded grants increased recruitment of African-American men significantly more than matched comparison sites. Overall recruitment was also increased at grant sites.	Poor
Heiney et al, 201042	EASE	Prostate cancer treatment	Identification of participants	Quantitative descriptive	440/178/59	Various mass mailing, media, health service referral and community outreach strategies.	Mass mailing and health service referral strategies were moderately effective. Recruitment uptake was highest in participants identified through health service referral.	Fair
Kumar et al, 201243	Not specified	Prostate cancer prevention	Identification of participants	Quantitative descriptive	3547/167/74	Various media, health service referral and community outreach strategies.	Principal investigator referral was the only effective recruitment strategy. TV, newspaper, print and web-based communications and distribution of posters and flyers resulted in very few screenings.	Poor
Kusek et al, 200244	MTOPS	Benign prostatic hyperplasia treatment	Identification of participants	Quantitative descriptive	4170/NR/2931	Various mass mailing, media, health service referral and community outreach strategies.	Newspaper advertising and stories, and mass mailings were the most effective recruitment strategies.	Fair
Lee et al, 201145	CAMUS	Benign prostatic hyperplasia treatment	Identification of participants	Quantitative descriptive	1032/NR/369	Various mass mailing, media, health service referral and community outreach strategies.	Newspaper, radio and online advertising, and mass mailing were the most effective recruitment strategies. Emailing was less effective than traditional mailing.	Fair
Moinpour et al, 200046	PCPT	Prostate cancer prevention	Identification of participants	Before and after	NR/NR/18,822‡	Site-directed minority-targeted recruitment strategies conducted by funded minority recruiter site staff.	Minority-targeted recruitment strategies were not effective at four of the five sites awarded funds for a minority recruiter.	Poor
Donovan et al, 200235	PROTECT (feasibility)	Prostate cancer treatment	Participant information and consent	Before and after	NR/155/108	Site training and guidance documents to address recruitment issues identified through qualitative research.	Recruitment rates increased after introduction of the recruitment-focused site training and guidance.	Fair
Donovan et al, 200349	PROTECT (feasibility)	Prostate cancer treatment	Participant information and consent	RCT	NR/167/103	Recruitment visit conducted by nurse vs recruitment visit conducted by urologist.	Recruitment rates in the urologist and the nurse groups were not significantly different. Recruitment by nurse was more cost-effective than recruitment by urologist.	Good
Donovan et al, 200936	PROTECT	Prostate cancer treatment	Participant information and consent	Before and after	NR/2664/1643‡	Site training and guidance documents to address recruitment issues identified through qualitative research.	Recruitment rates fell slightly after introduction of the recruitment-focused site training and guidance.	Fair
Eccles et al, 201334	SABRE 1 (feasibility)	Prostate cancer treatment	Participant information and consent	RCT	286/30/4	30 min decision aid video providing trial information vs control (standard information).	Too few participants were recruited to assess effectiveness of the decision aid video. Some indication that the video may have decreased the recruitment rate when compared with control.	Fair
Wallace et al, 200650	SPIRIT	Prostate cancer treatment	Participant information and consent	Before and after	NR/290/32	Multidisciplinary group information session prior to recruitment vs one-on-one recruitment visit.	Recruitment rates increased after introduction of the multidisciplinary group information sessions.	Fair
Ford et al, 200451	PLCO/AAMEN project	Prostate, lung and colorectal cancer screening	Identification of participants, assessment of eligibility and patient information and consent	RCT	17 770/12 400/376	Three recruitment approaches of increasing intensity targeted at African-American men, compared with standard recruitment approach.	The most intensive approach to screening, which included face-to-face screening in a church setting, resulted in a higher recruitment rate than control. The improvement was statistically significant but small. Other less intense approaches were no better than control.	Fair
Lane et al, 201137	PROTECT	Prostate cancer treatment	Assessment of eligibility and participant information and consent	Before and after	NR/2664/1643‡	Peer-conducted site monitoring visits.	Recruitment issues were identified at two out of eight monitored sites. Specific recruitment metrics (consent form return rate, reduction in health-related exclusions) improved at these two sites following monitoring. The impact of the monitoring intervention on overall recruitment was not reported.	Poor

*Refers to number of participants screened (including prescreening), eligible (approached for consent) and randomised to the host RCT as part of the recruitment study.
†Quality rated as good, fair or poor with respect to the quantitative recruitment-related outcomes of interest in this systematic review.
‡Study did not report number of participants included in the recruitment evaluation. Instead total numbers of participants in host RCT are reported.
AAMEN, African-American Men; CAMUS, Complementary and Alternative Medicines Trial for Urological Symptoms; EASE, Eating, Activity , and Stress Education; MTOPS, Medical Therapy of Prostatic Symptom; NR, not reported; PLCO, Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial; PCPT, Prostate Cancer Prevention Trial; PROTECT, Prostate Testing for Cancer and Treatment; RCT, randomised controlled trial; SABRE, Surgery Against Brachytherapy—a Randomised Evaluation; SELECT, Selenium and Vitamin E Cancer Prevention Trial; SPIRIT, Surgical Prostatectomy versus Interstitial Radiation Intervention Trial; T, Testosterone TV, television.