Background: Evidence on recruitment strategies for Veterans Health Administration (VA) pragmatic clinical trials (PCTs) is scarce. This study compares multiple approaches and evaluates engagement, efficiency, and representativeness in the integrated care setting of VA.
Methods: We examined recruitment and screening processes used in the Veterans Response to Dosage in Chiropractic Therapy (VERDICT) PCT. Veterans with chronic low back pain were recruited and enrolled in 4 US VA facilities from February 2021 to May 2024. We used 3 recruitment strategies: existing referrals for chiropractic services, electronic health record (EHR) prescreen, and self-referral. Pre-enrollment contacts occurred through postal mail, email, and in-person or virtual baseline visits. We used 5 sequential screening steps leading to final eligibility determination: (1) identify and notify, (2) phone screen, (3) consent, (4) eligibility questions, and (5) chiropractic consultation.
Results: We screened 3667 veterans: 91% were identified through existing referrals, 7% through EHR prescreen, and 2% through self-referral; 62% received postal-only recruitment materials, 38% received a combination of postal + email materials, and 83% had a virtual baseline visit. Over 39 months, 766 individuals were enrolled and randomized. Due to limited VA chiropractic clinic capacity, 19% of eligible veterans were not enrolled. Across all steps of the screening process, 45% were not interested, and 35% were ineligible. Using existing referrals was the most efficient strategy, with a median time from notification to randomization of 23 days. Those emailed invitations had a median response time of 16 days, compared with 30 days for postal-only invitations. The existing referrals strategy was the most effective for recruiting racial and ethnic minorities (33%). EHR prescreen resulted in the highest proportion of female veterans (79%).
Conclusions: This study is among the few to compare multiple recruitment strategies in a VA PCT while assessing engagement, efficiency, and representativeness. VERDICT shows that PCTs can overcome recruitment challenges through adaptable, multifaceted approaches. By addressing systemic barriers and implementing email and virtual strategies, we improved recruitment engagement and diversity. These methods can inform recruitment for trials in other VA-based and real-world settings.
Trial registration: Clinical trial registration number: NCT04087291. Participant enrollment began on February 22, 2021, and ended on May 10, 2024. Registered on August 27, 2019.
Keywords: Chiropractic; Chronic pain; Electronic mail; Low back pain; Patient selection; Pragmatic clinical trial; Veterans.
© 2026. The Author(s).