What do systematic reviews say?

Open trial vs blinded trial

Open trial leads to higher number recruited compared with blinded trial (high certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1.25 [1.18, 1.34]
  2 studies · 4833 participants
  High

Telephone reminder vs no telephone reminder

Telephone reminder leads to higher number recruited compared with no telephone reminder (high certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1.9 [1.35, 2.67]
  2 studies · 978 participants
  High

Brief participant information leaflet (PIL) vs usual PIL

Brief participant information leaflet (PIL) showed no clear difference in number recruited compared with usual PIL (moderate certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1 [0.93, 1.07]
  2 studies · 4633 participants
  Moderate

Participant information leaflet (PIL) developed with feedback from users vs usual PIL

Participant information leaflet (PIL) developed with feedback from… showed no clear difference in number recruited compared with usual PIL (moderate certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1.09 [0.96, 1.25]
  2 studies · 16763 participants
  Moderate

Providing information by video vs by standard means alone

It is very uncertain whether providing information by video changes number recruited compared with by standard means alone (very low certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1.08 [0.89, 1.31]
  3 studies · 4695 participants
  Very low

Financial incentive vs no incentives

Financial incentive showed no clear difference in number recruited compared with no incentive (moderate certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1.48 [0.85, 2.58]
  6 studies · 1506 participants
  Moderate

Bespoke, user‐tested participant information leaflet (PIL) vs usual PIL

Bespoke, user‐tested participant information leaflet (PIL) showed no clear difference in willingness to participate/number recruited compared with usual PIL (high certainty).

• Strategies to improve recruitment to randomised trials 2018 · Cochrane Headline outcomes only
  RR 1.15 [0.92, 1.44]
  3 studies · 6634 participants
  High

Monitoring with vs without initiation visit

• Monitoring strategies for clinical intervention studies 2021 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 573 participants
  Very low