Original Article
Telephone reminders are effective in recruiting nonresponding patients to randomized controlled trials

https://doi.org/10.1016/j.jclinepi.2003.12.015Get rights and content

Abstract

Objective

Studies investigating means of recruiting participants to randomized controlled trials (RCTs) are sparse. We investigated the effects of telephone reminders as a recruitment strategy.

Study Design and Setting

Sick-listed employees received a written invitation to participate in a study comparing standard treatments with a solution-focused follow-up and were randomly allocated to an intervention or control group (n = 703). Those who did not respond within 2 weeks received either ‘no reminder’ (n = 242) or ‘attempted telephone reminder’ (n = 256). Outcome was enrollment to the RCT.

Results

An intention to recruit analysis revealed no significant differences between the groups (P = .229). An intention to phone analysis among nonresponders revealed significant differences between ‘no reminder’ (recruited 4.5%) and ‘attempted telephone reminder’ (recruited 12.1%) (P = .003, odds ratio 2.89, 95% confidence interval [CI] 1.42–5.90). An analysis of numbers needed to phone showed that to recruit one more person in this group of nonresponders, we needed to phone 13 persons (95% CI = 8–33).

Conclusion

Systematic use of telephone calls can increase the recruitment rate among nonresponders in RCTs.

Section snippets

Background

Recruiting participants to a randomized controlled trial (RCT) is often a demanding task. Important barriers to participation have been identified as added demands when participating, possible damage to the professional relationship, and concerns about the procedures of recruitment and consent [1]. The validity of any study rests on how representative the sample is, as any inference drawn applies only to the sample taking part in the study. An increase in uptake rate is expected to increase the

Design

The study design was a randomized controlled trial of a structured telephone follow-up versus no telephone follow-up to a recruitment letter into a community based trial.

Participants

Employees (age 16–66) sick-listed for more than 7 weeks due to nonsevere psychological problems or musculoskeletal pain were eligible (Table 1). Diagnosis was made according to the International Classification of Primary Care (ICPC). The ICPC has been used by Norwegian physicians since 1992 and has been shown to have acceptable

Results

A total of 703 persons received a letter informing them about the project. Among the recipients, 301 persons (42.8%) had musculoskeletal disorders, 323 (45.9%) had mental health problems, and 79 (11.2%) had various other diagnoses. Nearly half the sample (347) had only one episode of sick leave in the last 2 years; the others had two or more episodes in the last two years. Average age was 41.3 years. Characteristics of all participants are shown in Table 1.

Small differences were found between

Discussion

By phoning eligible persons who had not responded to a written invitation, we increased the number of additional subjects recruited to the RCT.

The strength of this study is that it was a randomized comparison with 100% follow-up for the main outcome, the number of persons recruited to an RCT. This illustrates the power of a well-designed RCT, with internal validity as high as possible; however, we believe that the results should be discussed regarding external validity.

The obvious solution to

Conclusions

The intention to recruit analysis revealed nonsignificant results.

Uptake among nonresponders was significantly increased by a simple telephone reminder, which suggests that such a reminder should be used whenever possible. Systematic use of telephone contact might be a very effective way to increase the uptake rate in RCTs. Recruiting a larger percentage of the population to the study sample might also add to the external validity of study results.

Acknowledgements

The authors thank the Royal Ministry of Social Affairs, Norway, for funding this study. This study could not have been done without the support and contributions of the representatives of the local social security offices. The project team and especially the phone follow-up coordinator, Hildegunn Waal, should be credited for their enthusiastic energy and empathetic approach.

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