Original Article
Survey among 78 studies showed that Lasagna's law holds in Dutch primary care research

https://doi.org/10.1016/j.jclinepi.2006.11.010Get rights and content

Abstract

Objective

Research in general practice has grown considerably over the past decades, but many projects face problems when recruiting patients. Lasagna's Law states that medical investigators overestimate the number of patients available for a research study. We aimed to assess factors related to success or failure of recruitment in general practice research.

Study Design and Setting

Survey among investigators involved in primary care research in The Netherlands. Face-to-face interviews were held with investigators of 78 projects, assessing study design and fieldwork characteristics as well as success of patient recruitment.

Results

Studies that focused on prevalent cases were more successful than studies that required incident cases. Studies in which the general practitioner (GP) had to be alert during consultations were less successful. When the GP or practice assistant was the first to inform the patient about the study, patient recruitment was less successful than when the patient received a letter by mail. There was a strong association among these three factors.

Conclusion

Lasagna's Law also holds in Dutch primary care research: many studies face recruitment problems. Awareness of study characteristics affecting participation of GPs and patients may help investigators to improve their study design.

Introduction

Research in primary care is essential to inform evidence based health care decisions of general practitioners (GPs) and allied workers [1]. Research activity in general practice has considerably increased over the past few decades [2].

Independent of setting, the recruitment of patients for a study often takes much more time than investigators have estimated. Many years ago, this phenomenon was coined “Lasagna's Law”, after the American clinical pharmacologist Louis Lasagna, who observed that when trial recruitment starts, the supply of suitable patients becomes a fraction of what it was assumed to be before the trial began [3].

Some articles have addressed this problem, but these were mostly case reports of single studies, which hampers generalization [4], [5], [6], [7], [8]. Foy et al. reported that very few recommended recruitment strategies for randomized trials in primary care are evidence based [9]. A systematic review of recruitment problems identified 78 randomized trials (1986–1996), only three of which were performed in general practice [10]. We performed a literature review and found only limited evidence for the impact of study characteristics and interventions on the success of patient recruitment. A Cochrane review concluded that it is difficult to generalize the effects of specific interventions from individual trials [11].

We aimed to assess factors that are related to success and failure of recruitment in general practice research, by systematically assessing potentially relevant factors in a large number of patient-related studies in Dutch general practice.

Section snippets

Projects

Through project leaders at the eight departments of general practice in the Netherlands; the Netherlands Institute for Health Services Research (NIVEL), and the Centre for Quality of Care Research, we made an inventory of all projects that fulfilled the following criteria:

  • Actual involvement of patients, either as subjects of an intervention study or as respondents to questionnaires;

  • General practice played an essential role in patient recruitment;

  • Patient recruitment completed between 1 January

Results

In the telephone inventory, 125 projects were identified as potentially eligible. Eighty-five of these were selected for an interview, and 78 of these interviews (92%) were completed. Reasons for not completing interviews were that these projects had erroneously been included, or that the person who could provide information was not available.

Discussion

This survey of 78 studies shows considerable variation in recruitment rates, at GP level as well as at patient level. Although a median of 87% of planned patients eventually being recruited may be interpreted positively, a considerable number of projects needed much more time than planned to obtain a sufficient number of patients. Almost 40% of projects had to extend the fieldwork period by at least 50%.

We studied several outcome measures as parameters of recruitment success. The study

Acknowledgments

Our thanks go to all our informants for their frank and elaborate information regarding the studies they were involved in, and to Valentien Blom for assistance in data entry.

ZonMW, the Netherlands Organization for Health Research and Development, project number 4200.0005, funded the study.

References (17)

  • S. Ross et al.

    Barriers to participation in randomised controlled trials: a systematic review

    J Clin Epidemiol

    (1999)
  • Mant D. R&D in primary care. National Working Group Report. UK: Department of Health, 1997. (Report No. 97CC0138.)...
  • I. Ovhed et al.

    What is the future of primary care? Probably fairly bright, if we may believe the historical development

    Scand J Prim Health Care

    (2005)
  • J.A.L. Gorringe

    Initial preparation for clinical trials

  • G. Tognoni et al.

    Randomised clinical trials in general practice: lessons from a failure

    BMJ

    (1991)
  • V. Peto et al.

    Factors affecting general practitioners' recruitment of patients into a prospective study

    Fam Pract

    (1993)
  • Tasche MJA. Practical aspects of a randomized controlled trial in general practice; patient recruitment, inclusion and...
  • D.A.W.M. Van der Windt et al.

    Practical aspects of conducting a randomised trial

    Br J Gen Pract

    (2000)
There are more references available in the full text version of this article.

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