title: Clinical trials: the challenge of recruitment and retention of participants.
abstract: OBJECTIVE
  This article, based on the available literature, attempts to discuss the importance of recruitment and retention of research participants, the associated barriers and challenges, and various strategies to overcome these barriers.
  
  
  BACKGROUND
  The inability to recruit and retain the required participants in a research project poses serious threats to both the internal and the external validity of a research study. Despite serious implications, the issues of recruitment and retention do not receive due attention in research and publications. Literature suggests a lack of coordinated efforts to collect information on the outcomes of recruitment experiences in clinical trials and population studies. Studies often mention the number of participants who refuse to participate; however, the majority of the studies often fail to mention the specific reasons insufficient recruitment or retention of the participants.
  
  
  METHODS
  A methodological paper.
  
  
  METHODS
  Various participant-, context-, environment- and research-related factors are examined that affect the phenomenon of recruitment and retention of the participants in a study.
  
  
  RESULTS
  Delayed or inefficient recruitment also has financial and ethical implications. Although there are many pieces of information scattered throughout academic journals on recruitment and retention of participants in research, few authors have dealt with the issue holistically. It is imperative for researchers to understand the importance of recruitment and retention of research participants, the associated barriers and challenges, and various strategies to overcome these barriers.
  
  
  CONCLUSIONS
  Appropriate recording and reporting of the problems faced while recruiting and retaining the participants in research studies can help not only in understating the challenge, but will also help in devising the strategies to overcome this problem. This article was an attempt to synthesise and review the available literature on recruitment and retention issues, which demand extensive theoretical and conceptual thinking as part of the research design.
  
  
  CONCLUSIONS
  An understanding of the challenges and issues related to recruitment and retention can help researchers to think ahead about the strategies to overcome these issues and consequently save the time and energy of the participants, researchers and funding agencies.
authors.affiliation: School of Nursing, Aga Khan University, Karachi, Pakistan. raisa.gul@aku.edu
authors.forename: Raisa B
authors.initials: RB
authors.lastname: Gul
authors.forename: Parveen A
authors.initials: PA
authors.lastname: Ali
mesh_terms: D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D008297:Male; D015399:Nursing Research; D010352:Patient Dropouts; D018579:Patient Selection