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Newell D J (Department of Medical Statistics, University of Newcastle upon Tyne, UK). Intention-to-treat analysis: implications for quantitative and qualitative research. 1992, 21: 837–841 Intention-to-treat analysis is an important aspect of randomized controlled trials of health care interventions. The concept is now widely accepted in theory, but not always implemented in practice. Failure to analyse by intention-to-treat can give misleading and indeed life-threatening interpretations. In some studies, a case is put for estimating the effect that would have been observed if all patients had received the allocated treatment. Situations where this is valid are rare, but an example is given of such an exceptional study. The relevance of the intention-to-treat concept is not always taken into account in qualitative research. Interviews with new mothers who delivered their babies at home in a hypothetical controlled trial of home versus hospital confinement would provide fascinating accounts of the pleasures of successful delivery at home. But by definition the interviews would exclude the hazard and drama of necessary transfers to hospital due to complications in late pregnancy and early labour. The intention-to-treat approach would avoid this bias. [ABSTRACT FROM PUBLISHER]

This paper reviews the implementation of a pragmatic multicentred randomized controlled trial in the evaluation of three experimental nursing homes. The organization of services for the care of elderly people varied between the three centres, and each used different criteria for selecting subjects for the trial and different methods of seeking informed consent. Data presented show that in each centre two truly randomized samples have been selected. However, differences between centres, in the characteristics of selected subjects, reflect the implementation of the trials in each of the centres. These findings emphasize the importance of good collaboration between health professionals providing the service, an independent research team, and the establishment of rigorous criteria for inclusion and exclusion of subjects at the outset. [ABSTRACT FROM AUTHOR]

This paper reviews the issues which arose in the design of a randomized controlled trial of three experimental National Health Service nursing homes. Problems associated with the implementation of the trial included ethical issues, choice of sample size and recruitment of subjects to the trial, choice and validity of measures of outcome, evaluation of outcomes and replicability of findings. The distinction between explanatory and pragmatic trials is shown to overcome some of these problems. [ABSTRACT FROM AUTHOR]