The 2 “Es” of Research: Efficacy and Effectiveness Trials

Abstract

Studies that investigate the usefulness of various therapies fall along a continuum that ranges from those looking at whether an intervention can work under ideal circumstances (efficacy trials) to those that focus on whether a treatment works when applied in the real world (effectiveness trials). Whether a study is closer to one end of the spectrum or the other affects almost every aspect of the trial. These aspects include which patients are eligible for enrolment, the degree of control over the way the intervention is delivered, which patients are or are not included in the analyses, how missing data are handled, and even which statistical tests may be used. The 2 types of trials may yield different results, but both provide useful information. This paper explores these issues, shows the decisions researchers must take at each phase of a trial, and discusses how clinicians should interpret the results.

Tension‐free vaginal tape: Do patients who fail to follow‐up have the same results as those who do?

“…It has been shown that when the surgical outcome among all patients initially included in a trial is analyzed as opposed to those who are only available for follow-up, the results may lose their signi¢cance [Sackett and Gent, 1979]. The treatment may seem e¡ective when patients with only good follow-up visits are included; however, its generalizabil- ity to the other populations may not be applicable [Grady et al, 2001;Streiner, 2002].…”

“…In surgical intervention trials, patients who are lost to follow-up may not have as good a success rate or as favorable a complication rate as those who have good follow-up, due to dissatisfaction with the results. Although the intervention may appear e⁄cacious when only those who come back for the follow-up visits are included, its internal validity may be lost [Streiner, 2002].…”

Subsyndromal Mood Symptoms: A Useful Concept for Maintenance Studies of Bipolar Disorder?

“…As proposed for nonpsychiatric illnesses with unclear pathophysiology, some maintenance agents may only influence a portion of a complex disease process or may act through an unintended, independent mechanism of action [57,58] . Lastly, the issues relating to efficacy studies and the apparent overestimation of the effectiveness of medications in clinical practice have been well documented [59,60] .…”

Effectiveness of Guided Internet-Based Cognitive Behavior Therapy in Regular Clinical Settings

“…However, there is no sharp distinction here, and it can be argued that clinical intervention research, e.g., trials on psychotherapy, always have elements of effectiveness as they include real patients with disorders that are indeed both comorbid and severe [Stirman et al, 2003]. Moreover, efficacy and effectiveness studies can be regarded as extremes on a continuum [Streiner, 2002]. For example, a study may be conducted in a specialist research clinic, but with regular patients referred to the treatment, and the therapists who provide the treatment may be both clinicians and researchers.…”