Pure Intervention Effect or Effect in Routine Health Care - Blinded or Non-blinded Randomized Controlled Trial

Background: Randomized trials provide the most valid evidence of effectiveness of interventions. The study aims to determine the primary study question for randomized controlled trials; to evaluate the study questions in trials on effectiveness of arthroscopic meniscectomy for meniscal rupture of the knee; and to explore the clinical and research implications.

Methods: Previous studies on benchmarking controlled trials were utilized. A literature search was undertaken to find the trials on arthroscopic surgery for meniscal rupture of the knee, data was extracted, and checked for accuracy twice.

Results: The first question in RCTs is whether to assess the pure intervention effect, or intervention effect in routine health care circumstances. The former necessitates a double blinded design and the latter a non-blind design. The trials on arthroscopic meniscectomy of the knee showed considerable differences in study characteristics.

Conclusions: The study question in RCTs on pure intervention effect dictates use of blinded design, while question of intervention effect in routine health care dictates use of non-blinded design. Blinding should not be considered a validity criterion when study question is on effectiveness in routine health care. When informing patients, the potential for other effects besides the pure intervention effect should be considered.