Pure intervention effect or effect in routine health care - blinded or non-blinded randomized controlled trial

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.

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.

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.

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.