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Correspondence  |   December 2015
Trials and Observations: A Friendly Pointer on the Language of Study Design
Author Notes
  • Mayo Clinic, Rochester, Minnesota. hyder.joseph@mayo.edu
  • (Accepted for publication August 20, 2015.)
    (Accepted for publication August 20, 2015.)×
  • This letter was sent to the author of the referenced article, who declined to reply.
    This letter was sent to the author of the referenced article, who declined to reply.×
Article Information
Correspondence
Correspondence   |   December 2015
Trials and Observations: A Friendly Pointer on the Language of Study Design
Anesthesiology 12 2015, Vol.123, 1481-1482. doi:10.1097/ALN.0000000000000900
Anesthesiology 12 2015, Vol.123, 1481-1482. doi:10.1097/ALN.0000000000000900
To the Editor:
I appreciate the fine efforts of Silbert et al.1  to improve our knowledge about patients at risk for postoperative cognitive dysfunction. However, the language used to describe their investigation would benefit from additional precision to improve interpretation and uptake of the study by the readership. Following are a few friendly clarifications.
The authors use the word “trial” to describe their study. It is not a trial. A trial is “a research activity that involves the administration of a test regimen to humans to evaluate its efficacy and safety.”2  Because there was no administration or assignment of exposure, this study was observational and not experimental. All trials, it should be noted, are prospective. Using the terms “prospective” and “trial” together, although increasingly common, is redundant to the point of risking confusion among readers.3 
Although the authors report that their trial was registered at the Australian Clinical Trials Registry, the study was described there as an observational study. Registration of observational studies at “clinical trials” registries such as ClinicalTrials.gov is an increasingly common, and good, scientific practice.
The authors use the words “prospective” and “observational” to describe their study. This is accurate, and the study should be interpreted as such.
The authors also refer to “patients” and “controls” in their study, terms that may lead some to assume it is a case-control study. This is not correct. In a case-control study, the cases and controls are selected based on the outcome. In this fine study, controls were selected based on the exposure. They may be referred to as groups with and without the exposure to surgery or surgical and nonsurgical patients. So why was the word “controls” selected? Perhaps the confusion about trials is to blame, because in trials, one group of patients is commonly referred to as a control group.
These details of language are critically important because language describes design, and design informs interpretation. Again, I congratulate the authors on this contribution to the literature and anticipate their future work.
Competing Interests
The author declares no competing interests.
Joseph A. Hyder, M.D., Ph.D., Mayo Clinic, Rochester, Minnesota. hyder.joseph@mayo.edu
References
Silbert, B, Evered, L, Scott, DA, McMahon, S, Choong, P, Ames, D, Maruff, P, Jamrozik, K Preexisting cognitive impairment is associated with postoperative cognitive dysfunction after hip joint replacement surgery.. Anesthesiology. (2015). 122 1224–34 [Article] [PubMed]
Porta, MS, Greenland, S, Hernán, M, dos Santos Silva, I, Last, JM, Burón, A A Dictionary of Epidemiology. (2008). Oxford Oxford University Press 289
Katan, MB The term prospective trial is a pleonasm.. Lancet. (2002). 360 806 [Article] [PubMed]