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Guidelines on Overweight and Obesity: Electronic Textbook
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1.e. Literature Abstraction and Preparation of Evidence Tables

In order to abstract the correct data related to the treatment portion of the model in a consistent manner, a 25-page form called the "Critical Review Status Sheet (CRSS)" was developed.  The CRSS was reviewed and approved by the panel. It took into account the inclusion and exclusion criteria described below and allowed for (1) the collection of data on the study's purpose and design; (2) the intervention parameters, including the format, setting, practitioners, population demographics, and detailed descriptions of the intervention per se, be it dietary, physical activity, behavioral, pharmacotherapy, or other types of interventions (surgery, acupuncture, hypnosis, etc.); and (3) outcome measures, including the method of determining the outcome, and adverse events. The CRSS was pilot-tested by staff as well as by staff of the San Antonio Cochrane Center.

The San Antonio Cochrane Center is one of 12 centers around the world that comprise the Cochrane Collaboration. The Cochrane Collaboration is an international organization established in 1993 whose mission is to prepare, maintain, and disseminate systematic reviews and meta-analysis of health care interventions.  The San Antonio Center provides advice on multiple aspects of systematic review, including searching and selecting materials, abstracting materials, organizing materials into evidence tables, and performing meta-analysis.

Inclusion and exclusion criteria. The appropriateness of an article was determined by applying criteria determined by the panel. These criteria included the time frame for the study, i.e., the minimum amount of time that must pass before the outcome measure is made; how body weight was reported; and the type and size of the study.  In defining the time frame, the panel needed to clarify whether the important outcome was weight loss or sustained weight loss. Due to the importance of both outcomes, the panel decided to include studies that considered the effects during the acute phase of weight loss, and those that examined effects during the maintenance phase. Both types of studies were deemed important, and two cutpoints were considered appropriate for follow-up. At a minimum, studies had to have a time frame from start to finish of at least 4 months. However, in order to consider the question of long-term maintenance, studies with outcome data provided at approximately 1 year or longer were examined. The panel decided to exclude studies that used only self-reported weights for their measurement. No exclusion of studies was made by study size.

Preparation of evidence tables. Of the 394 articles of randomized controlled trials considered for data abstraction by the San Antonio Cochrane Center, 158 were rejected for a variety of reasons; i.e., randomization was not adequate or subjects were not all overweight or obese.  Ultimately, 236 articles were abstracted by two separate reviewers who independently read and abstracted each article according to the CRSS.  The reviewers met, compared coding, and resolved discrepancies. The data were then compiled into individual evidence tables developed for each RCT. In addition, summary tables were developed to compile the evidence necessary to address the 23 questions relevant to the treatment portion of the model. All of the evidence tables are available for online retrieval.

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