To review the historical evolution of the Fatigue Impact Scale (FIS), presenting its main features and modified versions.

Two independent reviewers performed a search in PubMed for articles, available since the development of the scale until June 2012, looking for those studies that used the FIS or any of its modified versions as an instrument for data collection. The terms used for the search were “Fatigue Impact Scale.” After individual analysis and consensus procedure, 201 articles were selected for the data basis of this study. Data were extracted using standardized forms with the following information: version of the scale, year and country where the study was conducted, the methodological study's design, language in which the scale was applied, and how many patients responded to any one of the versions.

This review found 4 validated modified versions of FIS and 2 reduced forms, in 27 different countries. The largest concentration was in United States, followed by other English-speaking countries. The FIS was the version most commonly used, followed by the Modified Fatigue Impact Scale (MFIS). Approximately 46,483 individuals have been evaluated with one of the versions of FIS in 29 different pathologies. Most of these studies used a cross-sectional design.

The number of studies using the FIS and its modifications has grown substantially. However, this study evaluates methodological limitations which still hinder the synthesis of the scale's performance through meta-analysis. Still, the FIS has been used in relevant studies that contribute to understand fatigue broadly.