Searching methods for PROs are the same as for other outcomes (see Chapter 6). Usually all reports retrieved by the review’s search strategy will be examined to identify those that include the PROs of interest. Sometimes a separate, additional, PRO search might be used to supplement the standard strategy. For example, if a review of randomized trials and other studies in the area of asthma did not yield studies using PROs, a separate search could be performed to include search terms specific to PROs used in asthma, such as ‘asthma-specific quality of life’. However, this relies on there being mention of the PROs in the electronic record within the databases searched.
Index terms for PROs differ between the major bibliographic databases. Review authors cannot rely on a single index or subheading search term to identify studies addressing PROs. Multiple search terms are usually necessary. For example, Maciejewski et al. used the following MEDLINE index terms in their systematic review to estimate the effect of weight-loss interventions on health-related quality of life in randomized trials (Maciejewski 2005): 'Contingent valuation'; 'Health status'; 'Health-related Quality of Life'; 'Psychological aspects'; 'Psychosocial'; 'Quality of life'; 'Self-efficacy'; 'SF-36'; 'Utility'; 'Well-being'; 'Willingness to pay'. Free-text searches should also include as many relevant synonyms as possible. The search needs to combine index terms and free-text terms and is likely to take several iterations.
Review authors may find it useful to design and use a separate section of the data collection form used in the systematic review to include review of PRO methods and results. An example of such a form can be found on our web site: www.cochrane-pro-mg.org/documents.html. Review authors should attend to alternative ways of collecting data from instruments: in particular, whether they can collect data in forms that facilitate analysis of data both in the form of continuous variables and dichotomous outcomes.