What makes a good quality indicator set? A systematic review of criteria

BACKGROUND: While single indicators measure a specific aspect of quality (e.g. timely support during labour), users of these indicators, such as patients, providers and policy-makers, are typically interested in some broader construct (e.g. quality of maternity care) whose measurement requires a set of indicators. However, guidance on desirable properties of indicator sets is lacking. OBJECTIVE: Based on the premise that a set of valid indicators does not guarantee a valid set of indicators, the aim of this review is 2-fold: First, we introduce content validity as a desirable property of indicator sets and review the extent to which studies in the peer-reviewed health care quality literature address this criterion. Second, to obtain a complete inventory of criteria, we examine what additional criteria of quality indicator sets were used so far. METHODS: We searched the databases Web of Science, Medline, Cinahl and PsycInfo from inception to May 2021 and the reference lists of included studies. English- or German-language, peer-reviewed studies concerned with desirable characteristics of quality indicator sets were included. Applying qualitative content analysis, two authors independently coded the articles using a structured coding scheme and discussed conflicting codes until consensus was reached. RESULTS: Of 366 studies screened, 62 were included in the review. Eighty-five per cent (53/62) of studies addressed at least one of the component criteria of content validity (content coverage, proportional representation and contamination) and 15% (9/62) addressed all component criteria. Studies used various content domains to structure the targeted construct (e.g. quality dimensions, elements of the care pathway and policy priorities), providing a framework to assess content validity. The review revealed four additional substantive criteria for indicator sets: cost of measurement (21% [13/62] of the included studies), prioritization of ‘essential’ indicators (21% [13/62]), avoidance of redundancy (13% [8/62]) and size of the set (15% [9/62]). Additionally, four procedural criteria were identified: stakeholder involvement (69% [43/62]), using a conceptual framework (44% [27/62]), defining the purpose of measurement (26% [16/62]) and transparency of the development process (8% [5/62]). CONCLUSION: The concept of content validity and its component criteria help assessing whether conclusions based on a set of indicators are valid conclusions about the targeted construct. To develop a valid indicator set, careful definition of the targeted construct including its (sub-)domains is paramount. Developers of quality indicators should specify the purpose of measurement and consider trade-offs with other criteria for indicator sets whose application may reduce content validity (e.g. costs of measurement) in light thereof.