Not all measurement instruments are created equal

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Systematic reviews synthesize and summarize existing research and are considered to be the highest level of research evidence.1 Rigorous research design and use of validated measurement instruments are fundamental requirements for establishing strong evidence. Current efforts related to appraisal of evidence of effectiveness lean towards assessment of research design with seemingly little focus on the evaluation of the validity and reliability of measurement instruments used to gather the data. In fact, a significant number of relevant and well conducted systematic reviews reveal contradictory or inconclusive findings.2 While these reviews may make a contribution to the body of evidence, the lack of strong conclusions can limit the translation of quality evidence into practice and policy, with potentially negative consequences for health care consumers. This is in part due to the fact that studies that fulfil eligibility criteria and are included in systematic reviews often utilize different, incomparable or non-validated measurement instruments.
Developing a measurement instrument is an iterative endeavor that requires multiple rigorous methodological approaches and repeated testing (replication) and validation, often in diverse contexts and populations. In general, consideration must be given to the representativeness of measures (content validity), the appropriateness of constructs measured (construct validity), and the stability of measures (reliability).3 It is therefore important to critically evaluate the measurement properties of the available instruments by conducting a systematic review of their measurement properties. Systematic reviews of measurement properties aim to identify and critically evaluate the psychometric properties of existing instruments so as to derive a conclusion about the best instrument/s available for a particular purpose based on the available evidence.
The Joanna Briggs Institute (JBI) has an active and ongoing program of methodology and guidance development for the various types of JBI systematic reviews. Preparation and availability of standardized guidelines help to minimize bias and inconsistency, and establish validity of the findings. The JBI is currently developing appropriate resources and guidance to conduct systematic reviews of measurement properties. One of the goals of developing the standardized methodology is to provide guidance for reviewers on appropriate approaches to aggregate measures of psychometric properties. It is also anticipated that developing these guidelines will eliminate ambiguities by giving greater clarity to the formulation and interpretation of psychometric systematic review questions. The JBI will build upon expertise that has been established from two decades of conducting systematic reviews.
Despite the current lack of standardized methodological guidance for systematic reviews of measurement properties, several reviews4-6 and protocols7,8 have been published by the JBI, with others under development or consideration. By developing guidance for JBI systematic reviews of measurement properties, it is hoped the methodology will become more applicable to more reviewers. It is widely acknowledged that evidence based knowledge and methodologies are dynamic and will continually be enhanced by future findings. Therefore, the ongoing efforts by JBI are timely and must be commended, considering the significant international interest in conducting systematic reviews of measurement properties.
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