چک لیست COSMIN برای ارزیابی کیفیت روش شناختی مطالعات در زمینه ویژگی های اندازه گیری ابزارهای اندازه گیری وضعیت سلامت: یک مطالعه بین المللی دلفی The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: an international Delphi study

Introduction Measurement of health outcomes is essential in scientific research and in clinical practice. Based on the scores obtained with measurement instruments, decisions are made about the application of subsequent diagnostic tests and treatments. Health status measurement instruments should therefore be reliable and valid. Otherwise there is a serious risk of imprecise or biased results that might lead to wrong conclusions. Organisations such as the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) require that measurement instruments must be well validated for its purpose [1, 2]. The need for reliable and valid measurement instruments of health outcomes was clearly demonstrated by Marshall, who showed in schizophrenia trials that authors were more likely to report that treatment was superior to control when an unpublished measurement instrument was used in the comparison, rather than a published instrument [3]. Before a health status measurement instrument can be used in research or clinical practice, its measurement properties, i.e. reliability, validity and responsiveness, should be assessed and considered adequate. Studies evaluating measurement properties should be of high methodological quality to guarantee appropriate conclusions about the measurement properties of an instrument. To evaluate the methodological quality of a study on measurement properties, standards are needed. Although many standards and criteria have been proposed, these have not been operationalised into user-friendly and easily applicable checklists (e.g. [4, 5]). Moreover, these standards do not pay attention to studies that apply Item Response Theory (IRT) models, or are not consensus based (e.g. [6, 7]). Such a checklist should contain a complete set of standards (which refers to the design requirements and preferred statistical methods) and criteria of adequacy for what constitutes good measurement properties. Broad consensus is necessary in order to achieve wide acceptance of a checklist. Research on measurement properties is particularly important for health outcomes that are directly reported by patients, i.e. health-related patient-reported outcomes (HR-PROs). A HR-PRO is a measurement of any aspect of a patient’s health status that is directly assessed by the patient, i.e. without the interpretation of the patient’s responses by a physician or anyone else [2]. Modes of datacollection for HR-PRO instruments include intervieweradministered instruments, self-administered instruments, or computer-administered instrument [2]. Examples of HR-PROs are questionnaires assessing symptoms, functional status, and health-related quality of life. These are constructs which are not directly measurable. Because of the subjective nature of these constructs, it is very important to evaluate whether the measurement instruments measure these constructs in a valid and reliable way. The COSMIN initiative (COnsensus-based Standards for the selection of health Measurement Instruments) aims to improve the selection of health measurement instruments. As part of this initiative, the aim of this study was to develop a checklist containing standards for evaluating the methodological quality of studies on measurement properties. The checklist was developed as a multidisciplinary, international collaboration with all relevant expertise involved. We performed a Delphi study to address two research questions: 1. Which measurement properties should be included in the checklist? 2. How should these measurement properties be evaluated in terms of study design and statistical analysis (i.e. standards)? In this paper, we present the COSMIN checklist, and describe the agreement of the panel concerning the items included in the checklist. Methods Focus of the COSMIN checklist The COSMIN checklist is focused on evaluating the methodological quality of studies on measurement properties of HR-PROs. We choose to focus on HR-PROs, because of the complexity of these instruments. These instruments measure constructs that are both multidimensional and not directly measurable. In addition, we focused on evaluative applications of HR-PRO instruments, i.e. longitudinal applications assessing treatment effects or changes in health over time. The specification of evaluative is necessary, because the requirements for measurement properties vary with the application of the instrument [8]. For example, instruments used for evaluation need to be responsive, while instruments used for discrimination do not. The COSMIN Steering Committee (Appendix 1) searched the literature to determine how measurement properties are generally evaluated. Two searches were performed: (1) a systematic literature search was performed to identify all existing systematic reviews on measurement properties of health status measurement instruments [9]. From these reviews, information was extracted on which measurement properties were evaluated, and on standards that were used to evaluate the measurement properties of the included studies. For each measurement property, we found several different standards, some of which were contradictory [9]. (2) The steering committee also performed another systematic literature search (available on request from the authors) to identify methodological articles and textbooks containing standards for the evaluation of measurement properties of health status measurement instruments. Articles were selected if the purpose of the article was to present a checklist or standards for measurement properties. Standards identified in the aforementioned literature were used as input in the Delphi rounds.