Streamlining research with your choice of outcome measurement instrument

The need for establishing core outcome sets for use in clinical trials is becoming well defined though special attention should be given to the instruments used for measuring these outcomes. Here, Cecilia Prinsen and Lidwine Mokkink, members of the COSMIN Steering Committee, discuss the implications and importance of a new consensus based guideline for selecting outcome measurement instruments, which published today in Trials.

Standardization in outcome reporting is vital.

Clinical trials are used to investigate whether an intervention is effective and safe by evaluating the effects of the intervention on the (primary) outcome.

The instrument chosen to measure the outcome of interest is of utmost importance: conclusions are merely based on the scores of this instrument of choice. Scores should therefore be reliable, valid, and responsive to change over time so the conclusions of your clinical trial can be trusted.

It is known, however, that the quality of outcome measurement instruments used in clinical trials varies considerably. Moreover, it is usually not apparent if the most reliable and valid outcome measurement instrument has been selected to measure the outcome of interest.

… the quality of outcome measurement instruments used in clinical trials varies considerably…

It therefore surprises us that, when judging the methodological quality of clinical trial studies in systematic reviews, very little or even no attention is being given to the quality of the outcome measurement instruments that were used in the included trials.

What if the selected outcome measurement instrument is of poor quality? Not surprisingly, scores obtained cannot be interpreted nor be trusted. Consequently, wrong conclusions can be drawn.

The importance of uniformity in outcome reporting

Using inadequate outcome measurement instruments is both unethical and a waste of research. Outcome measurement instruments should therefore be carefully selected. It should be the best outcome measurement instrument available at present, as we need to make sure that we can rely on the results that are based on these measurements.

Using inadequate outcome measurement instruments is both unethical and a waste of research.

Alongside the selection of the best outcome measurement instrument available, there is another important aspect that we would like to highlight.

Multiple trials will often be used to answer a single research question. Our best evidence is found in a systematic review and meta-analysis in which the results of multiple clinical trials are compared and pooled, if possible.

We know that different outcome measurement instruments are continuously being used to measure the same outcome across clinical trials for a specific health area.

In a recent systematic review, written on behalf of the HOME (Harmonising Outcome Measures for Eczema) initiative, we identified 17 different outcome measurement instruments to measure health-related quality-of-life in adult patients with atopic eczema.

This lack of standardization in outcome measurement and reporting, makes it very difficult, or even impossible, to compare and pool results across clinical trials in systematic reviews and meta-analyses. It is a serious threat to comparative effectiveness research as it hampers the usefulness of clinical trial evidence to inform healthcare decisions.

And, it has also been shown that these unstandardized outcomes are not always the outcomes that patients say matter to them.

Towards standardization

A solution to the issues highlighted above is standardization in outcome reporting by means of developing and using Core Outcome Sets (COS).

A COS is an agreed minimum set of outcomes that should be measured and reported in all clinical trials of a specific disease or trial population. It is a recommendation of what should be measured and reported in all clinical trials, and how the core outcomes should be measured, i.e. which outcome measurement instruments should be used.

The COMET (Core Outcome Measures in Effectiveness Trials) initiative brings together people interested in the development, reporting and application of COS.
The COMET (Core Outcome Measures in Effectiveness Trials) initiative brings together people interested in the development, reporting and application of COS.

Outcomes in a COS are consensus-based, involving patients, healthcare providers and other key stakeholders; they are outcomes that matter to the patient.

But, it is not only the choice for outcomes that matters, it is also the choice of outcome measurement instruments to measure these core outcomes. The outcome measurement instruments that are included in the COS are the best instruments available at present, based on thorough systematic reviews of outcome measurement instruments.

New guidelines for selecting your outcome measurement instrument

Published today in Trials, we present a consensus-based guideline that describes the methods for selecting outcome measurement instruments for outcomes included in a COS and clinical trials for any disease or condition in health and social care.

… we present a consensus-based guideline that describes the methods for selecting outcome measurement instruments for outcomes included in a COS and clinical trials…

Using COS does, by no means, imply that researchers are restricted to these outcomes. In fact, the outcome(s) of interest of a specific clinical trial may differ from the outcomes included in the COS. Rather, reporting the core outcomes as a minimum in all clinical trials for a specific health area makes it possible to compare and combine results in systematic reviews and meta-analyses; it is key in comparative effectiveness research and evidence-based medicine.

To bring a medical field forward, without wasting resources, standardization in outcome reporting is considered vital.


cosminAre you interested in reading more about selecting outcome measurement instruments? The COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) Group is continuously working on improving the selection of outcome measurement instruments both in research and in clinical practice by developing tools for selecting the most appropriate instrument, see http://www.cosmin.nl/.

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