Using quality of life measures in the clinical settingBMJ 2001; 322 doi: https://doi.org/10.1136/bmj.322.7297.1297 (Published 26 May 2001) Cite this as: BMJ 2001;322:1297
Validity: does the instrument measure what it is intended to measure, such as quality of life?
There are several questions to be considered when assessing the validity of measures for clinical practice.
· Does the measure cover factors that are clinically relevant to patients, their families, and health professionals—that is, does the measure have face validity?
· Are the domains appropriate, important, and sufficient for the setting or types of patients being studied—that is, does the measure have content validity?
· Does the measure correlate with a gold standard or superior measure—that is, does the measure have criterion validity? If there is no gold standard then an alternative question is to ask whether the measure produces results that conform to a theory. For example, a measure of weakness correlates with the stage of a patient’s disease (muscle strength, tone, and energy deteriorate as the severity of disease increases). This test, however, is only as good as the theory used.
Appropriateness and acceptability: is the measure suitable for its intended use? This property is crucial in clinical practice because measures must be simple to use.
There are several questions to be answered.
· Is the measure short enough or long enough to be completed or administered in the intended setting and with the types of patients, families, or informants for which it is intended?
· Are the format of the measure and the questions acceptable and suitable for use in the intended setting and with the intended informants?
· Has it been used in this or similar settings before, and did it work? If the measure is a translation, will it work in this culture and language? Has there been a double translation—that is, has it been translated into English and then translated back into the source language from the English version to ensure equivalence? Has its conceptual as well as its semantic equivalence been assessed?
Reliability: does the measure produce the same results when repeated in the same population?
Assessing reliability should include an assessment of the inter-rater (or inter-observer) reliability, which determines whether similar results are obtained by different observers, and test-retest reliability, which determines whether similar results are obtained at different points in time.
Another test sometimes used is whether individual items on the measure correlate with one other (known as internal consistency). This is not a true test of reliability. If a measure has very high internal consistency this suggests that many items in the measure are capturing the same factors, although it is likely that the measure is reliable. Thus, some items may be redundant and the measure could be shortened.
Responsiveness to change: does the measure detect clinically meaningful changes? This is sometimes called sensitivity.
Responsiveness is critical if the measure is to be useful in clinical practice. The questions that might be asked are whether the measure can discriminate between different degrees of severity or detect changes anticipated to occur given the proposed treatment. Patients who have progressive or advanced illness often score poorly on many quality of life measures (known as a floor effect), because the measures rely heavily on assessing the patient’s functioning as part of the assessment. Thus, changes in symptoms, family support, or other important components of care are not detected.
Interpretability: can results from the measure be interpreted clinically and are they relevant?
When given a quality of life score, or a series of scores over time, the clinician needs to be able to consider what to do with the information. For example, an overall quality of life score of, say, 5 out of 10 offers little information that will help in planning treatment. The clinician needs to understand what factors are affecting the patient’s quality of life—such as symptoms, concerns, or worries—so that appropriate treatment can be planned. To be clinically useful measures must provide easy access to the components of the assessment.
Potential use Possible application Training new staff in assessment The training of doctors and nurses has moved away from a purely knowledge based system to encompass training in skills. However, staff often overlook aspects of care, especially those relating to the quality of a patient's life. Quality of life measures that include information on factors important to the person (such as symptoms, functioning, and psychological and social wellbeing) can enable clinicians to gain an overview of an individual's problems. It can also help patients and clinicians to prioritise treatments, when there are several problems that need to be addressed. Training can include clinical assessment and interviewing skillsw1 along with the use of quality of life measures. Clinical audit Quality of life measures are an important part of the systematic assessment of the outcomes of care. Reviewing the goals of care and whether they have been achieved can help staff prepare to deal better with similar problems in the future. For example, this preparation may include training staff how to better manage a problem,w2 changing organisational aspects of care, or developing predictive profiles to help staff identify at an earlier stage those patients who may have problems.w3 Including quality of life measures in clinical audit ensures that the audit concentrates on what is important to patients, rather than just the technical aspects of quality. Clinical governance Quality of life measures can be incorporated into the framework of continual improvement and review which is being encouraged in the United Kingdom by the new guidance on clinical governance. Assessing the quality of life ensures that clinical governance focuses on what is important to patients and their families. Along with mortality and satisfaction, it is increasingly used as a criterion by which services and treatments are evaluated.
w1 Maguire P, Booth K, Elliot C, Jones B. Helping health care professionals involved in cancer care acquire key interviewing skills: the impact of workshops. Eur J Cancer 1996;32(suppl):1486-9A.
w2 Higginson I, McCarthy M. Measuring symptoms in terminal cancer: are pain and dyspnoea controlled? J R Soc Med 1989;82:264-7.
w3 Higginson I. Clinical audit in palliative care. Oxford: Radcliffe Medical Press, 1993.
- Is there such a thing as a life not worth living?BMJ June 16, 2001, 322 (7300) 1481-1483; DOI: https://doi.org/10.1136/bmj.322.7300.1481
- Who should measure quality of life?BMJ June 09, 2001, 322 (7299) 1417-1420; DOI: https://doi.org/10.1136/bmj.322.7299.1417
- Are quality of life measures patient centred?BMJ June 02, 2001, 322 (7298) 1357-1360; DOI: https://doi.org/10.1136/bmj.322.7298.1357
- Is quality of life determined by expectations or experience?BMJ May 19, 2001, 322 (7296) 1240-1243; DOI: https://doi.org/10.1136/bmj.322.7296.1240
- Measuring the impact of menopausal symptoms on quality of life.BMJ October 02, 1993, 307 (6908) 836-840; DOI: https://doi.org/10.1136/bmj.307.6908.836
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