Assessment of disease activity

doi:10.1016/S1521-6942(03)00026-3

Best Practice & Research Clinical Rheumatology

Volume 17, Issue 3, June 2003, Pages 415-426

https://doi.org/10.1016/S1521-6942(03)00026-3 Get rights and content

Abstract

The concept of disease activity is useful for characterizing chronic rheumatic diseases and their current degree of severity. Disease activity should be clearly differentiated from damage, which is irreversible. A number of requirements must be met in order to make a measure of disease activity acceptable and valid. Methods for measurement have been developed in the areas of biological, radiographic, ultrasound and computerized imaging techniques. Recently, a particular effort has been made to develop questionnaires in the form of complex indices, derived from the observations of physicians, and self-report questionnaires for patients. Such assessments of disease activity are available for most of the chronic inflammatory rheumatic diseases. They are particularly relevant at a time when new biological drug therapy is being developed. Research effort is needed to develop more instruments suitable for use in clinical practice for individual patients.

Section snippets

The concept of disease activity

The concept of disease activity is a common and practical approach to the understanding of chronic rheumatic diseases in clinical practice. It characterizes an underlying process, implying progression of the disease. It is usually accepted that a pathological process, whether from inflammation, infection or ongoing injury, will damage tissues and become clinically perceptible with the deterioration of any organs affected or triggered by the disease.

Inflammatory arthritis is the main category of

The purpose of assessing disease activity

Characterization of the process of disease activity has several consequences in terms of patient care. It is hoped that by prescribing treatment which can slow (or even halt) this process, a lower level of damage will occur over time in chronic diseases. Disease activity is also an area of interest for research. An understanding of the underlying mechanisms of disease activity is necessary for an understanding of the origin of disease; these mechanisms have recently been the target of new drug

Measurement: methods and properties

Methods of measurement should have well-defined properties to ensure that they are useful in practice. Clinicians generally require that an assessment be sensitive, i.e. able to label a patient as suffering active disease when there is, in fact, an active disease process. They also require an assessment to be specific, i.e. able to label a patient as inactive when their disease in not in an active phase. Sensitivity and specificity would be easy to check if there were a gold standard for

Types of measurement

Disease activity can be monitored using a variety of measures in different domains. Originally identified as a biological phenomenon, disease activity is easily identified in clinical practice by imaging techniques or by endoscopic technology.

Disease activity can be measured by single or aggregate measures. Single measures in clinical practice are biological or clinical symptoms. Biological markers commonly used are the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), a

Rheumatoid arthritis

Among single measurements, joint counts can be assessed by the physician, by nurses or by the patients themselves. A study ascertaining the validity of joint count performed by patients found that the degree of agreement was sufficient to allow it to be used for clinical research¹⁸, but not directly interchangeable with physician's count and yet questionable to guide clinical practice.¹⁹

Recently, activity measures have been included in the standard American College of Rheumatology (ACR)

Conclusion

In practice, the assessment of disease activity serves many purposes which benefit the patient in terms of diagnosis, prognosis and treatment decision. Several instruments are available, and indices combining different types of clinical information are considered relevant to such assessment. However, these measures have limitations in the categories of disease covered and in their validity for use in monitoring individuals accurately. Research is still needed to incorporate the patient's

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