Rheumatoid arthritis (RA) is a chronic disease with severity and consequences varying from one patient to another, and potential impact on individual, family and society over the long term.
The impact can be defined as the various outcomes beyond the patho-physiological disease process. The components of the impact of RA comprise of joint damage, functional disability, impairment of quality of life in several dimensions and socio-economic consequences, like work disability, social participation restriction, and economic costs. These consequences should be analysed in the frame of the recent revision of the international classification of impairment, disability and handicap (ICIDH-2). This model will help understand the mechanisms of resistance to and limitation of the impact of the disease.
The measurement of such outcomes has largely benefited of research focused on this particular disease in the past two decades. A reliable measure is necessary to assess the impact, and to document the progression of impact over time. Outcome measures should be sensitive to natural changes or therapy effects over the disease progression.
- Radiographic lesions are now well documented by increasingly accurate and standardised assessment scoring methods of joint damage.
- Self-assessment questionnaire of functional disability has now its standard, the HAQ, with some variants, primarily developed and documented in RA.
- Health-related quality of life measures have been an exploding area of methodology and research development in the recent years, making generic and RA specific instruments like the AIMS2, or the AIMS2 Short Form valid and easily accessible in clinical practice.
- Socio-economic consequences are less documented. Several studies have examined and quantified the amount of work disability the frequency of which varies by country. Recent analysis of the EURIDISS cohort study has examined the social network changes and the influence of social support provided to patients. The direct and indirect costs of RA have been well documented in some country and appear substantial.
The prediction of outcome by a simple equation modelling outcome as a function of measurable predictors would be ideal for monitoring patient therapy from the very start of the disease. Unfortunately, despite extensive studies looking at large numbers of patients, a part of individual variation and the irregular progression over time still challenges the search for an accurate group of predictors. It is readily possible to obtain a reasonable probability estimate of outcomes from a consensual set of determinants that will be reviewed. But it is not yet possible to monitor individual patient with sufficient accuracy, with the exception of a few outcomes using mathematical models demanding intensive data collection.
In an epidemiological perspective, longitudinal observational studies are the standard to determine such predictors. They can be conducted retrospectively, with the risk of selection and measurement bias, or prospectively, at the cost of study duration and loss to follow-up. The identified determinants of radiographic damage and of functional disability will be reviewed, while the prognostic factors of quality of life have been less frequently documented over time. Determinants of health care resources utilisation and of cost of illness are being investigated.
A better knowledge of predictors of RA impact, if modifiable by a medical or a social intervention, helps decrease the severity of the condition, decrease the frequency of deleterious consequences, increase patients quality of life and reduce costs to society. An investigation of societal and economic aspects of the disease impact is still needed over the long term. Condition for impact prediction may well change with the RA condition recently entering a new therapeutic era.
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