Osteoarthritis is the commonest rheumatic disease, but despite its high prevalence in the elderly, associated disability and public health costs, there is little understanding of the aetiology of the disease. Questions still remain unanswered: 'what do we mean by the term osteoarthritis?; how do we define it?; how do we classify patients with the disease?; how do we differentiate between cases for population studies, and clinically relevant disease the physician wishes to treat?'. This chapter has demonstrated the considerable advances that have been made over the last thirty years in solving these issues, but we are still lacking a universal definition and classification of the disease. Defining and classifying OA is not an easy task, as it is not a single disease, but rather a spectrum of diseases that are the end result of a number of different processes. However, in order to understand the aetiology and natural course of the disease, and to devise appropriate treatment strategies, correct definition of OA at distinct sites is vital. Radiological site-specific definition of the disease is now recognized as the major tool available in defining OA. There is general consensus that the grading of osteophytes and joint space narrowing at the major sites using validated atlases is an important step forward.

Diagnostic and classification criteria have the purpose of separating patients with a certain disease from those without the condition and from normal subjects. Specific identification of the different microcrystals establishes the definite diagnosis of crystal arthritides. The diagnostic criteria for gouty arthritis set up by the American Rheumatism Association in 1975 function well; both their sensitivity and specificity are satisfactory. Unfortunately, we have had no data on the real value of the diagnostic criteria used in CPPD or in hydroxyapatite deposition disease. Status or ranking criteria for stratifying patients by state of disease, such as activity or damage, have not been developed as yet in any type of crystal induced arthropathies. Reliable prognostic criteria sets and outcome criteria are clearly needed to indicate the course of the diseases at the onset, as well as to define the overall impact, of crystal deposition diseases.

The reliability and ease of use of any activity form has to be balanced against the content validity of the questions being asked. Clinical experience over several years suggests that presence of a high disease activity score is consistent both with the clinician's and patient's overall impression of disease activity. If the onset of the more serious manifestations can be predicted by more readily measured symptoms such as oral and genital ulceration, skin lesions, arthritis and superficial thrombophlebitis, then these organ system subscores could be expanded to provide a more accurate representation of activity. Other organ systems such as auditory system may also provide a measure of disease activity. For the purpose of clinical trials it is likely that if treatment is targeted at a specific organ system then a more comprehensive measure of activity within that organ system would have to be used (e.g. the role of thalidomide in oral ulceration) (Revuz et al, 1990). This would require the use of a form which measured many facets of oral ulceration (duration of ulcers, number of ulcers, size of ulcers, number of crops of ulcers, site of ulcers, etc). However it is recommended that such a form should be used in conjunction with a validated general disease activity form to alert the clinician conducting any trials of the advantageous or deleterious effects of the trial drug on other organ systems.

Classification of ankylosing spondylitis and spondylarthropathies is now satisfactory, but assessment of ankylosing spondylitis and related disorders could be improved. Currently, we do not completely encompass the spectrum of relevant outcomes. Functional status and toxicity assessment are frequently lacking. Although a considerable amount of progress has been made over the past decade in the development of patient status measures, this has mainly been achieved in rheumatic diseases that are characterized by predominant involvement of peripheral joints. This achievement is less prominent in ankylosing spondylitis. It may be relatively easy to define activity of extra-articular manifestations such as uveitis, but it is more difficult to define activity, severity, progress and outcome of a disease like ankylosing spondylitis with predominant spinal involvement.

The nomenclature and classification criteria for arthritis in children should be dealt with initially as separate issues, although they are undoubtedly intertwined. The classification criteria should aim to delineate homogeneous patient populations, yet should be flexible enough to incorporate advances in disease knowledge. It should be recognized that arriving at an international consensus for classification criteria will merely provide a set of operational definitions to facilitate research, and not a set of diagnostic criteria. Indeed the only point to obtaining consensus is to begin a process of systematic ongoing review of the criteria. The labels attached to any of these diseases should facilitate accurate communication. In view of the heterogeneous nature of childhood arthritis, consideration should be given to using a broad umbrella term such as juvenile or childhood arthritis only for communicating with the lay public. Medical nomenclature should be formulated to reflect accurately homogeneous subgroups of arthritis, and should not artificially proscribe a relationship between paediatric and adult disease.

Despite the fact that psoriatic arthritis has been recognized as an entity for almost five decades, there are still no valid criteria for either its diagnosis or classification. Several sets of criteria have been proposed but none was studied. None the less, investigators have been able to study the condition and describe its unique features and its natural course and prognosis. However, in order to facilitate further studies, it would be worthwhile to develop an internationally accepted and validated set of criteria, both for the diagnosis and classification of the disease, as well as for the assessment of damage. These criteria would help set up appropriate therapeutic trials in this condition as well.

Disease activity in rheumatoid arthritis is not easily measured. The validity of current measures has been reviewed. Recent international efforts have resulted in consensus over a minimum (WHO/ILAR) core set of endpoints in RA trials: pain, patient and physician (assessor) global assessment, physical disability, swollen joint count, tender joint count, acute phase reactants; and for studies of one or more years' duration: radiographs of joints. The near future will hopefully see validation of new measures, also in terrains not currently covered by the core set.

The development of classification schemes for RA in the last 40 years has followed the increasingly precise understanding of the nature of the clinical disease and the recognition of the different requirements of classification methods in clinic and population settings. In published studies of RA in clinic patients the most widely used criteria sets have been the 1958 ARA (ACR) criteria and its 1961 adaptation (the Rome (active) criteria). These sets classified disease as 'classical', 'definite', 'probable' and 'possible' RA based on criteria comprising clinical, serological, radiological and histological features (the latter were dropped from the Rome criteria set because of their impracticality). More recently, a new criteria set (the 1987 ARA criteria) has been developed using statistical techniques. This set was derived using RA cases and controls attending hospital clinics. It is based on the earlier criteria sets but accommodates the characteristic pattern of joint involvement in RA more precisely. The criteria recognize only the single disease category of 'rheumatoid arthritis'. In validation studies, the 1987 criteria set has been found to have enhanced specificity over earlier schemes in clinic-based studies of RA. The sensitivity may, however, be reduced, in particular in studies of early disease. The application of classification criteria for case recognition in the population and family studies of RA has proved more problematic. In these settings, there is the additional requirement to recognize individuals with remitted and inactive disease as RA cases. The 1966 New York criteria were developed for this specific purpose, however their format proved cumbersome and they have not been widely adopted. The 1987 criteria set is insufficiently sensitive to recognize inactive disease if the criteria are applied exactly as they have been defined. The sensitivity of the 1987 criteria set is, however, substantially enhanced if the criteria are adapted to incorporate features of past disease activity, for example by allowing deformity to substitute for swelling and by incorporating data on the past occurrence of rheumatoid factor and rheumatoid nodules. Developments in the immunology and genetics of RA may in the future provide more accurate tools for classification and may lead to recognition of more precise disease subsets. At present, however, the 1987 ARA criteria provide the most appropriate basis for case recognition in both clinic and population-based studies.

The methodology for developing and assessing disease status measures is now well-advanced. For some diseases, in particular SLE and RA, these methods have been applied and instruments either are being or have been validated. For other conditions, such as ankylosing spondylitis and Behçet's disease, there is still a need for reliable measures to be proposed and evaluated.

We have discussed methodological and statistical considerations in developing disease classification and assessment criteria. In choosing cases with disease and nondisease controls, classification criteria should be developed with an eye toward face, content and construct validity, and toward their ultimate applicability. The validity of disease criteria should be tested in a patient sample different from the one used to develop the criteria. Several analytic approaches are available to reduce the candidate diagnostic elements to those that will define the presence of disease. Methodological issues in the assessment of disease severity, activity or damage are similar to those faced in criteria development studies, although the analytic concerns are different and the options more varied.

There are few studies on the prevalence, pattern or clinical course of osteoarthritis (OA) in the tropics. The studies that have been carried out, however, indicate that on the whole there is a lower prevalence of OA than found in Western countries. In addition, the pattern of joint involvement may be different with less common involvement of the hip relative to the knee and polyarticular OA is uncommon in many parts of the tropics. It also seems likely that a significant number of these patients in the tropics have OA secondary to various infections including pyogenic, tuberculous and parasitic infections. There is an urgent need to confirm these observations and to identify possible genetic, developmental or environmental factors influencing the expression of OA in the tropics. In addition degenerative arthropathies, such as Mseleni's disease, present in some parts of the tropics, merit further study. With increasing life-expectancy and improved health-care in many parts of the tropics, OA will become an increasingly prevalent and important condition with associated morbidity and socio-economic implications for these countries.

With a few exceptions, there remains a paucity of good epidemiological studies from India and South-East Asia. The overall impression is that the prevalence of rheumatoid arthritis (RA) is slightly less compared with the West and follows a milder course. There may be differences in the articular expression of the disease with the wrist and forefoot less commonly affected than in Caucasian studies. Extra-articular manifestations and erosive change are less frequent and severe. HLA DR4 does not correlate with seropositivity and severity of RA. The prevalence of SLE may be less in the Indian subcontinent than in the West. However, recent indications are that in South-East Asia and the Pacific region the prevalence morbidity and mortality are higher than in developed countries. An improvement in socio-economic conditions may be accompanied by an improvement in the survival of patients with SLE.

Rheumatoid arthritis (RA) once a rarity in Africa, is now reported in large numbers from many parts of Africa. Although epidemiological surveys have shown that the prevalence in urban populations is similar to Western communities, it is less common in rural areas. Further epidemiological studies are needed to confirm these findings in other parts of Africa and identify factors contributing to this difference to provide a better understanding for the emergence of RA in Africa. Earlier reports suggested that in African blacks RA was a mild disease, severe radiographic changes were uncommon, deformities were rare and extra-articular features were unusual and only symptomatic therapy was necessary to control symptoms in most patients. Recent experience shows that severe disease with deformities and radiographic changes are seen and a wide spectrum of extra-articular features are noted although they may be less common than in Caucasians. African blacks with RA may have a younger age of onset and the genetic association with HLA DR4 has been confirmed. Systemic lupus erythematosus (SLE) is also recognized more often in African blacks who have a younger age of onset. SLE is also recognized less often in males. Features such as photosensitivity and serositis are less common while renal disease is more common. A reported short-term mortality of about 30% emphasizes the need for urgent efforts to improve the prognosis in SLE. The infrequent occurrence of localized systemic sclerosis and the absence of anti-centromere antibodies in blacks was noted in a recent large series of patients with systemic sclerosis. The other connective tissue diseases and systemic vasculitides are reported much less frequently and will probably be detected more often in future. Anti-cardiolipin antibodies are detected frequently in association with infections, including HIV infection. The spectrum of diseases associated with ANCA includes a variety of connective tissue diseases and infections such as HIV infection and invasive amoebiasis must be added.

There is still far too little information available on the rheumatic diseases in Africa. Epidemiological studies are required in order to determine the burden of illness from rheumatic diseases on the African continent as well as to identify local risk factors for certain diseases. Such studies will also serve to enable the development of preventative and rehabilitation strategies. Functional disability has to be assessed in relation to the prevailing sociocultural lifestyle on the continent. Measures of disability that reflect this await development whilst regional diagnostic criteria also need to be worked out. The validity of tests and the stability of test reagents in a tropical climate require analysis. Continuing assessment of rheumatological services is essential to ensure their effectiveness and efficiency in the community and in particular to determine health care priorities and the best forms of therapeutic intervention. This will enable judicious use of limited resources. Community surveys in Africa are fraught with constraints and are difficult to undertake owing to a shortage of manpower and financial resources. For this reason, most studies hitherto have been hospital based. Hospital studies though useful lack applicability to the population as a whole and consequently more emphasis on cross-sectional and longitudinal community studies are required. It is hoped that despite the restraints, these studies will be performed.

Six different mosquito-borne viruses (Chikungunya, O'nyong-nyong, Mayaro, Ross River, Sindbis and Barmah Forest) have been associated with arthritis in humans. These viruses are prevalent in the tropics and subtropics and they produce similar symptoms, consisting of fever, joint pains and rash. The symptoms are usually of short duration, around 1 week; complete recovery is the rule apart from exceptional cases of Chik infection. Precise diagnosis requires a serological service which is not available in many parts of the tropics these days. Treatment is symptomatic and there is no vaccine currently available. With an increasing number of visitors to the tropics being exposed to potential infection and with rapid air transport it is possible that visitors may return home during the viraemic incubation stage, infect the local mosquito populations and then develop clinical disease.

It has been recognized that the remarkable decline in infant mortality and the extension in human lifespan involving both developing and developed countries alike, has been influenced by social and economic developments and public health orientated measures (such as clean water and sewerage) rather more than by developments in medical research. However, the identification of important disease risk factors for a number of common conditions such as smoking, solar exposure, dietary fat and alcohol has led to further reductions in disease prevalence and mortality, at least in some countries. The varied success of strategies to reduce the mortality from circulatory, nutritional and diseases due to infection has had the predictable result of leaving communities more exposed to the chronic non-communicable diseases, especially those affecting the elderly. The COPCORD community-based studies, carried out largely in tropical Asia/Pacific countries, have indicated that the burden of musculoskeletal conditions as far as pain and disability, as well as from an economic point of view, are substantial and WHO has called for increased research and educational activities into the causes and consequences of chronic disease and in particular rheumatic diseases. To the problems of an increasing ageing population can be added the rapid growth of urban populations, new occupational stresses, lifestyle changes and a number of other factors (WHO, 1984). The common community-based rheumatic diseases are not RA or SLE that dominate admissions to hospital arthritis clinics. Pain and disability are most often caused by osteoarthritis, especially knee OA, and various soft tissue rheumatic problems producing neck, back, shoulder and elbow pain. Viral and reactive arthritis cannot be ignored and the complications from osteoporosis (although not normally considered a rheumatic condition), are a significant threat to ageing populations worldwide. It is clear that for many of these conditions, certain risk factors have been identified and that preventative strategies are becoming available although far more detailed research is still required (Wigley, 1993). Community education is an essential part of prevention and treatment and the ILAR-sponsored publication Aches and Pains--Living with Arthritis and Rheumatism (Hampton, 1992) is available in at least 10 different languages and fills an important need. Education helps to influence not only knowledge but also skills and attitudes.(ABSTRACT TRUNCATED AT 400 WORDS)

Over the past two decades in Latin America, there has been a slow but definite upsurge in studies on the epidemiology of RD but, thus far, the data on the distribution and determinants of RD in the population are limited, and knowledge of time trends and geographical differences in disease risk are lacking. It is still not clear what proportion of disabilities are due to RD. The impact of RD on communities in developing countries is believed to be substantial, due to the cost of treatment and rehabilitation, and loss of earnings. There are important gaps in our knowledge, leaving unanswered such questions as the cost of treatment and rehabilitation, and loss of earnings. There are important gaps in our knowledge, leaving unanswered such questions as the cost to society of RD and the potential impact of RD prevention on the overall burden of disability. It is also important to point out, however, that from the relatively simple descriptive studies which dominated the RD literature a few years ago, we are now witnessing a shift towards increasing sophistication in study design and incorporation of multicentre collaboration. The rheumatologists and epidemiologists in LA who have managed to continue their work merit admiration. Even with unavoidable omissions, this summary demonstrates that the epidemiology of RD is alive and well in LA, where it has managed to continue to function under extremely difficult conditions. Yet, few methodologists appear to have directed their attention to the unique challenges of conducting studies in a resource-poor environment.(ABSTRACT TRUNCATED AT 250 WORDS)

A firm theoretical basis for patient education in rheumatic disease care has been built up over the past 10 to 15 years. Education in self-management has enabled patients to control symptoms and become partners in care with their health providers. Education for fibromyalgia patients has come to the foreground during the last 5 years as health professionals have come to understand the syndrome better and recognize the role that stress plays in the exacerbation of symptoms. A few controlled trials of various strategies, such as aerobic conditioning and cognitive-behavioural techniques, have been reported recently. All have shown significant benefits to patients with fibromyalgia. Only one controlled trial has studied the effects of a self-management education programme alone. The results of this programme were positive. Self-efficacy and life quality were enhanced. This programme and an uncontrolled programme that integrated many strategies have shown some of the first positive long-term indications that patients who are treated intensively for even a short time can continue to improve as they practice self-management techniques. There is still a need for further documentation of non-drug treatment strategies and especially further research into who is helped by which strategies, the optimal length of time for a programme, and the need for ongoing treatment.

Many different interventions have been studied in the therapy of fibromyalgia syndrome (Tables 1 and 2). While most have been effective, in general these trials have been short term. Furthermore, important or substantial improvement, when it has been assessed, occurs in only small proportions of patients. Long-term, comparative trials of both efficacy and toxicity are necessary. Trials such as these require large numbers of patients (compared with placebo-controlled trials, which are generally impractical in long-duration trials due to the large numbers of dropouts in the placebo arm) and therefore are expensive and difficult to accomplish. Two other approaches offer potential solutions to the problem of adequate long-term comparative trials: (a) N-of-1 trials and (b) meta-analysis. N-of-1 trials have the advantage of random assignment, double-blinding and multiple potential comparisons in the same patient. Meta-analysis involves combining the results of studies, which individually may have conflicting results and lack adequate statistical power, to reach an overall result with sufficient statistical power to make meaningful conclusions, especially with respect to comparative efficacy. Peluso and colleagues (1993) have performed a recent meta-analysis of available therapies in fibromyalgia syndrome and found that the effect-size (a standardized measure of the efficacy of a given therapy) of several non-medication therapies such as electroacupuncture exceeded that of traditional medication therapies. Unfortunately, lack of uniformity in the use of outcome measures across included trials and the small numbers of comparable non-medication trials makes definitive conclusions regarding relative efficacy of therapies difficult. Nevertheless, application of meta-analytic methods such as these should facilitate future comparisons of different interventions. Ideally, future clinical trials in fibromyalgia syndrome should employ the same outcome measures to permit application of these methods. Few trials have assessed improvement in functional status. Functional status measures such as the HAQ (Fries et al., 1980), the Fibromyalgia Impact Questionnaire (Burckhardt et al, 1991) or similar instruments should be employed in future studies of therapy in fibromyalgia. Given that individual modalities appear to confer relatively modest benefit on average. Combination approaches are reasonable, although randomized, blinded trials to assess these approaches are methodologically complex. Several preliminary studies which have addressed this approach appear promising (see Chapter 12; Goldenberg et al, 1993). Finally, no studies have yet assessed the comparative cost-efficacy of available treatments. Controlled trials which address the cost-efficacy of commonly employed, but unproven treatments such as physiotherapy chiropractic manipulation and injection techniques are urgently needed.