This paper presents a theoretical model to be used for comparative studies of lay and medically defined need for medical care. The model is based on an analysis of the concept of need and need statements, lay and medical concepts of ill health and the relationships between need, ill health and utilization of medical care. It is concluded, on both theoretical and empirical grounds, that need is relative to time, place and assessor. The most important determinants of assessments of for what and when one should seek medical attention are assumed to be the assessor's perception and valuation of the health status and his expectations of the probable out-come of medical care use. Assessment of need is seen as a process in which past experiences and expectations of the future course of the health status affect decision-making. It is emphasized that the points of view of both client and provider should be taken into consideration in medical practice, as well as in health care planning, because the two perspectives tend to be only partially congruent. The nature and extent of these incongruences could be studied by the application of the proposed model.

Utilization of care for rheumatic disorders was studied in two primary care units. In both units 12% of visits concerned some form of rheumatic disease. This diagnostic group (chapter XIII of ICD) ranked third after cardiovascular and respiratory diseases. The total number of visits per inhabitant was higher for all diagnoses, as well as for the rheumatic disorders, in the most remote primary care unit. The distribution of rheumatic diagnoses was similar in the two units. Back disorders were most frequent among men, whereas soft tissue rheumatism and back disorders each accounted for one-third of the cases among women. Inflammatory rheumatic diseases and osteo-arthritis played only a minor part. Visits due to rheumatic disorders decreased after retirement age, particularly among men. The findings were representative of primary care in rural areas of Sweden. Only 20% of referrals from primary care to the rheumatology department gave a tentative diagnosis and half of these suggestions were changed after examination. The majority of referred patients without any suggested diagnosis suffered from soft tissue rheumatism or inflammatory rheumatic disorders other than rheumatoid arthritis.

The validity and reliability of interview reports on rheumatic disorders in a Swedish nationwide health survey were studied. Two samples, including altogether 157 individuals, who had reported rheumatic disorders, were medically examined 6 to 24 months after the original interview. The reproducibility of the original interview was studied by the means of two re-interviews. The proportional distribution of rheumatic disorders according to diagnostic group was similar to that in the original interview, in the two re-interviews and at the medical examination. In a subject-to-subject comparison the overall agreement between the medical examination and the lay re-interview was 84% (kappa 0.35) regarding presence of rheumatic disorders, and 57% (kappa 0.41) regarding matching of rheumatic diagnostic groups. In the original interview and the lay re-interview the same individual rheumatic disorder was reported by 38% of the subjects; 58% agreed regarding rheumatic diagnostic groups. The interview reports on rheumatic disorders in the health survey can therefore be considered to have acceptable validity and reliability only with regard to the proportional distribution of groups of rheumatic disorders, based on aggregated data.

Utilization of care for rheumatic disorders (chapt XIII of ICD) was studied in an area of Sweden during 1978. In the total health care system, approximately 16 to 18% of the population with a rheumatic disorder were seen. The majority (12% of the population) of these patients were treated at the primary care centres. Only 1% were registered as in-patients, 1/4 of whom were admitted to the rheumatology department. Cases with back disorders constituted the largest diagnostic group of rheumatic disorders, both in primary care and in the departments of internal medicine, at the district level as well as in the regional hospital. The most important contribution of the rheumatology department was the care of a select group of patients--those with rheumatoid arthritis and systemic rheumatic diseases. However, primary care saw more patients also within the whole group of inflammatory rheumatic diseases. In the department of orthopaedic surgery, osteoarthritis was the major diagnosis among rheumatic disorders, totalling 38% of their rheumatic in-patients. Selection of patients for specialized care depended upon diagnosis, age, sex and distance to the hospital.

Utilization of rheumatological care by individual patients was studied in a Swedish county at all levels of the health care system. Calculated per population at risk, 0.6--0.8% per year were seen for rheumatoid arthritis. Of these, 35--81% were patients at the rheumatology department, varying according to distance of residence from the university hospital. The number of patients with other inflammatory diseases was, however, larger in primary care than in the specialist department. Only a minor part of the total care for rheumatic disorders (Chapt. XIII of ICD) in the county was provided by the rheumatology department. Back disorders constituted the largest diagnostic group of rheumatic disorders in primary care. During a period of one year a total of 12--14% of the population had contact with primary care, of the district hospital and/or the rheumatology department, because of rheumatic disorders. The results show the value of epidemiological studies to follow the development of and to define the future objectives of rheumatological care.