The intrafamilial transmission of rheumatoid arthritis. II. An interview measure of rheumatoid arthritis.

RHEUMATOID arthritis is a remittent disease, and in its milder forms the people involved spend more time free of the disease than they do with the disease [l, 21. This means that at a single clinical examination those with mild disease are unlikely to be identified because there is a high probability that they will be free of disease at any given point in time. More specifically, those who spend on the average only 10 weeks per year with joint swelling will have only 1 chance in 5 of being classified as having rheumatoid arthritis at a single examination because the diagnostic criteria of the American Rheumatism Association [3] require that the swelling be observed by the physician. Thus, population studies using a single clinical examination identify a group of rheumatoid arthritics that is overloaded with persons who spend a large proportion of their time in an episode of active disease and that is underloaded with persons who spend only a small proportion of their time in episode. When one is trying to characterize persons with the disease in regard to some set of variables, it is important that one include the full range of severity and not confine one’s study simply to severe and continuously affected cases.