Undifferentiated arthritis and spondylarthropathy as a challenge for prospective follow-up.

Diagnosis of arthritis with recent onset is still an unresolved problem. In 1984 we started an outpatient clinic for patients with early arthritis of less than one year duration. Of a total of 226 patients seen 149 (66%) had definite (n = 76; 34%) or probable (n = 73; 32%) inflammatory rheumatic disease, and 77 (34%) had degenerative or extraarticular rheumatic disease. Thirtynine patients were classified as undifferentiated arthritis. This undefined arthritis was often monoarticular (12%) and oligoarticuler (44%). One patient met 5 ARA-criteria for rheumatoid arthritis, 14 (36%) met 3-4 ARA-criteria and 25 (64%) only 1-2 ARA-criteria. ESR was elevated in only 23 (59%) patients, rheumatoid factor was positive in 7 (19%) patients and HLA-B27 was positive in 9 (23%) patients. Seventeen (44%) patients had a history of recent infections preceding the beginning of joint symptoms. Thus undifferentiated arthritis represents a heterogeneous group of diseases. Despite diagnostic progresses in recent years a high proportion of early arthritis cannot be diagnosed definitely.