Early arthritides: nosography, nosology, and diagnostic criteria.

Follow-up studies of patients with early arthritides are sparse and they are usually restricted to certain diagnostic groups. Therefore 141 unselected patients suffering from arthritis since no more than 12 months were entered into a prospective study. The largest group (n = 57, 40%) consisted of patients with definite rheumatoid arthritis. Forty individuals (28%) were judged to have undifferentiated arthritis since they could not be classified according to established diagnostic criteria initially. After 9 +/- 3 months mean follow-up only 21 of 45 patients (47%) fulfilling criteria for definite rheumatoid arthritis at the onset of the study remained in this category, 9 (20%) still suffered from arthritis but they met less than 5 ARA criteria, and 15 (33%) went into remission. Among 50 patients with undifferentiated arthritis or spondylarthropathy an even smaller proportion of 16 individuals (32%) still had arthritis, which could not be classified, whereas 34 (68%) showed no signs of persisting peripheral arthritis. Thus, criteria diagnoses are inadequate for the selection of the patients at the onset of the disease since they are frequently false positive and they omit other arthritides important for differentiation. Further disadvantages of criteria diagnoses are evident: they imply a large spectrum of manifestations of the disease, they overlap with other entities, they do not provide sufficient information regarding the prognosis and adequate treatment. To improve the prognostic value of a nosological classification a concept of descriptive diagnoses is discussed.