The prevalence of HLA-DR4 and HLA-DR3 in healthy persons with rheumatoid factor

Marker antibodies of rheumatoid arthritis: diagnostic and pathogenetic implications

Rheumatoid arthritis (RA) is associated with several autoantibodies specific enough to serve as diagnostic and prognostic markers. These include rheumatoid factor (RF), antikeratin antibody (AKA), antiperinuclear factor (APF), and anti-RA33. The first three, and possibly also anti-RA33, may precede the onset of clinical RA. The prevalence of positive test reactions depends on the period between taking the specimen and onset of disease; when the period is short, the prevalence is nearly the same as in established disease. Thus, RA has a long asymptomatic period with broadening immunological activity. The assays for AKA and APF (and possibly also for anti-RA33), compared with RF testing, yielded greater specificity rather than the ability to define any subgroup with particularly severe disease. Used together, the above marker antibodies may form a new and more enlightened basis for defining seropositive RA. It is commonly believed that genetically mediated immune response plays an important role in the initiation of RA. However, the role of the major histocompatibility complex antigens may be in modulation of the inflammatory reaction in a later phase.

Smoking, lung function, and rheumatoid factors

Positive rheumatoid factor (RF) reactions commonly precede the onset of clinically manifest rheumatoid arthritis (RA). Thus if items associated with RF reactions were traced at the community level this might provide clues to the cause of RA. The relations between smoking and lung functions and the occurrence of RA and RFs in a population sample representative of the adult Finnish population were studied. Rheumatoid factor testing was performed for 7124 subjects (89% of the sample) by the sensitised sheep cell agglutination test. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured with spirometry. 'False positive' RF reactions occurred twice as often in current smokers and ex-smokers than in those who had never smoked. The prevalence of high titres was fourfold greater among current smokers than among those who had never smoked. These associations were statistically significant and independent of age, FVC, and FEV1 in both sexes. The women with airflow limitation (FEV1/FVC less than 70%) had a significantly increased occurrence of RFs which was independent of their smoking history, but no such relationship was found in men. The results suggest an impact of smoking on RF production; a follow up study may show whether the raised RF titers in smokers will be reflected as an increased incidence of RA.

Rheumatoid factor tests in the diagnosis and prediction of rheumatoid arthritis

Four assays of rheumatoid factor (RF) have been measured on serum from 213 individuals from 13 families containing at least two sufferers from classical or definite rheumatoid arthritis (RA). Families were not uniformly RF positive or negative, and there was no evidence that non-RA RF positivity was inherited. Four individuals developed definite RA over a two year period, showing that the family members were at increased risk of RA. IgG RF and latex RF assays predicted the RA in the four cases. An association of RF positivity in RA with DR4 was observed, but this may be related to disease severity.