Silica exposure is considered to be one of possible exogenous etiological factors of ANCA-associated vasculitis, because in exposed subjects, higher ANCA positivity was found. The association between the presence of rheumatoid factor and ANCA (antineutrophil cytoplasmatic antibodies) in subjects exposed previously to silica was studied.
ANCA were determined by indirect immunofluorescence in workers exposed previously to silica for 20.5 years on average: 46 subjects without silicosis, 60 with simple silicosis, 33 with complicated silicosis, and in the control group of 41 persons. Lung functions and renal functions were measured in all the groups studied. Fisher’s exact test was used for the statistical evaluation of the correlation between rheumatoid factor and ANCA.
ANCA positivity was detected significantly more frequently (p<0.01) in the group of workers exposed previously to silica (16.5 %), than in the control group (4.9 %). Rheumatoid factor was positive in 5.0 % of exposed subjects and in 4.9 % subjects of the control group. Among 15 subjects with ANCA positivity, only one had rheumatoid factor positive (11.0 %), 14 subjects had negative rheumatoid factor (89.0 %). In silica-exposed group, two cases of rheumatoid arthritis were detected, no case in the control group. Among five persons with positive rheumatoid factor, four were ANCA negative, one ANCA positive. Correlation between the two parameters was not found.
No association between ANCA positivity and positivity of rheumatoid factor in patients with previous silica exposure was found.
Rheumatoid arthritis, which it is well known as a Caplan′s syndrome in silicotic patients, belongs to ANCA-associated diseases. However, these results show, that ANCA positivity is not associated with the Caplan′s syndrome. Acknowledgement: MSM J/13 111100002 and 111100005.
D. Pelclová, None.