Læknablaðið : fylgirit - 01.06.1996, Side 63

LÆKNABLAÐIÐ 1996; 82/FYLGIRIT 31
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V-10. A population study on the
prevalence of rheumatoid arthritis in
relation to different rheumatoid
factor isotypes and isotype patterns
Þorbjörn Jónsson, Jón Þorsteinsson, Helgi Valdi-
marsson
Frá Dpts of Rheumatology and Iinmunology, Land-
spítalinn University Hospital, Reykjavík
Elevated rheumatoid factor (RF) is found in a
small proportion of apparently healthy individuals.
However, it has been shown that RF may become
elevated many months or even years before the
clinical onset of rheumatoid arthritis (RA). Further-
more, increased incidence of RA amongst RF posi-
tive healthy individuals has been reported. The ob-
jective of this study was to evaluate the prevalence
of RA in relation to RF isotypes and isotype pat-
terns.
The prevalence of RA was estimated in 135 RF
positive and 194 RF negative individuals, aged 52-80
years, participating in a longitudinal population
based study on the clinical significance of elevated
RF.
Of the 135 RF positive individuals only 26 (19.3%)
had RA compared with seven (3.6%) of the 194 RF
negative subjects (P=0.0001). Of the 26 RF positive
RA patients 20 (77%) had a combined elevation of
IgM RF and IgA RF. A striking finding was that RA
was not more prevalent amongst individuals with an
isolated elevation of IgM RF than amongst the RF
negative subjects (2.6% vs. 3.6%).
These findings indicate that the majority of RF
positive individuals do not have symptoms or signs
of RA. Furthermore, RA is not more common
amongst individuals with isolated elevation of IgM
RF than amongst RF negative subjects. This has to
our knowledge never been reported before.
V-ll. IgA rheumatoid factor
correlates with changes in B- and T-
lymphocyte subsets and disease
manifestations in rheumatoid
arthritis
Þorbjörn Jónsson, Sturla Arinbjarnarson, Kristján
Steinsson, Ásbjörn Sigfússon, Helgi Jónsson, Árni
Jón Geirsson, Jón Þorsteinsson, Helgi Valdimarsson
Frá Dpts of Rheumatology and Immunology, Land-
spítalinn University Hospital, Reykjavík
Elevation of IgA rheumatoid factor (RF) has in
some studies been associated with poor prognosis in
rheumatoid arthritis (RA), including bone erosions
and extra-articular manifestations. The objective of
this study was to analyse the relationship between
different RF isotypes, clinical features and lympho-
cyte subsets in the blood of RA patients.
Ninety five patients with established RA were
evaluated clinically and blood samples collected for
measurement of RF isotypes by ELISA and analysis
of lymphocyte subsets by flow cytometry. Samples
from 22 healthy blood donors were used as controls.
IgA RF positive RA patients had more severe
disease and higher prevalence of extra-articular
manifestations than the other patients. Patients with
raised IgA RF had a higher percentage of CD5 +
B-cells and of CD4+CD45RO+ T-cells compared
with the other RA patients or controls. High per-
centage of CD4+CD45RO+ T-cells was also signif-
icantly associated with extra-articular manifesta-
tions. RA patients with the sicca syndrome had sig-
nificantly higher ratio of CD5+ B-cells than the
other patients.
These findings indicate that different disease
manifestations in RA may not only be associated
with certain RF isotypes but also with changes in
lymphocyte subsets in the blood. The relative in-
crease in CD4+CD45RO+ T-cells in the blood of
IgA RF positive RA patients might reflect a prefer-
ential recruitment of CD8+CD45RO+ T-cells to
inflammatory sites.
V-12. Combined elevation of IgM
and IgA rheumatoid factor is
characteristic for rheumatoid
arthritis
Þorbjörn Jónsson, Kristján Steinsson, Helgi Jónsson,
Arni Jón Geirsson, Jón Þorsteinsson, Helgi Valdi-
marsson
Frá Dpts of Rheumatology and Immunology, Land-
spítalinn University Hospital, Reykjavík
Estimates on the prevalence of raised rheumatoid
factor (RF) isotypes in rheumatoid arthritis (RA)
and other rheumatic diseases have been somewhat
discordant. These differences may be due to differ-
ent methods used for measuring the RF. The ob-
jective of this study was to compare the diagnostic
value of measuring RF by a conventional agglutin-
ation test and individual RF isotypes by ELISA.
Serum samples from 53 patients with RA, 32 with
systemic lupus erythematosus, 18 with scleroderma,
50 with osteoarthritis and 10 with various other rheu-
matic conditions were tested for RF by conventional
agglutination and for IgM, IgG and IgA RF by
ELISA usingrabbit IgG as antigen.
Elevation of one or more RF isotypes was found
in 91% of the RA patients compared with 70% with
conventional agglutination. Corresponding figures
for other rheumatic diseases were 25% and 19%.
About 70% of the RF positive RA patients had
elevation of more than one RF isotype compared
with only 14% of the RF positive non-RA patients.
Combined elevation of IgM RF and IgA RF was