Læknablaðið : fylgirit - 01.05.1978, Page 28

A. Kolbeinsson, E. AUander, O. Björnsson,
O. Olafsson, N. Sigfússon, J. Thorsteinsson.
Intr oduction:
In a long term population study, which was
started in 1967 by the Icelandic Heart Associ-
ation, the prevalence and incidence of RF in the
population of Reykjavik and suburbs was investi-
gated. The RF is considered as a risk factor
and information on its prevalence and incidense
is of epidemiological significance. The knowledge
in this field may also contribute to better under-
standing of the nature of the rheumatoid arthritis.
Mater ial:
The population selected for this study, both
men and women, were divided in three groups
for either sex, labeled A, B and C (see table I).
The selection was based on date of birth, this
the group B consisted of women borne on the
1., 4., 7., 10. etc. day of each month.
There were apprax. 3000 people in each group.
The first stage of investigation was performed
from the fall '68 to the fall '69. This stage
consisted of the B group (women) and the response
was 707o.
The second stage of the investigation was
performed three years later '71 - '72. Then
the group B was investigated second time and
the group C for the first time. The response in
the second investigation of women was 74%. The
total number of sera investigated for rheumatoid
factor was 4093 (1% of the sera collected were
not investigated for RF.)
Table II shows in the first column the 6 age
groups of women according to date of birth,
devided into five year intervals, in the second
stage of investigation (1971). The highest number
of participants are in the two middle age groups.
In the third column of the table is the number
of women investigated in group B, first and
second stage and in group C investigated for the
first time at the second stage of this study. ,
(1971). Most of the women in the B group at
the second stage were investigated for second
time, but some for the first time (those who did
not respond to invitation to the first stage of the
study).
M ethods:
Two methods were used for determining the
THE PREVALENCE AND
INCIDENCE OF RHEUMATOID
FACTOR (RF) AMONG FEMALE
POPULATION IN ICELAND
RF. Both Waaler-Rose (WR) and akrylfixation
test (AFt). Right after collection the sera were
frosen down and stored at minus 22C. The
storage time of sera varied from 6 months to
30 months. Two technicians performed the test
for RF. One did the first stage and the other
the second stage. Two sera with positive WR
titer were used as controls. These controls
were compared with an intemational reference
preparation of RF serum obtained from
Statens Seruminstitut Copenhagen.
R esults:
Results from the first stage of this study has
been published and this paper deals with results
from investigation of RF in group B and C
females in the second stage of the study.
Diagram III. shows the prevalence of Waaler
Rose titer equal or gradet 1/20 in the two groups
of women. Group B first stage and Group B-C
second stage. The intermitted line in this
diagram shows the results from the first stage
Group-B and the solid line the results from the
second stage. Group B-C. These curves show
the prevalence of RF show similar trends and
the prevalence of R F increases with age.
Diagram IV. shows the prevalence of AFT titer,
equal or greater than 1/20 in the same way and
in the same groups as diagram III shows the
WR titer. The curves from first and second
stage do not agree in the same way as the
curves for WR titer did. The curve from first
stage is 1/2-1% lower than the curves from
second stage. This may be explained by the
fact that two different technicians performed the
AFT tests at each stage, and the tests are rather
difficult to read.
Table V. shows the changes in WR titers from
positive to negative reaction. In this table the
lowest positive titer is 1/10. 35 were positive
in the first stage and 34 were positive in second
stage. From 1734 negatives in first stage 19
were positive or 140 in the second stage.
The estimated age conditioned yearly brutto
incidence of RF in this population will be approxi-
mately 0. 3%. Compared to the yearly aged
condition netto incidence of RF 0.1%.
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