Systemic lupus erythematosus and rheumatoid arthritis

Table 5.
Demographic data for the different case-control materials 
Paper I – III*
(SLE) 
Paper IV
(pre-RA) 
Paper V 
(early-RA) 
Patients 
Controls 
Pre-Pat. 
Controls Patients Controls 
Individuals, 
n 260 670 92 368 769 1054 
% 
Women 
84.6 73.1 75.0 75.0 67.7 73.7 
Age at inclusion, 
mean ± SD, yrs 
- 61.1±12.1 
52.7±9.0 
52.6±9.0 - 57.3±11.6 
Age at onset, 
mean ± SD, yrs 
39.0±15.7 - 
- 
- 55.4±14.0 - 
Disease duration, 
mean±SD 
12.4±9.7 
1
- - - 
6.8±4.1 
2
- 
* Data on patients from mid- and southern Sweden from paper III is not included 
1 
– years, 
2 
- months
Individuals before onset of any symptoms of RA and controls (Paper IV) 
Among the RA patients with early diagnosed disease at the Department of 
Rheumatology, University Hospital, Umeå, 92 individuals who had donated 
blood samples before any symptoms of joint disease were identified and 
matched with 368 controls (Figure 9). 
Figure 9.
Illustration of the sampling of pre-patients and controls 
For every case (
i.e.
, pre-patient) four controls were randomly selected from 
within the registers of the Medical Biobank of Umeå, and matched for sex, age 
at the time of blood sampling, and for rural or urban residence. The median 
sampling time before onset of symptoms of joint disease was 2.4 years [inter 
quartile range (IQR) 1.2-4.9 years]. On average, the diagnosis of RA was 
established 7.8 (IQR 5-10) months after the first symptoms of joint disease. The 
- 37 -

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mean age at the onset of disease was 56.0 years, range 37–68 years. 
Demographic data is presented in Table 5. 
 
The early RA case-control material (Paper V) 
The early RA case-control material comprised patients with early diagnosed 
RA, 
i.e.
, with a disease duration <12 months, fulfilling the ACR criteria for 
RA.
60
The patients were consecutively included from the four northern-most 
counties in Sweden. The population-based controls were geographically 
matched with the patients and derived from the Medical Biobank of the 
Northern Sweden. The demographic data is presented in Table 5.