Table 1.
Patient characteristics.
| Discovery cohort (Sweden) | Replication cohort 1 (USA) | Replication cohort 2 (Denmark/Norway) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SLE | Nephritisa | SLE without nephritis | P valueb | SLE | Nephritisa | SLE without nephritis | P valuesb | SLE | Nephritisa | SLE without nephritis | P valueb | |
| Number of patients (%) | 1091 | 377 (34.6) | 714 (65.4) | 962 | 216 (22.5) | 746 (77.5) | 833 | 354 (42.5) | 479 (57.5) | |||
| Number of females (%) | 941 (86.3) | 290 (76.9) | 651 (91.2) | <0.001 | 883 (91.8) | 184 (85.2) | 699 (93.7) | <0.001 | 746 (89.6) | 305 (86.2) | 441 (92.1) | <0.01 |
| Age at SLE diagnosis, years (mean ± SD) | 35.8 ± 15.9 | 30.7 ± 15.0 | 38.5 ± 15.6 | <0.001 | 35.3 ± 13.4 | 28.2 ± 13.3 | 37.3 ± 12.7 | <0.001 | 32.6 ± 13.5 | 29 ± 12.9 | 35.2 ± 13.4 | <0.001 |
| Disease duration, years (mean ± SD) | 22.3 ± 12.0 | 23.6 ± 11.7 | 21.5 ± 12.0 | <0.01 | 9.19 ± 8.63 | 12.3 ± 9.6 | 8.3 ± 8.1 | <0.001 | 16.6 ± 10.7 | 17.1 ± 11.2 | 16.3 ± 10.4 | 0.29 |
| ACR criteria (mean ± SD) | 5.6 ± 1.4 | 6.2 ± 1.5 | 5.3 ± 1.2 | <0.001 | 4.9 ± 1.5 | 5.9 ± 1.7 | 4.6 ± 1.3 | <0.001 | 5.9 ± 1.4 | 6.5 ± 1.6 | 5.6 ± 1.2 | <0.001 |
|
Class I/II nephritisc, n (%) |
38/278 (13.7) | |||||||||||
| Class III/IV proliferative nephritisd, n (%) | 173/278 (62.2) | 65/118 (55.1) | ||||||||||
|
Class V nephritise, n (%) |
48/278 (17.3) |
|||||||||||
| ESRDf, n (%) | 38/290 (13.1) | 48/216 (22.2) | ||||||||||
aDefined according to the ACR nephritis criteria or as a biopsy confirmed LN in the presence of ANA or anti-dsDNA antibodies, according to the SLICC classification.
bP value for the difference between nephritis and SLE without nephritis. Categorical variables were compared with the χ2 test and continuous variables by student’s unpaired t-test.
cWHO or ISN/RPS 2003 class I or II only, among patients who had undergone renal biopsy and for whom biopsy results were available.
dWHO or ISN/RPS 2003 class III or IV ever, among patients who had undergone renal biopsy and for whom biopsy results were available.
eWHO or ISN/RPS 2003 pure class V, among patients who had undergone renal biopsy and for whom biopsy results were available.
fDialysis or transplantation, among patients with available follow-up data on renal function.
A total of 19/278 patients with available biopsy results had histopathological findings other than a typical LN pattern and classification according to the WHO or ISN/RPS classification systems were not possible.