Clinical characteristics of the SPOCS population at baseline, by SLEDAI-2K and IFNGS category
| Overall (N=823) | SLEDAI-2K | IFNGS | |||||
| <10 (n=343) | ≥10 (n=241) | Nominal p value | High (n=522) | Low (n=217) | Nominal p value | ||
| Years since diagnosis of SLE | n=814 | n=340 | n=238 | 0.012 | n=517 | n=215 | 0.052 |
| Mean±SD | 11.1±9.2 | 12.4±9.6 | 10.4±8.6 | 11.7±9.6 | 10.2±8.6 | ||
| Median (IQR) | 9.0 (4.0–17.0) | 10.0 (5.0–19.0) | 8.0 (3.0–17.0) | 9.0 (4.0–18.0) | 8.0 (3.0–16.0) | ||
| Age at SLE first manifestation, years | n=732 | n=309 | n=223 | 0.522 | n=473 | n=186 | <0.001 |
| Mean±SD | 32.0±13.9 | 31.6±13.9 | 30.8±13.4 | 30.0±12.7 | 36.8±14.6 | ||
| Median (IQR) | 30.0 (22.0–41.0) | 30.0 (20.2–42.0) | 29.0 (22.0–37.0) | 28.0 (21.0–37.0) | 37.5 (25.5–47.0) | ||
| Age at SLE first manifestation, years, n (%) | n=732 | n=309 | n=223 | 0.548 | n=473 | n=186 | <0.0001 |
| <18 | 105 (14.3) | 52 (16.8) | 30 (13.5) | 73 (15.4) | 17 (9.1) | ||
| 18–29 | 245 (33.5) | 101 (32.7) | 83 (37.2) | 181 (38.3) | 43 (23.1) | ||
| 30–49 | 297 (40.6) | 123 (39.8) | 90 (40.4) | 182 (38.5) | 89 (47.9) | ||
| 50+ | 85 (11.6) | 33 (10.7) | 20 (9.0) | 37 (7.8) | 37 (19.9) | ||
| SLE diagnosis age, years, n (%) | n=815 | n=341 | n=238 | 0.297 | n=517 | n=216 | <0.001 |
| <18 | 114 (14.0) | 57 (16.7) | 32 (13.5) | 81 (15.7) | 18 (8.3) | ||
| 18–29 | 231 (28.3) | 91 (26.7) | 77 (32.4) | 180 (34.8) | 31 (14.4) | ||
| 30–49 | 350 (42.9) | 144 (42.2) | 103 (43.3) | 206 (39.8) | 112 (51.9) | ||
| 50+ | 120 (14.7) | 49 (14.4) | 26 (10.9) | 50 (9.7) | 55 (25.5) | ||
| SLEDAI-2K | n=584 | n=343 | n=241 | <0.001 | n=386 | n=135 | 0.101 |
| Mean±SD | 9.8±4.6 | 6.8±1.3 | 13.9±4.5 | 9.8±4.3 | 9.1±4.9 | ||
| Median (IQR) | 8.0 (6.0–12.0) | 7.0 (6.0–8.0) | 12.0 (10.0–16.0) | 8.0 (6.0–12.0) | 8.0 (6.0–10.0) | ||
| SLEDAI-2K ≥10, n (%) | 241 (41.3) | 0 (0.0) | 241 (100.0) | <0.001 | 164 (42.5) | 45 (33.3) | 0.062 |
| Modified SLEDAI-2K* | n=817 | n=343 | n=241 | <0.001 | n=519 | n=217 | 0.174 |
| Mean±SD | 6.5±3.4 | 4.8±1.9 | 8.5±4.2 | 6.2±3.2 | 6.6±3.4 | ||
| Median (IQR) | 6.0 (4.0–8.0) | 4.0 (4.0–6.0) | 8.0 (6.0–10.0) | 6.0 (4.0–8.0) | 6.0 (4.0–8.0) | ||
| Physician Global Assessment | n=820 | n=340 | n=241 | <0.001 | n=520 | n=217 | 0.127 |
| Mean±SD | 1.5±0.6) | 1.4 (0.6) | 1.7 (0.6) | 1.5 (0.6) | 1.5 (0.6) | ||
| Median (IQR) | 1.5 (1.1–2.0) | 1.4 (1.0–2.0) | 1.9 (1.3–2.0) | 1.5 (1.1–2.0) | 1.5 (1.0–2.0) | ||
| SDI total score | n=811 | n=336 | n=237 | 0.100 | n=512 | n=217 | 0.181 |
| Mean±SD | 1.2±1.6 | 1.1±1.4 | 1.3±1.7 | 1.1±1.6 | 1.3±1.6 | ||
| Median (IQR) | 1.0 (0.0–2.0) | 0.5 (0.0–2.0) | 1.0 (0.0–2.0) | 0.0 (0.0–2.0) | 1.0 (0.0–2.0) | ||
| SDI group, n (%) | 0.599 | 0.135 | |||||
| 0 | 386 (47.6) | 168 (50.0) | 109 (46.0) | 258 (50.4) | 92 (42.4) | ||
| 1 | 190 (23.4) | 70 (20.8) | 56 (23.6) | 116 (22.7) | 55 (25.3) | ||
| 2+ | 235 (29.0) | 98 (29.2) | 72 (30.4) | 138 (27.0) | 70 (32.3) | ||
| Any organ damage†, n (%) | 425 (52.4) | 168 (50.0) | 128 (54.0) | 0.344 | 254 (49.6) | 125 (57.6) | 0.048 |
| Annualised flare rate‡ | n=822 | n=343 | n=241 | 0.005 | n=522 | n=216 | 0.666 |
| Mean±SD | 1.5±2.2 | 1.3±2.0 | 1.9±2.4 | 1.5±2.2 | 1.6±2.4 | ||
| Median (IQR) | 2.0 (0.0–2.0) | 2.0 (0.0–2.1) | 2.0 (0.0–2.0) | 2.0 (0.0–2.0) | 2.0 (0.0–2.0) | ||
| ≥1 flare§, n (%) | 445 (54.1) | 175 (51.0) | 155 (64.3) | 0.001 | 287 (55.0) | 113 (52.3) | 0.508 |
| ≥1 mild flare§, n (%) | 187 (22.8) | 95 (27.7) | 43 (17.8) | 0.006 | 124 (23.8) | 44 (20.4) | 0.318 |
| ≥1 moderate flare§, n (%) | 155 (18.9) | 62 (18.1) | 59 (24.5) | 0.060 | 93 (17.8) | 42 (19.4) | 0.603 |
| ≥1 severe flare§, n (%) | 64 (7.8) | 18 (5.3) | 31 (12.9) | 0.001 | 35 (6.7) | 22 (10.2) | 0.107 |
| Conditions or comorbidities, n (%) | n=822 | n=342 | n=241 | n=522 | n=217 | ||
| Any comorbidity | 687/823 (83.5) | 273/343 (79.6) | 205 (85.1) | 0.091 | 426 (81.6) | 192 (88.5) | 0.022 |
| Joint disease (SLE/non-SLE) | 514 (62.5) | 201 (58.8) | 159 (66.0) | 0.078 | 306 (58.6) | 157 (72.4) | <0.001 |
| CVD/stroke risk factors | 276 (33.6) | 102 (29.8) | 74 (30.7) | 0.820 | 160 (30.7) | 92 (42.4) | 0.002 |
| Cancer | 47 (5.7) | 23 (6.7) | 12 (5.0) | 0.382 | 27 (5.2) | 15 (6.9) | 0.352 |
| Renal disease (ESRD) | 96 (11.7) | 43 (12.6) | 30 (12.5) | 0.964 | 74 (14.2) | 14 (6.5) | 0.003 |
| CNS disorders | 86 (10.5) | 24 (7.0) | 34 (14.1) | 0.005 | 51 (9.8) | 26 (12.0) | 0.370 |
| Diabetes mellitus (all) | 63 (7.7) | 31 (9.1) | 14 (5.8) | 0.147 | 32 (6.1) | 28 (12.9) | 0.002 |
| Metabolic syndrome | 20 (2.4) | 8 (2.3) | 6 (2.5) | 0.907 | 6 (1.1) | 13 (6.0) | <0.001 |
| Family history of autoimmune disease | 224/805 (27.7) | 91/327 (27.8) | 72/239 (30.1) | 0.551 | 148/510 (29.0) | 59/213 (27.7) | 0.720 |
All p values are nominal; there have been no adjustments for multiplicity. Subgroups do not total overall population n due to missing data.
*Modified SLEDAI-2K score was defined as the SLEDAI-2K assessment score without the inclusion of points attributable to lupus headache or laboratory results included in the renal, immunological or haematology domains.
†SDI >0.
‡The annualised flare rate is calculated by dividing the number of flares by the follow-up time in days and multiplying by 365.25.
§Physician-reported flares within 6 months of study entry.
ACR, American College of Rheumatology; CNS, central nervous system; CVD, cardiovascular disease; ESRD, end-stage renal disease; IFNGS, type I interferon gene signature; SDI, SLICC/ACR Damage Index; SLEDAI-2K, SLE Disease Activity Index-2000; SLICC, Systemic Lupus International Collaborating Clinics; SPOCS, SLE Prospective Observational Cohort Study.