Table 2.
Baseline Characteristics of Follow-up Study Population and Odds Ratio of Transitioning to SLE Stratified by Enrollment in First or Second Phase of Recruitmenta.
| First Phase of Recruitment (N=375) | Second Phase of Recruitment (N=61) | |||||||
|---|---|---|---|---|---|---|---|---|
| Variable (N, %) | Transitioned to SLE N=22 |
Did Not Transition N=353 |
p-valueb | Unadjusted Orc (95% CI) | Transitioned to SLE N=34 |
Did Not Transition N=27 |
p-valueb | Unadjusted ORc (95% CI) |
| Age at baseline in yearsd: mean (median) ± sd | 47.0 (48.5) ± 13.5 | 47.1 (48.0) ± 16.0 | (0.9) | 1.0 (0.9–1.1) | 47.6 (48.5) ± 11.4 | 48.2 (49.0) ± 12.4 | 0.83 | 1.0 (0.9–1.1) |
| Time between contact in yearsd: mean (median) ± sd | 7.7 (6.7) ± 4.4 | 6.5 (5.8) ± 3.9 | 0.18 | 1.1 (1.0–1.2) | 4.8 (4.6) ± 2.3 | 4.0 (3.1) ± 3.0 | 0.21 | 1.1 (0.9–1.4) |
| Sex: Female | 20 (90.9%) | 293 (83.0%) | 0.33 | 2.1 (0.5–9.1) | 29 (85.3%) | 23 (85.2%) | 0.99 | 0.9 (0.2–3.4) |
| Race: | 0.52 | 0.20 | ||||||
| European American | 17 (77.3%) | 264 (74.8%) | 1 | 26 (76.5%) | 15 (55.6%) | 1 | ||
| African American | 3 (13.6%) | 49 (13.9%) | 0.96 (0.3–3.5) | 6 (17.6%) | 6 (22.2%) | 0.8 (0.3–2.7) | ||
| Othere | 2 (9.1%) | 40 (11.3%) | 0.8 (0.3–2.7) | 2 (5.9%) | 6 (22.2%) | 0.3 (0.06–1.7) | ||
| Relationship to SLE | 0.18 | 0.45 | ||||||
| Proband: | ||||||||
| FDR: Sister | 10 (45.4%) | 166 (47.0%) | 1.3 (0.5–3.8) | 14 (38.2%) | 5 (18.5%) | 2.8 (0.3–25.5) | ||
| Brother | 2 (9.1%) | 27 (7.6%) | 1.7 (0.3–8.6) | 1 (0.3%) | 1 (3.7%) | 1.0 (0.03–29.8) | ||
| Child | 4 (18.2%) | 21 (5.9%) | 4.3 (1.1–16.3) | 3 (8.8%) | 4 (14.8%) | 0.8 (0.06–8.8) | ||
| Parent | 6 (27.3%) | 134 (38.0%) | 1 | 2 (5.9%) | 2 (7.4%) | 1 | ||
| SDR and more distant relative | 0 (0.0%) | 5 (1.4%) | NA | 14 (41.2%) | 15 (55.5%) | 0.9 (0.1–7.6) | ||
| Highest Level of Education Baseline: | 0.008 | 0.74 | ||||||
| > High School | 9 (40.9%) | 234 (66.3%) | 0.3 (0.1–0.7) | 24 (70.6%) | 18 (66.7%) | 1.2 (0.4–3.6) | ||
| ANA Positive Baselinef | 18 (81.8%) | 161 (45.6%) | 0.001 | 5.4 (1.8–16.2) | 25 (73.5%) | 22 (81.5%) | 0.46 | 0.6 (0.2–2.2) |
| SLE-CSQ Categories at Baseline: | <0.0001 | 0.55 | ||||||
| Unlikely SLE | 3 (13.6%) | 245 (69.4%) | 1 | 2 (5.9%) | 3 (11.1%) | 1 | ||
| Possible SLE | 3 (13.6%) | 36 (10.2%) | 6.8 (1.3–34.4) | 2 (5.9%) | 3 (11.1%) | 1.0 (0.1–12.6) | ||
| Probable SLE | 16 (72.7%) | 72 (20.4%) | 18.2 (5.2–63.7) | 30 (88.1%) | 21 (77.8%) | 1.8 (0.3–11.0) | ||
| Number of ACR Criteria at Baseline: | <0.0001 | 0.14 | ||||||
| 0–1g | 6 (27.3%) | 289 (77.1%) | 1 | 1 (2.9%) | 2 (7.4%) | 1 | ||
| 2 | 7 (31.8%) | 56 (15.9%) | 6.0 (2.0–18.4) | 16 (47.1%) | 18 (66.7%) | 0.8 (0.2–3.0) | ||
| 3 | 9 (40.9%) | 8 (2.3%) | 53.7 (16.1–178.6) | 17 (50.0%) | 7 (25.9%) | 2.2 (0.7–6.5) | ||
Significant differences noted in bold. ANA, anti-nuclear antibodies. CSQ, Connective Tissue Disease Screening Questionnaire. ACR, American College of Rheumatology. OR, odds ratio. CI, confidence interval.
For the first phase, we sent letters to 3544 individuals who reported a family member with SLE that was confirmed with medical records. For the second phase, we sent letters to 279 individuals for whom their family member’s SLE was not confirmed, and preferentially selecting individuals who had 2–3 confirmed ACR criteria at their baseline visit.
T-tests for continuous variables and chi-square tests for categorical variables were used to determine differences between individuals who transitioned to SLE and individuals who did not transition to SLE.
Odds ratios for transitioning to SLE were calculated accounting for correlation within families.
Age and time between contact: OR is presented for a 5-year increase
Other includes Native American, Hispanic, and Asian/Pacific Islander.
ANA positivity: ≥ 1:120 titer by indirect immunofluorescence (IIF) on HEp-2 cells.
The bottom 2 categories (0 and 1) for number of ACR criteria were combined as no individuals in the transitioned group had 0 ACR criteria at baseline.