Univariate analysis of putative clinical and laboratory predictors of bone mineral density (BMD)
| Low BMD (N=12) | Normal BMD (N=68) | OR (95% CI) | |
|---|---|---|---|
| Baseline characteristics | |||
| Mean BMI z score at diagnosis (SD) | −0.99 (1.02) | 0.09 (0.95) | 0.35 (0.18 to 0.69)* |
| Ethnicity: Asians (%) | 5 (42) | 24 (35) | 1.31 (0.38 to 4.57) |
| Postpubertal patients (%) | 9 (75) | 52 (76) | 0.92 (0.22 to 3.83) |
| Disease characteristics | |||
| Nephritis (%) | 5 (42) | 16 (24) | 2.32 (0.65 to 8.33) |
| Central nervous system (%) | 2 (17) | 9 (13) | 1.31 (0.25 to 6.98) |
| Disease activity | |||
| Median SLEDAI (range) | 13.5 (7–32) | 10.5 (2–43) | 2.46 (0.87 to 6.95) |
| Median ECLAM (range) | 6.5 (4–10) | 5 (0–11) | 2.93 (0.75 to 11.46) |
| Treatment | |||
| No corticosteroid (%) | 5 (42) | 17 (25) | 0.47 (0.13 to 1.67) |
| Median cumulative steroid dose up to DEXA (mg/kg (range)) | 8.2 (0–68.5) | 22.5 (0–115.5) | 1.21 (0.51 to 2.86) |
| Hydroxychloroquine (%) | 4 (33) | 23 (34) | 0.98 (0.27 to 3.59) |
| Any immunosuppressive agent (%) | 1 (8) | 18 (26) | 0.25 (0.03 to 2.10) |
| Laboratory tests | |||
| Median C3 (g/l (range)) | 0.62 (0.17–1.17) | 0.81 (0.15–1.98) | 0.69 (0.29 to 1.66) |
| Median C4 (g/l (range)) | 0.12 (0.04–0.18) | 0.12 (0.01–0.76) | 0.91 (0.43 to 1.91) |
| Median ESR (mm/h (range)) | 76 (1–135) | 45 (1–140) | 1.19 (0.73 to 1.93) |
| Laboratory assessment of bone health | |||
| Median iPTH (ng/l (range)) | 43 (21–64) | 29 (3–129) | 2.01 (0.45 to 9.00) |
| Median calcium (mmol/l (range)) | 2.36 (2.18–2.51) | 2.40 (2.01–2.73) | 0.14 (0.001 to 15.35) |
| Median ionised calcium (mmol/l (range)) | 1.22 (1.10–1.27) | 1.21 (0.86–1.32) | 1.69 (<0.001 to >999.99) |
| Median phosphate (mmol/l (range)) | 1.31 (0.74–1.67) | 1.33 (0.82–1.89) | 0.60 (0.02 to 17.09) |
| Median 25 hydroxyvitamin D (nmol/l (range)) | 37 (25–72) | 40 (10–134) | 1.13 (0.19 to 6.58) |
| Median alkaline phosphatase (U/l (range)) | 115 (81–169) | 77 (37–311) | 4.11 (0.72 to 23.52) |
| Median alkaline phosphatase bone isozyme (U/l (range)) | 69 (49–100) | 36 (15–299) | 2.44 (0.70 to 8.44) |
| Median urine N-telopeptide (nmol BCE/mmol creatinine (range)) | 104 (65–179) | 110 (38–553) | 0.76 (0.17 to 3.50) |
↵* Significant p value was bolded (p=0.003 for BMI by univariate analysis).
BCE, bone collagen equivalent, BMI, body mass index; DEXA, dual energy x-ray absorptiometry; ESR, erythrocyte sedimentation rate; iPTH, intact parathyroid hormone; SLEDAI, Systemic Lupus Erythematosus Disease Activity Index.