TABLE 1.
Patient characteristics.
| All (n = 284) | Normal Mg (n = 221) | Hypomagnesemia (n = 63) | p | |
|---|---|---|---|---|
| Age, years | 64.0 (48.0–73.0) | 71.0 (51.0–74.0) | 55.0 (38.0–69.0) | 0.029 |
| Male:Female | 46:238 | 35:186 | 11:52 | 0.752 |
| Underlying disease | ||||
| RA (%) | 108 (38.0) | 94 (42.5) | 14 (22.2) | |
| SLE (%) | 59 (20.8) | 36 (16.3) | 23 (36.5) | |
| PM/DM (%) | 20 (7.0) | 11 (4.9) | 9 (14.2) | |
| SSc (%) | 24 (8.5) | 23 (10.4) | 1 (1.6) | |
| MCTD (%) | 10 (3.5) | 9 (4.1) | 1 (1.6) | |
| PMR (%) | 10 (3.5) | 7 (3.2) | 3 (4.8) | |
| Others* (%) | 53 (18.7) | 41 (18.6) | 12 (19.0) | |
| Serum electrolytes | ||||
| Mg, mg/dL | 2.1 (1.9–2.2) | 2.1 (2.0–2.2) | 1.7 (1.7–1.8) | <0.001 |
| Na, mEq/L | 140.9 (139.7–142.3) | 141.2 (139.8–142.4) | 140.5 (139.3–141.9) | 0.163 |
| K, mEq/L | 4.2 (3.9–4.4) | 4.2 (4.0–4.4) | 4.1 (3.9–4.3) | 0.087 |
| CL, mEq/L | 105.0 (104.0–107.0) | 106.0 (104.0–107.0) | 105.0 (103.0–106.0) | 0.241 |
| Ca, mEq/L | 9.2 (8.9–9.4) | 9.1 (8.9–9.4) | 9.2 (8.9–9.4) | 0.608 |
| P, mEq/L | 3.5 (3.2–3.9) | 3.5 (3.2–3.9) | 3.5 (3.1–3.9) | 0.489 |
| Cr, mg/dL | 0.71 (0.61–0.83) | 0.71 (0.60–0.83) | 0.74 (0.63–0.85) | 0.477 |
| eGFR, ml/min/1.73m2 | 68.0 (56.0–80.0) | 63.0 (56.0–80.0) | 70.0 (56.0–81.0) | 0.462 |
| Urine markers | ||||
| β2-microglobulin, ×102μg/L | 1.5 (0.9–2.9) | 2.1 (0.9–3.2) | 1.2 (0.7–1.9) | 0.386 |
| α1-microglobulin, mg/L | 3.3 (1.6–6.5) | 3.8 (1.6–6.9) | 3.3 (1.6–5.8) | 0.636 |
| L-FABP, μg/g･Cre | 2.4 (1.6–4.7) | 3.1 (1.7–4.8) | 2.2 (1.4–4.4) | 0.164 |
| NAG, IU/L | 5.0 (2.5–8.2) | 5.0 (2.4–8.1) | 5.3 (3.4–9.6) | 0.120 |
| NGAL, μg/g･Cre | 21.7 (14.0–38.5) | 21.7 (15.1–37.1) | 21.7 (12.9–46.0) | 0.770 |
| Medication | ||||
| GC, (%) | 118 (41.5) | 78 (35.3) | 40 (63.4) | 0.001 |
| GC dose, median (IQR) mg/day | 0 (0–4) | 0 (0–3) | 3 (0–5) | 0.001 |
| TAC (%) | 68 (23.9) | 34 (15.3) | 34 (53.9) | 0.001 |
| TAC dose, median (IQR) mg/day | 3.0 (1.5–3.0) | 2.0 (1.0–3.0) | 3.0 (2.5–3.0) | 0.037 |
| MMF (%) | 13 (4.6) | 6 (2.7) | 7 (11.1) | 0.006 |
| MTX (%) | 81 (28.5) | 71 (32.1) | 10 (15.9) | 0.001 |
| AZA (%) | 19 (6.7) | 17 (7.6) | 2 (3.2) | 0.213 |
| HCQ (%) | 27 (9.5) | 13 (5.9) | 14 (22.2) | 0.001 |
| PPI (%) | 141 (49.6) | 93 (42.1) | 48 (76.1) | 0.001 |
| Hospitalization due to infection | 25 (8.8) | 15 (6.7) | 10 (15.8) | 0.042 |
| Respiratory infection (%) | 18 (6.3) | 11 (4.9) | 7 (11.1) | 0.085 |
| Urinary tract infection (%) | 4 (1.4) | 2 (1.0) | 2 (3.2) | 0.607 |
| Skin infection (%) | 3 (1.1) | 2 (1.0) | 1 (1.6) | 1.000 |
Results show median (interquartile range) unless otherwise indicated.
Others include microscopic polyangiitis, IgG4-related disease, Sjogren’s syndrome, adult Still’s disease, arthritis with palmoplantar pustulosis, eosinophilic granulomatous polyangiitis, psoriatic arthritis, sarcoidosis, Takayasu’s arteritis, granulomatous polyangiitis, Behçet’s disease, diffuse fasciitis, and familial Mediterranean fever.
Mg, magnesium; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus; SSc, systemic sclerosis; MCTD, mixed connective tissue disease; PMR, polymyalgia rheumatica; Cr, creatinine; eGFR, estimated glomerular filtration rate; L-FABP, liver-type fatty acid binding protein; NAG, N-acetyl-β-D-glucosaminidase; NGAL, neutrophil gelatinase-associated lipocalin; GC, glucocorticoid; PPIs, proton pump inhibitors; TAC, tacrolimus; MMF, mycophenolate mofetil; MTX, methotrexate; AZA, azathioprine; HCQ, hydroxychloroquine.