Abstract
To assess the level of β2-microglubulin (β2M) in systemic lupus erythematosus (SLE) patients and its association with disease activity and other disease parameters.
40 SLE patients and 22 matched controls were studied. Serum β2M was assessed using enzyme-linked immunosorbent assay (ELISA). SLE Disease Activity Index (SLEDAI) and the damage index were assessed.
The patients were 36 females and 4 males (F:M 9:1) with a mean age of 28.5 ± 7.9 years and disease duration of 6.7 ± 3.3 years. The SLEDAI was 9.3 ± 5.2 and the damage index 1.83 ± 1.84. The mean level of serum β2M was significantly higher in SLE patients (6.42 ± 2.46 mg/L) than control (2.47 ± 0.4 mg/L) (p < 0.01).The serum level of β2M was significantly higher in patients with nephritis (n = 22) (7.45 ± 2.47 mg/L) compared to those without (n = 18) (5.17 ± 1.82 mg/L)(p = 0.002), And it was similar in those with and without arthritis (7.24 ± 2.3 mg/L vs 5.88 ± 2.4 mg/L (p0.07).The β2M significantly correlated with disease activity (r = 0.86, p 0.001), serum creatinine (r = 0.52, p > 0.001), urea (r = 0.63, p < 0.001), 24 h urinary protein (r = 0.56, p < 0.001), hematuria (r = 0.4, p < 0.01) and pyuria (r = 0.41; p < 0.01), ESR (r = 0.48; p < 0.01) and inversely with hemoglobin level (r = −0.34; p = 0.03). No significant correlation was found with C-reactive protein or with disease damage. Serum (β2M) significantly predicted nephritis and disease activity (sensitivity 63.6 %, specificity 77.8 %; p < 0.001 and 95 %CI: 0.25–0.41; p < 0.001 respectively).
Serum β2M is significantly associated with disease activity and lupus nephritis, suggesting that serum β2M may serve as a potential biomarker to monitor the disease activity and predicting lupus nephritis. However its association to disease severity needs further longitudinal studies.