Serum interleukin-26 is a promising biomarker in systemic lupus erythematosus patients: Particular relation to disease activity and nephritis

Aim of the work: To investigate the clinical utility of serum interleukin-26 (IL-26) in patients with systemic lupus erythematosus (SLE). Patients and methods: The study was carried out on 42 SLE patients and 42 matched controls. SLE disease activity index 2000 (SLEDAI-2K) and Systemic Lupus International Collaborating Clinics Damage Index (SLICC-DI) were assessed. Serum IL-26 was measured. Results: The mean age of patients was 28.8±11.4 years with 78.6% females. 76.2% of patients were active; 7.1% very-high grade, 45.2% high, 16.7% moderate and 31% mild. 42.9% of patients had nephritis. The mean SLEDAI-2K was 10.4±6.4 and SLICC-DI 1.19±1.15. IL26 level was significantly higher in patients (64±76.4 pg/ml) compared to control (8.7±2.6 pg/ml), in active cases (79.2±81.9 pg/ml) compared to those inactive (15.3±4.8 pg/ml) and in those with nephritis (n = 18) (113.4±92.2 pg/ml) compared to those without (n = 24) (23.1±7.6 pg/ml).IL-26 level was significantly higher among cases receiving both steroids and mycophenolate mofetil than those receiving steroids with azathioprine (p = 0.005). There was a significant negative correlation between IL26 and serum albumin, hemoglobin and complement 3 (C3) levels (p < 0.001, p < 0.001 and p = 0.006 respectively). There was also a significant correlation between IL26 and both SLEDAI-2K (r = 0.95, p < 0.001) and SLICC-DI (r = 0.68, p < 0.001). At cut off value 16.3 pg/ml, IL26 differentiated patients and control; sensitivity 90.5%, specificity 100% (F. 2) and at 20 pg/ml detects active from non-active; sensitivity and specificity 100%. Conclusion: IL-26 is a promising biomarker of SLE with high sensitivity and specificity. There is a relation of IL-26 with disease activity, damage and nephritis.