Clinical significance of urinary soluble CD11b and CD163 receptor levels in ANCA-associated vasculitides

Objective. To assess the diagnostic value of urinary soluble CD11b and CD163 receptor levels (U-CD11b and U-CD163) in patients with antineutrophil cytoplasmic antibody-associated systemic vasculitides (AAV). Material and methods. This cross-sectional study included 48 patients (21 men, 27 women; median age 52 [31; 67] years) with a confirmed diagnosis of AAV: granulomatosis with polyangiitis (GPA) in 38, microscopic polyangiitis (MPA) in 8, and eosinophilic granulomatosis with polyangiitis in 2. Patients were stratified into two groups: Group 1, AAV without kidney involvement (n=25); Group 2, AAV with kidney involvement (n=23). A comparison Group 3 comprised 13 patients with systemic lupus erythematosus (SLE) and biopsy-proven kidney involvement (4 men, 9 women; median age 34 [29.0; 43.4] years). All patients underwent standard clinical, laboratory, and instrumental evaluations. U-CD11b and U-CD163 were measured by ELISA using kits ELH-ITGAM-1 (human CD11b) and DC1630 (human CD163) (China). Reference values for U-CD11b and U-CD163, established as the 95th percentile in volunteers without autoimmune disease, were 5.7 and 41.4 ng/mL, respectively. In 10 patients (2 with GPA, 1 with MPA, and 7 with SLE) glomerulonephritis (GN) was verified by vital renal biopsy. Results and discussion. GN was identified in 36 patients (23 with AAV, 13 with SLE). U-CD11b level was significantly higher in 8 (61.5%) SLE patients than in 22 (46%) AAV patients (median 8.2 [4.5; 11.1] and 5.1 [2.7; 8.1] ng/mol, respectively; p=0.02). Conversely, U-CD163 level was higher in 13 (48%) AAV patients (median 29.8 [3.5; 159.1] ng/mmol) than in 6 (46.1%) SLE patients (22.6 [12.7; 148.5] ng/mol), p=0.04. Elevated U-CD11b was detected more frequently in SLE and in AAV with kidney involvement than in AAV without kidney involvement (61.5%, 56.5%, and 36%, respectively; p=0.001), with the highest median in Group 3 (median 8.2 [4.5; 11.1] ng/mmol). Elevated U-CD163 was more frequent in Groups 3 and 2 than in Group 1 (46.1%, p=0.009; 43.4%, p=0.025; and 12%, respectively), with the highest median in Group 2 (34.9 [9.3; 159.1] ng/mmol). However, between-group differences in the frequencies of elevated U-CD11b and U-CD163 were not statistically significant. In Group 1, increases in U-CD11b (36% of cases) and U-CD163 (12%) levels were also observed. Elevated biomarker levels were associated with higher disease activity but not with GN morphological classes in AAV or SLE. Conclusion. U-CD11b and U-CD163 levels may reflect the severity of renal inflammatory involvement in patients with AAV and SLE. Further studies are needed to determine the diagnostic utility of these biomarkers.