MONOCYTE CHEMOATTRACTANT-1 (MCP-1) AS A URINARY BIOMARKER FOR THE DIAGNOSIS OF ACTIVITY OF LUPUS NEPHRITIS IN BRAZILIAN PATIENTS

R. F. Rosa*1, K. Takei2, N. C. Araujo1, S. A. Loduca1, J. C. M. Szajubok1, W. H. Chahade1
1Rheumatology, 2Immunology, Servidor Publico Estadual Hospital, São Paulo, Brazil

Background: Lupus nephritis is a major concern in systemic lupus erythematosus (SLE) and it affects more than 60% of patients during disease progression. Substantional evidence suggests that MCP-1 contribute to kidney injury in the SLE glomerulonephritis.

Objectives: To evaluate urinary MCP-1 as a biomarker of renal activity in Brazilian lupus cohort using the ELISA test and compare it to other activity markers of the disease that are currently employed in clinical practice.

Methods: Sixty female patients with a diagnosis of SLE and kidney involvement in treatment at the Rheumatology Sector of the Servidor Publico Estadual Hospital as well as patients without kidney involvement and a control group participated in the cross-sectional study. Patients were classified with regards to the disease activity based on clinical and laboratory parameters, such as alterations in urinary sediment, proteinuria, kidney function, renal clearance, C3, C4, native anti-DNA, the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and renal SLEDAI. The participants were distributed among four groups: Group 1 (30 lupus patients with kidney involvement in disease activity); Group 2 (30 lupus patients with the kidney condition in remission); Group 3 (15 lupus patients without kidney involvement); and Group 4 (17 apparently healthy individuals as controls). The levels of MCP-1 were measured by using a specific ELISA according to the manufacturer’s protocols (BioSource International Inc.).

Results: The mean MCP-1 (pg/mg creatinin) of Group 1 was significant higher than that of health controls and the others SLE patients (p<0,001). With the aim of applying this test in the detection of LN, a cut-off point was established using the results from the control group. The cut-off obtained was 596,2. Group 1 had a significantly greater frequency of positive results for urinary MCP-1 in comparison to the other groups (p<0,001), demonstrating that this is a promising chemokine for the screening of lupus patients in renal activity. With the aim of detecting disease activity in patients with LN, a new cut-off point was determined based on the results of the lupus patients with kidney involvement in remission. Setting specificity at 90%, the sensitivity of the test was 56.7%.

Conclusion: The determination of this chemokine, using an accessible, easily performed immunoassay, contributes toward the diagnosis of lupus nephritis activity. Associated to other parameters employed in clinical practice, this biomarker represents an advance in the diagnosis and early establishment of adequate treatment for these patients.

References: 1. Tucci M, Calvani N, Richards HB, Quatraro C, Silvestris F. The interplay of chemokines and dendritic cells in the pathogenesis of lupus nephritis. Ann NY Acad Sci. 2005;1051:421-32. 2. Rovin BH, Song H, Birmingham DJ, Hebert LA, Yu CY, Nagaraja HN. Urine chemokines as biomarkers of human systemic lupus erythematosus activity. J Am Soc Nephrol. 2005;16(2):467-73.