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Abstract
Background Some previous studies in Caucasian, Asian, and African-American patients have shown that urine levels of Neutrophil Gelatinase–Associated Lipocalin (uNGAL) and Monocyte Chemoattractant Protein-1 (uMCP-1) were significantly greater in patients with LN. However, information in Mestizo and Afro-Latin American patients is very limited. Our aim was to evaluate diagnostic value of uNGAL and uMCP-1 as potential markers for the diagnosis of LN in Colombian SLE patients
Materials and methods We examined urinary levels of NGAL and MCP-1 in 93 consecutive SLE patients (ACR criteria 1982) from Hospital San Vicente Fundación, at Medellín, Colombia. uNGAL and uMCP-1 were measured by ELISA techniques (R&D system, Minneapolis, USA). In addition, serum Anti-C1q antibodies were measured (Inova, San Diego, USA). Several clinical and serological features were analysed as well as disease activity (SLEDAI). Mann-Whitney tests were used to compare data and Spearman’s rho for correlations. Additionally, ROC curves relating the specificity and sensitivity profiles of the 2 biomarkers were done.
Results Ninety-three SLE patients were recruited (88% female) with median age of 33.6 ± 12.4 years and median disease duration of 11.5 ± 14.8 years. Mestizo (75%) and Afro-Latin American (22%) were majority. One quarter of patients had an early SLE (< 2 years of duration) and 64 were admitted at the time of urine collection. Hematologic disease (89%), arthritis (83%), cutaneous involvement (82%), and renal disease (66%) were among most common manifestations. 63% of patients were positive for anti-C1q. We found significant positive correlation between uNGAL levels and SLEDAI (r = 0.331, p = 0.02) and between uMCP1 with SLEDAI (r = 0.428, p < 0.02) and with uNGAL (r = 0.467, p < 0.0001). uNGAL and uMCP-1 were significantly higher in patients with LN than in patients without LN (53.0 ± 56.3 vs 16.0 ± 16.6 pg/ml, p = 0.001 and 2340.4 ± 4521.4 vs 472.4 ± 596.5, p = 0.015, respectively). uNGAL levels were also significantly higher in patients with active LN (>500 mg proteinuria/24 hrs) than in inactive LN (66.1 ± 61.9 vs 9.0 ± 8.6, p < 0.001). A ROC curve constructed for uNGAL, uMCP-1, and anti-C1q for LN in all SLE patients showed a good level of sensitivity and specificity (Figure 1).
Conclusions Colombian LN patients had 4 times and 5 times higher levels of uNGAL and uMPC-1, respectively than patients without LN. Additionally, uNGAL was significantly higher in patients with active LN. Both markers were correlated with disease activity. A multinational prospective study is ongoing under GLADEL cohort, in order to evaluate those biomarkers in 14 Latin American countries.
Receiver operating characteristic (ROC) curve of urinary NGAL, MCP-1 and anti C1q for the identification of LN (dotted line for uNGAL, solid green line for uMCP-1 and solid red line for anti C1q)
Acknowledgements JA Gómez-Puerta was supported by Colciencias (conv. 656 de 2014). Anti-C1q antibodies were provided by Inova, Werfen, Colombia