Serum and urine interleukin-17A levels as biomarkers of disease activity in systemic lupus erythematosus

Abstract

Objectives: This study examined the correlations of both serum and urine interleukin-17A (IL-17A) levels with disease activity in systemic lupus erythematosus (SLE). This study was also aimed at determining their sensitivity and specificity as biomarkers of disease activity in SLE.

Methods: A cross-sectional study was performed involving SLE patients (n = 120 patients) from Universiti Kebangsaan Malaysia Medical Centre (UKMMC). Serum and urinary IL-17A levels were determined by immunoassay while disease activity was assessed using Systemic Lupus Erythematosus Disease Activity Index-2000 (SLEDAI-2K) and British Isles Lupus Assessment Group's 2004 index (BILAG 2004) scores. The correlations between serum and urinary IL-17A levels with total SLEDAI-2K and BILAG 2004 scores were determined using bivariate correlation analyses. Receiver operating characteristic curves were calculated to determine their sensitivity and specificity as disease activity biomarkers.

Results: Both serum and urinary IL-17A levels correlated with total scores of BILAG 2004, BILAG renal, BILAG mucocutaneous, and SLEDAI-2K (P < 0.05). Urine IL-17A levels correlated positively with urine protein : creatinine index while serum IL-17 level correlated with the BILAG hematology score (all P < 0.05). The area under curve of serum IL-17A and urine IL-17A with BILAG and SLEDAI scores were low (<0.75).

Conclusion: Despite positive correlations between serum and urine IL-17A with SLE disease activity, both were neither sensitive nor specific as biomarkers to predict active disease. Hence, IL-17 measurement has no role in SLE disease activity assessments and future studies are needed to search for other reliable activity biomarkers.

Keywords: biomarkers; interleukin-17A; nephritis; systemic lupus erythematosus.