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Abstract
Objective Our study aimed to identify correlations concerning the controversial relationship between serum interleukin (IL)-17A and IL-6 levels and their associations with SLE activity and organ involvement.
Methods We conducted a prospective cohort study of SLE patients between July and November 2022. Serum concentrations of IL-17A and IL-6 were determined with ELISA method. The disease activity was assessed using SLEDAI.
Results We included 88 SLE patients (89.77% women, mean age 51.16 ± 15.37 years-old) with mean disease duration of 10.01 ± 9.36 years; 19.32% had active disease (SLEDAI≥6), while 80.68% had inactive disease. Hematological (68.18%), cutaneous (55.68%), and articular (50%) were the most common manifestations, whereas hypertension (38.64%), osteoporosis (25%) and osteoarthritis (22.73%) were the most prevalent comorbidities. The most frequently reported symptoms were joint pain (76.14%), fatigue (26.14%), xerophthalmia and xerostomia (20.45%). Analysis of the overall group identified mean serum values of 6.32 ± 2.70 pg/ml for IL-17A and 7.46 ± 6.73 pg/ml for IL-6. Mean serum values of IL-6 were higher among patients with active disease (7.30 ± 6.75 pg/ml vs. 8.15 ± 6.80 pg/ml, p = 0.093). In the case of IL-17A, no statistically significant differences were reported depending on disease activity. Interestingly, mean value for IL-6 was higher in male patients (6.87 ± 5.79 pg/ml vs. 12.59 ± 11.50 pg/ml, p = 0,028). We demonstrated a positive correlation between IL-6 and renal involvement (mean serum value for IL-6 of 7.13 ± 4.87 pg/ml) vs. non-renal involvement (7.54 ± 7.11 pg/ml), with statistically significant value. The ROC analysis showed that IL-6 has predictive value for renal involvement in SLE patients (area under the curve = 0.701, p = 0.012, 95% confidence interval 0.551–0.852). A cut-off value of 5.26 has a sensitivity of 68.8% and a specificity of 70% for predicting renal damage in SLE patients (figure 1). No significant statistical difference was identified in IL-17A levels regarding renal involvement.
Conclusions Our findings indicate that serum IL-6 is a promising target for renal involvement. Circulating IL-17A showed no positive relationship with SLE activity. Further investigations are needed to determine their sensitivity and specificity as biomarkers of disease activity.
The area under the curve of the Receiver Operating Characteristic for IL-6 in patients with renal involvement (AUC: area under the curve; Cl: confidence interval)
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