Background: High levels of a protein called soluble CD163 (sCD163) are often seen in patients with a variety of inflammatory conditions, both acute and chronic. This study work aimed to investigate the role of urinary soluble CD163 in evaluation of activity of the disease among patients with SLE.

Methods: We used 90 participants, split evenly between the two groups, in a case-control research. In Group 1, we had 45 individuals with a confirmed case of systemic lupus erythematosus (SLE), and in Group 2, we had 45 individuals who were considered healthy to act as a control. Standard laboratory testing and a comprehensive clinical examination were administered to all subjects. Furthermore, we monitored the activity of sickness in our SLE patients. Using a validated ELISA kit (Sunrise, Tecan), we examined the amounts of sCD163 in the urine of all subjects.

Results: The median of urinary CD163 were significantly higher among the SLE patients (P<0.001). Significant positive correlations were revealed between urinary sCD 163 and SLEDAI-2k (r=0.765, P<0.001), renal SLEDAI (r=0.823, P<0.001), ESR (r=0.766, P<0.001) and 24h urine protein (r=0.436, P=0.003). Urinary CD163 had the highest sensitivity (82.22%) and specificity (93.33%) at a cut-off point of 247.6 among SLE patients with area under the curve (0.859) to discriminate healthy subjects from SLE patients.

Conclusion: Urinary sCD163 could serve as a valuable biomarker for SLE disease activity. It particularly correlates with renal disease activity and can be used for monitoring lupus nephritis