Renal arterial resistive index as a noninvasive biomarker of disease activity in lupus nephritis patients

Aim of the workTo evaluate the renal resistive index (RI) in lupus nephritis (LN) patients and to study its association with clinical features, laboratory investigations and LN pathological classes in systemic lupus erythematosus (SLE) patients.Patients and methodsThe study included 45 SLE patients and 25 matched controls. SLE disease activity index (SLEDAI) was assessed and patients subdivided into LN (renal SLEDAI ≥ 4) and no-renal activity (NRA) (renal SLEDAI = 0). Ultrasound Doppler renal examination was done to measure RI. Renal biopsies were performed in 30 LN patients.ResultsThe mean age of patients was 29.8 ± 10.1 years and disease duration 4.3 ± 3.9 years. They were 40 females and 5 males (F:M 8:1). Their SLEDAI was 10.9 ± 8.2 and renal SLEDAI was 5.2 ± 5.1. They were 30 with LN and 15 NRA SLE patients. Renal RI was significantly higher in LN patients compared to NRA SLE patients and controls (0.61 ± 0.04 vs. 0.55 ± 0.01 vs. 0.55 ± 0.02; p < 0.0001). RI significantly correlated with anti-double stranded deoxyribonucleic acid (anti-dsDNA) positivity (r = 0.33, p = 0.03), 24-hour proteins in urine (r = 0.38, p = 0.01) and negatively with creatinine clearance (r = -0.33, p = 0.03). Renal RI significantly correlated with pathological classes of renal biopsy (r = 0.65, p < 0.0001). At renal RI cut-off value 0.57 renal RI can detect renal activity with sensitivity of 83.3%, specificity of 82.5%, p < 0.0001. Renal RI ≥ 0.57 had higher activity index score compared to those with normal RI (5.7 ± 0.6 vs. 9 ± 3.3, p = 0.04). Conclusion: Renal RI was significantly increased in LN compared to NRA patients and was associated with laboratory parameters and pathological classes.