Urine Biomarker Helps Identify and Monitor Proliferative Lupus Nephritis

Lupus nephritis (LN) is usually diagnosed in patients with high disease activity in systemic lupus erythematosus (SLE) using a kidney biopsy and urinary abnormalities, especially elevated CD4 T cells. A study from Germany suggests that high levels of these inflammatory T cells in urine may be more sensitive and specific for active LN than an invasive biopsy or other urinary markers – and can also gauge response to treatment.

The researchers analyzed urine samples from a cross-sectional cohort of 147 SLE patients with and without renal involvement, using 31 patients with other nephropathies (including diabetic nephropathy) and 20 healthy volunteers as controls. A group of 14 SLE patients undergoing treatment were monitored.

Urinary CD4 T cell counts of ≥800/100 ml urine were seen exclusively in SLE patients with both active disease and renal involvement, while very few urinary CD4 T cells could be detected in those without renal involvement whatever their disease activity.

In patients with renal involvement (but not in those without it), the number of urinary CD4 T cells correlated significantly with disease activity as assessed by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Elevated CD4 T cell counts were more specific for LN than for other nephropathies.
 
Patients undergoing therapy whose urinary CD4 T cell counts normalized below 800/100 ml within six months showed a significant reduction in their SLEDAI and better renal function. Those whose counts persisted or increased showed no drop in disease activity and poorer renal function.