Urine Plasmin Identified as Strong Biomarker for Lupus Nephritis Diagnosis

Plasmin in the urine has been identified as the strongest predictor of estimated glomerular filtration rate (eGFR) and clinical renal disease in patients with lupus nephritis (LN).

Lupus nephritis is an inflammation of the kidneys caused by the autoimmune disease systemic lupus erythematosus (SLE). It is a type of glomerulonephritis in which the glomeruli become inflamed. LN is one of the most frequent and severe clinical manifestations of SLE, representing a leading cause of kidney failure and death.

Renal biopsy is the standard method used for the diagnosis and prognosis of LN, but it is an invasive technique that cannot be used for routine monitoring of disease activity and treatment responses. As part of a project to identify biomarkers to diagnose LN, investigators at the University of Houston (Texas, USA) evaluated the utility of urinary pro-thrombotic molecules such as tissue factor (TF), anti-thrombotic molecules such as tissue factor pathway inhibitor (TFPI), and fibrinolytic molecules such as plasmin and d-dimer.

For this study, ELISA tests were used to measure levels of d-dimer, plasmin, TF, and TFPI in urine samples obtained from 113 biopsy-proven LN patients (89 active LN and 24 inactive LN), 45 chronic kidney disease patients, and 41 healthy controls.

Results revealed that urine plasmin was the strongest independent predictor of eGFR (which describes the flow rate of filtered fluid through the kidney) and renal disease status. Plasmin is a vital enzyme present in blood that degrades many blood plasma proteins, including fibrin clots.

"Among the proteins examined, urine plasmin emerged as the strongest independent predictor of kidney function and renal disease status," said senior author Dr. Chandra Mohan, professor of biomedical engineering at the University of Houston. "Urine biomarkers represent promising candidates for the early diagnosis as well as the monitoring of disease activity and therapeutic responses in lupus nephritis. The discovery of the new biomarker for active LN opens the door for clinical monitoring of the disease."

The study was published in the July 18, 2019, online edition of the journal Arthritis Research and Therapy.

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