Composite Biomarker Can Track Inflammation in Lupus Nephritis

A combination of three biomarkers may be useful for monitoring interstitial inflammation in patients with lupus nephritis, according to a report in Kidney International.

The researchers collected urine samples from 61 patients with lupus nephritis, at or around the time of renal biopsy. All patients met at least four American College of Rheumatology criteria for systemic lupus erythematosus, including immune complex glomerulonephritis. A renal pathologist graded interstitial inflammation and interstitial fibrosis in 64 biopsy specimens. Linear discriminant analysis was performed to evaluate various urinary biomarkers for inclusion in a “composite biomarker” of interstitial inflammation.

The composite biomarker of tubulointerstitial inflammation consisted of monocyte chemotactic protein-1; hepcidin, which reflects lupus nephritis flares; and liver fatty acid–binding protein. Sensitivity was 100 percent, specificity 81 percent, positive predictive value 67 percent, and negative predictive value 100 percent. The composite biomarker had a misclassification rate of only 14 percent.

Renal biopsy is typically performed at diagnosis of lupus nephritis but not for subsequent disease flares. An accurate, noninvasive indicator of kidney injury—particularly interstitial inflammation—would be helpful in planning and monitoring medical treatment.

The new composite biomarker shows promise for use in monitoring tubulointerstitial inflammation in lupus nephritis. Although further validation is needed, the authors believe that the biomarker could provide useful information about the renal interstitium in other kidney diseases as well [Zhang X, et al. A composite urine biomarker reflects interstitial inflammation in lupus nephritis biopsies. Kidney Int 2012; 81:401–406].