Renal Function at Biopsy Is Key
Study of lupus nephritis patients also finds link between baseline platelet counts and ESRD.
WASHINGTON, D.C.—The best predictor of outcome in patients with lupus nephritis is kidney function at the time of renal biopsy, supporting the need for early diagnosis and treatment, researchers reported here at the American College of Rheumatology annual meeting.
The study also showed that biopsy findings are associated with elevated platelet counts, which may reflect systemic response to inflammation in active, proliferative disease.
Clinicians lack adequate tools to predict outcomes in lupus nephritis patients, said Jim Oates, MD, associate professor of medicine at the Medical University of South Carolina in Charleston. The literature suggests that the most powerful predictors of outcomes are serum creatinine and the level of glomerular fibrosis at baseline, said Dr. Oates. An ideal marker, he said, clearly should not rely on existing renal damage to predict outcomes.
He and his colleagues studied 126 patients (including 91 African Americans) with systemic lupus erythematosus (SLE) who had biopsies performed over 10 years as part of routine care. Biopsies were graded according to the World Health Organization (WHO) classification scheme and given an activity index score (a marker of inflammation) and a chronicity index score (a marker of sclerosis).
Investigators blindly scored subendothelial deposits found on electron microscopy. The nadir serum creatinine (lowest between biopsy and final reading) and latest available serum creatinine (averaged 4.3 years later), the presence of end-stage renal disease (ESRD), and the therapeutic regimens used for lupus nephritis were determined by chart review.
ESRD was more likely to develop in patients with proliferative lupus nephritis. Subendothelial deposit scores were not associated with clinical outcomes. The only predictors of ESRD were chronicity index on biopsy, platelet count at baseline, and nadir serum creatinine. Additionally, use of cyclophosphamide was associated with worsening of renal damage.
The researchers observed no significant differences in outcomes between Blacks and Caucasians.
The study is the first to reveal an association between higher platelet counts with ESRD, Dr. Oates said. “This may be a marker of an inflammatory response,” he explained. “It has been shown that platelets are not benign actors that simply form clots. It may be that platelets are playing an active role in proliferation or sclerosis in lupus nephritis. The association between high chronicity index and ESRD indicates that patients who were biopsied after disease had progressed to sclerosis had worse outcomes. Avoiding the ‘wait-and-see' approach with your patients with lupus nephritis is the most important message from our study.”