Interstitial inflammation and interstitial fibrosis and tubular atrophy predict renal survival in lupus nephritis

BACKGROUND: This study examines the effect of interstitial inflammation and interstitial fibrosis and tubular atrophy on renal survival in lupus nephritis. METHODS: Baseline characteristics, initial (n = 301) and repeat biopsies (n = 94) and clinical outcomes for patients with biopsy-proven lupus nephritis from 1998 to 2014 were retrospectively collected from the medical record. Clinical and morphologic variables were evaluated using a Cox proportional hazards model and multiple imputation to address missing data. Renal survival was defined as the time from initial biopsy to end-stage renal disease [estimated glomerular filtration rate (eGFR) <15 mL/min/1.73 m(2)], dialysis or transplant. RESULTS: A total of 218 patients had follow-up and Class IV had worse renal survival, especially in patients with active and chronic glomerular lesions {relative to non-IV; Class IV-A: hazard ratio [HR] 0.92 [95% confidence interval (CI) 0.41–2.04], Class IV-AC: HR 5.02 [95% CI 2.70–9.36]}. Interstitial inflammation grade [relative to interstitial inflammation <5%; interstitial inflammation 5–25%: HR 2.36 (95% CI 1.13–4.91), interstitial inflammation 25–50%: HR 3.84 (95% CI 1.53–9.62), interstitial inflammation >50%: HR 7.67 (95% CI 3.75–15.67)] and increased interstitial fibrosis and tubular atrophy (IFTA) category [relative to IFTA <5%; IFTA 5–25%: HR 3.93 (95% CI 1.58–9.75), IFTA 25–50%: HR 4.01 (95% CI 1.37–11.70), IFTA >50%: HR 13.99 (95% CI 4.91–39.83)] predicted worse renal survival among all patients and those with Class IV on initial and repeat biopsy (n = 94) in a dose-dependent manner. Interstitial inflammation grade and IFTA category were significant predictors of renal survival in a multivariable model adjusted for age, gender, race, ethnicity and serum creatinine. CONCLUSIONS: Interstitial inflammation and IFTA independently affect renal survival and grading these lesions stratifies risk within the International Society of Nephrology and Renal Pathology Society classification of lupus nephritis.