Determinants of outcome in ANCA-associated glomerulonephritis: a prospective clinico-histopathological analysis of 96 patients

BACKGROUND

The predictive value of clinical and renal histological features for renal outcome in patients with anti-neutrophil cytoplasmic autoantibody (ANCA)-associated glomerulonephritis was investigated in a prospective analysis of 96 patients with ANCA-associated vasculitis, and moderate renal involvement (creatinine <500 micromol/L).

METHODS

The extent of 39 histological features in 96 biopsies (performed at entry in a clinical trial) was scored by two independent observers, according to a standardized protocol. Age, gender, diagnosis, glomerular filtration rate at entry (GFR0), ANCA-specificity, proteinuria, and treatment of these 96 patients were also taken into account. Treatment was standardized and started after the biopsy was performed. End-points included renal function at 18 months (GFR18), GFR18 corrected for GFR0 (CORGFR18), and the occurrence of relapse or death.

RESULTS

Parameters that most strongly correlated with GFR18 were GFR0 (r = 0.67), interstitial fibrosis (r = -0.45), glomerulosclerosis (r = -0.37), and tubular atrophy (r = -0.36). Parameters that most strongly correlated with CORGFR18 were segmental (r = 0.45) and cellular (r = 0.30) crescents, and fibrinoid necrosis (r = 0.46). None of the clinical and histological features predicted the occurrence of relapse or death. By applying a stepwise linear multiple regression analysis, we designed a formula for the estimation of renal function at 18 months: GFR18 (mL/min) = 17 + 0.71 x GFR0 (mL/min) + 0.34 x fibrinoid necrosis (%) + 0.33 x segmental crescents (%), (r2 = 0.60; standard deviation = 19 mL/min). Our results were independent of diagnosis, ANCA-specificity, and treatment limb.

CONCLUSIONS

These data suggest that in ANCA-associated glomerulonephritis, GFR0 and predominantly chronic renal lesions are potent predictors of GFR18. Active lesions are associated with renal function recovery and may be reversible. The formula for the estimation of GFR18 shows that a combination of GFR0 and renal histology is a better predictor for GFR18 than GFR0 only.

Pulmonary renal syndrome: a 4-year, single-center experience

Pulmonary renal syndrome (PRS), defined as a combination of diffuse pulmonary hemorrhage and glomerulonephritis (GN), represents a severe syndrome for which minimal outcome data are available in the literature. We present a retrospective study of 14 consecutive patients from 1996 to 2000. Mean patient age was 65 +/- 2.1 (SEM) years, and 7 patients were women. At presentation, Po(2) on air was 6.0 +/- 0.5 kPa, and creatinine level was 554 +/- 70 micromol/L. Thirteen patients had systemic vasculitis, and 1 patient had systemic lupus erythematosus (SLE). Five patients were cytoplasmic antineutrophil cytoplasmic autoantibody (C-ANCA) positive, and 7 patients were perinuclear ANCA (P-ANCA) positive; 2 of the latter patients also were positive for anti-glomerular basement membrane antibodies. Renal biopsy was performed in 10 patients. Histological examination showed membranous GN in the patient with SLE and segmental necrotizing crescentic GN in the other 9 patients examined. Twelve of 14 patients were initially dialysis dependent, and 8 of 14 patients required ventilatory support. All patients were treated with corticosteroids, 8 of 14 patients were administered intravenous methylprednisolone, 13 of 14 patients were administered daily cyclophosphamide, and 12 of 14 patients underwent plasma exchange. Patients were followed up for 22 +/- 9 months. Early reduction in cyclophosphamide dosage was required in 9 patients for neutropenia. Seven patients were alive at the end of follow-up, but 5 patients (36%) died in the first month. Of the survivors, 85% and 67% were alive after 1 and 2 years of completed follow-up: 83% and 75% of these survivors were dialysis independent, respectively. Five relapses were seen in 4 patients. One patient died of progressive pulmonary fibrosis. Sepsis was a major factor in 6 of 7 deaths. This patient group was older than those previously reported. Findings confirm previous suggestions that PRS requiring intensive care treatment has high mortality, and early survivors have good 1- and 2-year outcomes. Cyclophosphamide-associated neutropenia and infection were frequent contributors to death, and less toxic alternatives may improve outcome in PRS.

Renal histology in ANCA-associated vasculitis: differences between diagnostic and serologic subgroups

BACKGROUND

Differences in renal histopathology between microscopic polyangiitis (MPA) and Wegener's granulomatosis (WG), and between anti-neutrophil cytoplasm autoantibody (ANCA) test results in patients with ANCA-associated vasculitis may provide insight into the differences in pathogenesis and raise the opportunity of classifying the vasculitides more accurately. The possible differences in histopathology are investigated in this study.

METHODS

We report an analysis of 173 patients with renal disease in microscopic polyangiitis or Wegener's granulomatosis. A total of 173 renal biopsies, performed at diagnosis, were scored by two observers separately, using a previously standardized protocol. Consensus on each biopsy was achieved during a central review.

RESULTS

Normal glomeruli were more common in WG than in MPA (P < 0.001). Glomerulosclerosis was more prominent in MPA than in WG (P=0.003). Interstitial fibrosis (P < 0.001), tubular atrophy (P < 0.001), and tubular casts (P=0.005) were more frequently present and more severe in MPA than in WG. Presence of glomerulosclerosis was more extensive in patients with myeloperoxidase (MPO)-ANCA than with proteinase 3 (PR3)-ANCA (P=0.022). Interstitial fibrosis (P=0.008), tubular necrosis (P=0.030), tubular atrophy (P=0.013), and intra-epithelial infiltrates (P=0.006) were more frequently present and more severe in MPO-ANCA than in PR3-ANCA.

CONCLUSIONS

Glomerulonephritis in relation to MPA has more characteristics of chronic injury at the time of presentation than glomerulonephritis in relation to WG. This difference may be due to a delayed establishment of diagnosis in patients with MPA compared to patients with WG. Both active and chronic lesions are more abundantly present in MPO-ANCA-positive patients than in patients with PR3-ANCA-positivity, which suggests that the pathogenesis of renal disease in these ANCA subsets could be different. Our results also suggest that ANCA test results may be useful in classifying ANCA-associated vasculitides.