Background A new histopathological classification was developed to predict renal outcome in AAV nephritis1.
Objectives We aimed to investigate the relationship between histopathological findings and renal outcome by using this new classification.
Methods Forty-three AAV patients (60% GPA, 40% MPA) diagnosed according to CHCC and followed-up between 2000-2013 and were included into the study. Demographic, clinical and treatment characteristics were recorded into a predefined protocol. Cyclophosphamide and pulse/high dose methylprednisolone was used in remission induction for at least 6 months in all patients. Renal biopsy specimens including ≥10 glomeruli at diagnosis were evaluated by two pathologists (IK, YO) by using new AAV nephritis histopathologic classification. e-GFR at 0, 6th, 12th, 24th, 60th months were calculated with MDRD formula. Mann Whitney U test was used to compare the e-GFR at 0, 6th, 12th, 24th and 60th months within histopathological subgroups. Correlation of the percentage of the normal glomeruli number and the difference between initial and each follow-up e-GFR values in subgroups were tested by Spearman analysis.
Results Demographic features of AAV cohort (51% women) were as follows: Mean age at diagnosis was 47,5±14,9 (17-75) (median 49) and total disease duration was 59±41 months (median 53). ANCA testing was positive in 93% (c-ANCA 67%, p-ANCA 27%, c-ANCA/anti-PR3%30, p-ANCA/anti-MPO %14). Kidney was the only involved organ in 25% of cohort. Ten (23%) patients had pulmonary-renal syndrome. Mean disease activity score (BVAS03) was 20±6 (0-38). Four patients died (1 acute renal failure, 1 malignancy, 2 sudden death). The AAV cohort was classified as focal (FS) (37%), crescentic (CS) (40%) and mixed (MS) (23%) subgroups by new classification. No patient was classified for sclerotic subgroup. Median e-GFR values for the histopathologic subgroups during the follow-up visits were shown in figure 1. The focal subgroup demonstrated stable e-GFR values during the follow-up with the highest median e-GFR values in comparison to the other subgroups. Initial e-GFR<15 was found as 53% in the CS. e-GFR was found to be increased significantly between the initial and each follow-up visits in those patients. The MS had an increased e-GFR values, which was became significant 12th and 24th months visits, during the follow-up. Only CS showed a positive correlation between the percentage of the number of normal glomeruli and the e-GFR changes during the first 2 years, but it was not statistically significant.
Conclusions The focal category according to the new histopathological classification was found to have a better renal outcome in this small group of AAV nephritis cohort, as reported in the literature. Three-forth of the patients, who underwent hemodialysis at the time of diagnosis were in the CS. A significant increase of e-GFR was demonstrated with the standard immunosuppressive treatment in the active patients. Renal function showed a trend towards an increase in accordance with the percentage of the normal glomeruli in the CS.
Disclosure of Interest None declared