1Policlinic of Internal Medicine, Ludwig-Maximilians-University, Munich and 2Department of Internal Medicine, Division of Nephrology, University of Erlangen-Nürnberg, Germany
Correspondence and offprint requests to: Sven Weidner, MD, Medizinische Poliklinik, Klinikum der Universität München-Innenstadt, Pettenkoferstrasse 8a, D-80336 München, Germany. Email: sweidner{at}med.uni-muenchen.de
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Abstract |
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Methods. In this retrospective analysis, 80 patients with a new diagnosis of WG, MPA or RLV with biopsy-proven renal involvement were followed over a median of 46.7 months (range: 0.8181.9 months). All patients had induction treatment with cyclophosphamide and oral corticosteroids.
Results. At the end of follow-up, 23% were dependent on dialysis. Renal survival was significantly worse in patients with WG compared with patients with MPA or RLV (P = 0.04). A higher rate of end-stage renal disease (ESRD) was noticed in PR3-ANCA- vs MPO-ANCA-positive patients. A total of 21 patients (26%) died. Predictors of patient mortality were development of ESRD, older age and the maximum creatinine in the first month. Mortality was found to be higher in patients with WG and was significantly higher in PR3-ANCA-positive cases (P = 0.02). The relative risk of death was 9.32 times higher in PR3-ANCA- vs MPO-ANCA-positive patients.
Conclusions. Our data underscore the pathogenetic potential of ANCA by demonstrating a more aggressive disease state and a poorer outcome in patients with PR3-ANCA.
Keywords: anti-neutrophil cytoplasmic antibody; microscopic polyangiitis; outcome; vasculitis; Wegener's granulomatosis
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Introduction |
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Renal involvement is frequent in ANCA-associated vasculitis and was shown to be one of the negative prognostic factors of mortality [24]. Besides full-blown systemic vasculitis with renal involvement, its renal-limited variant is characterized by the absence of vasculitis in any other organ. This renal-limited vasculitis (RLV), previously named idiopathic necrotizing crescentic glomerulonephritis, is now widely accepted to form an entity within the ANCA-associated vasculitides and may be regarded as a forme-fruste [5]. The differences in patient survival and renal outcome between RLV, MPA and WG have not been analysed in detail.
Several studies have described clinical features, performed outcome analysis and attempted to determine prognostic markers in ANCA-associated vasculitis with renal involvement [3,611]. However, many of these studies have assessed only small patient numbers or performed analysis for one disease (WG or MPA) only.
In this study, we analysed the outcome in a large cohort of ANCA-associated vasculitis treated with cyclophosphamide and oral corticosteroids for remission induction. All patients had biopsy-proven renal involvement. Attention was especially focused on patient and renal survival in the diagnostic subgroups and the influence of ANCA antigen specificity on these parameters.
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Subjects and methods |
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Patient classification
According to the proposal of the CHCC [12], patients were retrospectively divided into the following diagnostic subgroups.
Wegener's granulomatosis
Patients with systemic vasculitis and presence of granulomatous inflammation in biopsy specimen or presence of clinical signs strongly suggestive for granulomatous disease. This comprised involvement of the upper respiratory tract with nasal inflammation (purulent/bloody nasal discharge), sinusitis or otitis media or lower respiratory tract manifestation with pulmonary nodules or fixed infiltrates.
Microscopic polyangiitis
Patients with systemic vasculitis and absence of granuloma formation in biopsy specimen and absence of clinical signs strongly suggestive for granulomatous disease.
Renal-limited vasculitis
Patients with biopsy-proven pauci-immune necrotizing glomerulonephritis without symptoms of systemic vasculitis.
According to the CHCC, non-invasive evaluations could be used to identify abnormalities that adequately predicted the presence of granulomatous inflammation without having to perform a histological examination. As required by this nomenclature, ANCA antigen specificity was not used as a definition criterion.
Data collection
Start and endpoint
Patients were entered into the study from the time point when renal biopsy was performed and a diagnosis of ANCA-associated vasculitis was established. All data were retrospectively registered at diagnosis and during follow-up by systematically reviewing medical records on patients history, laboratory analysis and medication. Glomerular filtration rate (GFR) was calculated using the equation by Cockcroft and Gault [13]. Patients were followed until a given endpoint (end of data collection), end-stage renal disease (ESRD) or death occurred.
ANCA analysis
All patients had been tested for the presence of ANCA by indirect immunofluorescence (iIF) as well as for PR3-ANCA and MPO-ANCA by enzyme-linked immunosorbent assay (ELISA). The iIF tests and ELISA systems used for ANCA detection were manufactured by Euroimmun (Lübeck, Germany).
Organ involvement
Organ manifestations were only registered if symptoms could be ascribed to active vasculitis or objective assessment confirmed the clinical presentation to be attributable to vasculitis. The disease extent index (DEI) was used as a parameter to assess the degree of organ involvement [14].
Treatment
All patients received a homogeneous induction treatment according to local treatment guidelines. None of the patients had received any immunosuppressive medication before diagnosis. All patients received induction treatment with cyclophosphamide (CYC; 2 mg/kg body weight) and oral corticosteroids (OCS; 1 mg/kg body weight). A CYC dose reduction by 25% was performed for age >65 years and for GFR <50 ml/min. A dose reduction by 50% was performed for GFR <10 ml/min. In 50 patients, treatment with OCS was preceded by intravenous pulse methylprednisolone (MEP) (mean: 4.3 mg/kg body weight; range: 2.315.1 mg/kg body weight) for 3 consecutive days. Plasmapheresis was additionally used in five patients. In 16 patients, CYC was switched to azathioprine (AZA) after reaching stable remission (median: 6 months; range: 4.213 months). Five patients had been included in the European Vasculitis Study Group (EUVAS) CYCAZAREM trial and three patients were studied in MEPEX.
Treatment response
Remission
Remission was defined as the stabilization or improvement of renal function and resolution of extrarenal manifestations of systemic vasculitis. The status of complete remission was supported by normalization of laboratory parameters (erythrocyte sedimentation rate, C-reactive protein and leukocyte count).
Relapse
Relapse was defined as a rise in creatinine concentration occurring with a nephritic sediment or worsening/new extrarenal manifestation involving the typical organ systems. Symptoms were only registered as relapse if they could be ascribed to active vasculitis or objective assessment confirmed the clinical presentation to be attributable to vasculitis.
Statistical analysis
Statistical analysis was performed with SPSS 11.0 for windows (SPSS Inc., Chicago, IL, USA). Medians and ranges are reported for non-normal distributed data and means±SD are reported for normal-distributed data. Differences between means were tested using the Student's t-test. The MannWhitney U-test was applied for non-parametric comparison of metric data. The 2-test was used for comparison of categorical data. KaplanMeier life-table analysis was used to assess patient survival, renal survival and relapse-free survival. Relapse-free survival was only determined in patients living long enough to experience relapse. Pearson's correlation coefficients were calculated to determine an association between relapse-free survival and the duration of initial therapy. Univariate survival analysis was performed using the log-rank test. Multivariate analysis of patient survival used Cox's regression model. Variables that did not affect survival significantly were removed by a backwards stepwise procedure according to a likelihood ratio. All tests were two-tailed and P-values of <0.05 were considered significant.
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Results |
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All patients were tested for ANCA by iIF and ELISA. Seventy-six (95%) patients had a positive test result. By ELISA, PR3-ANCA or MPO-ANCA were found in 74 (92.5%) patients. Table 2 shows the frequency of PR3-ANCA and MPO-ANCA in association with diagnostic subgroups.
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Follow-up
The median duration of follow-up was 46.7 months with a range of 0.8181.9 months.
Treatment
At the start of treatment, CYC was given at a mean daily dose of 1.7 mg/kg body weight. The duration of cytotoxic treatment (CYC and AZA) during induction treatment and the following period of stable remission was analysed from the time of diagnosis until the drug was completely withdrawn for the first time (further called initial cytotoxic treatment). Temporary interruptions of immunosuppression (in the case of infection, leukopenia, etc.) were not regarded as discontinuation, if cytotoxic therapy was resumed. Patients who were still on induction treatment at the end of data collection or who had died during active disease were excluded from the analysis of initial cytotoxic treatment (n = 18). In the whole group, the median time of initial cytotoxic treatment was 18 months (range: 0.595 months).
OCS were initially given for a median duration of 33 months (range: 1.667 months). In 50 patients, treatment with OCS was preceded by pulse MEP. These patients presented with significantly higher creatinine levels (median: 528 vs 380 µmol/l; P = 0.02) and lower GFR. Patients having received MEP were evenly distributed between WG and MPA, while only a minority of RLV had been treated with MEP. No difference in renal and patient survival was observed regarding pulse MEP (data not shown).
Treatment response
Remission. Complete remission could be achieved in 72 patients (90%). The remaining eight patients died while suffering from active vasculitis.
Relapses
A total of 46 relapses occurred in 26 patients (33%). Twelve patients experienced more than one relapse and three patients had four relapses. The first relapse (n = 26) occurred after a median time of 17.2 months (range: 2111 months). No significant differences in relapse rate were found according to ANCA or diagnostic subgroups.
At the time of the first relapse, 12 patients (of 26; 46%) had ongoing CYC/AZA treatment and 15 received OCS (58%). In patients without treatment at relapse, relapse-free survival correlated highly significantly with the duration of initial cytotoxic treatment. The longer the treatment had been administered, the longer relapse-free survival was observed in these patients (CYC/AZA: r = 0.91, P<0.001; OCS: r = 0.88, P<0.001).
Renal survival
After 1 month of treatment the creatinine had fallen to a median of 194 µmol/l with a further reduction to 140 µmol/l after 1 year. At the end of follow-up, 18 patients (23%) suffered from ESRD. ESRD occurred in a median time of 1.9 months (range: 0129.6 months). Eight of the 22 patients (36%) requiring dialysis at the time of diagnosis remained at ESRD. Plasmapheresis was additionally used in five patients, which were all PR3-ANCA-positive and had WG. Only one of these patients progressed to ESRD.
For analysis of renal survival according to initial creatinine, patients were divided into three groups of equal size. Patients presenting with high creatinine levels (>582 µmol/l) progressed significantly more frequently to ESRD than patients with low serum creatinine (299 µmol/l) (P<0.001; data not shown). Figure 1A shows the assessment of renal survival according to diagnostic subgroups. Progression to ESRD occurred significantly more often in patients with WG (n = 11), while only six patients with MPA and one with RLV progressed to ESRD (P = 0.04). Figure 1B shows the analysis of renal survival according to ANCA antigen specificity: 12 patients with PR3-ANCA and six patients with MPO-ANCA developed ESRD (P = 0.26, not significant).
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No statistical difference was seen according to diagnostic subgroups; however, patients with WG showed a higher tendency to die: nine of 32 patients with WG (28%) died vs five of 28 patients with MPA (18%), while three deaths (15%) were recorded in patients with RLV (P = 0.29). Figure 2A shows the assessment of patient survival according to diagnostic subgroups. By intention-to-treat analysis (not censoring cases, in which the cause of death was unrelated to vasculitis), mortality rates were identical to the statistical analysis with censored cases: 17 PR3-ANCA- and four MPO-ANCA-positive patients died (P = 0.012) and 11 with WG died vs seven with MPA. There were three deaths in patients with RLV (P = 0.29).
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Mortality was significantly higher in patients requiring dialysis at diagnosis, with 10 of 22 vs 11 of 58 without renal replacement therapy (P = 0.023). At the end of follow-up, 11 of the 18 patients suffering from ESRD had died. The 1 and 5 year patient survival rates were 83% and 61% for patients with ESRD and 87% and 87% for patients with preserved renal function, respectively. Comparison of survival curves showed a significantly worse survival for patients with ESRD (P = 0.029; Figure 3A). By univariate analysis, the relative risk of death was 3.06 times higher in patients with ESRD compared with patients with preserved renal function.
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Prognostic factors of patient survival
Cox's regression model was used for multivariate analysis of selected variables as prognostic factors of patient survival, controlling for diagnostic subgroup, ANCA subspecificity, age, DEI, pulmonary- or upper respiratory tract involvement and the maximum creatinine or minimum creatinine clearance in the first month. Variables that had already shown significantly higher mortality by univariate analysis proved to be significant prognostic factors with Cox's model thus predicting patient survival at diagnosis (Table 4).
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Age and the maximum creatinine were further used as metric variables in the Cox's regression model. The higher the age, the higher the risk of death: a 1.082-fold increase in risk per year of age was noted, corresponding to a doubling in risk of death every 8.8 years. Likewise, for the maximum creatinine, a 1.003-fold increase in risk per µmol/l creatinine was observed. A doubling in risk of death could be calculated from these data in steps of 277 µmol/l creatinine.
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Discussion |
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Our data regarding demographic characteristics, organ involvement and ANCA analysis correspond well to the findings of other investigators [811]. ANCA-associated vasculitis is a relapsing disease. In the present study, a relapse rate of 33% was noted, with the majority of patients relapsing after 2 years. Other studies have reported similar relapse rates of 1146% in cohorts of WG and MPA or MPA and RLV [11,15]. There was a trend towards higher relapses in patients with PR3-ANCA compared with MPO-ANCA-positive patients, which did not reach statistical significance (47% vs 35%). The relapse rate in patients with WG was only slightly higher compared with MPA (46 vs 42%, not significant). This differs from the prospective CYCAZAREM study, where patients with WG had a greater chance of relapse than in MPA. The data from CYCAZAREM, however, support the notion of an eventually more aggressive disease state in WG, possibly due to the presence of granulomatous disease and the colonization of diseased respiratory mucosa with Staphylococcus aureus [16].
As immunosuppressive treatment should control disease activity, relapses may be expected to occur when treatment is tapered or has been discontinued. In a study by Aasarød et al. [6], more patients with relapses were not receiving cytotoxic agents, while in an analysis by Westman et al. [11], the majority (69%) had ongoing treatment. Gordon et al. [15] noticed slightly more relapses (57%) under therapy. In general, the discontinuation of cytotoxic drugs has been proposed to promote higher relapse rates [15]. In this study, 50% were still on immunosuppressive treatment at the time of relapse. In patients without treatment at relapse, relapse-free survival was significantly influenced by the duration of initial cytotoxic treatment. The longer the treatment was administered, the longer overall relapse-free survival was observed in these patients. Whether immunosuppressive treatment may be safely discontinued after a defined period of remission will be answered by REMAIN, one of the trials performed by EUVAS.
Regarding outcome in patients with ANCA-associated vasculitis, the most important questions focus on whether there are differences in mortality and renal survival between the disease entities WG, MPA and RLV and whether there are differences between patients with MPO-ANCA and those with PR3-ANCA.
According to our data, organ involvement and the development of ESRD as well as mortality seem to be influenced by the underlying disease and the ANCA antigen specificity. In this analysis, PR3-ANCA-positive patients had more organs affected at diagnosis than patients with MPO-ANCA, which has been confirmed by other studies [11,17,18]. Progression to ESRD occurred significantly more often in patients with WG (n = 11) compared to patients with MPA (six patients; P = 0.04) and RLV (one patient; P = 0.021). Renal survival was worse in PR3-ANCA-positive patients (not significant). Similarly, patients with WG had a higher mortality than other patients. Furthermore, mortality was significantly higher in PR3-ANCA-positive cases, while none of the ANCA-negative patients died. The relative risk of death was 9.32 times higher in PR3-ANCA-positive patients compared with MPO-ANCA. In contrast, RLV and ANCA negativity were shown to be relatively benign conditions with rather good outcomes concerning death and ESRD. MPA and positivity for MPO-ANCA could be demonstrated to follow a course between WG and RLV or PR3-ANCA and ANCA negativity, respectively. Further prognostic factors associated with significantly higher mortality were older age, ESRD and high maximum creatinine in the first month.
Plasmapheresis was additionally used in five patients, which were all PR3-ANCA-positive and had WG. Only one of these patients progressed to ESRD. These data are in accordance with MEPEX, one of the trials performed by EUVAS, where the major result was the improvement of renal survival by plasmapheresis [19]. No influence of plasmapheresis on renal survival analysis in this study can be determined, as none of the patients with MPO-ANCA or MPA received plasma exchange.
Some studies have demonstrated an influence of PR3-ANCA on disease manifestation or outcome; however, no impact of ANCA subspecificity on mortality has been observed [20]. A higher relapse rate has been seen in PR3-ANCA [17,18] and a higher risk of death has been noted in C-ANCA-positive patients [9]. In an excellent study by Westman et al. [11], no difference regarding mortality was registered according to ANCA subspecificity; however, for the first time, the data presented in their study demonstrated a relationship between PR3-ANCA levels and outcome in ANCA-associated vasculitis. High levels measured by the sensitive capture ELISA at diagnosis were of significant prognostic value of renal survival and a tendency for higher mortality was shown.
We believe that the aggressiveness of WG is due to its high association with PR3-ANCA, and most probably patients with MPA who are positive for PR3-ANCA have a similar disease activity and outcome. In the study by Hogan et al. [9], where patients with WG had been strictly excluded and only patients with necrotizing crescentic glomerulonephritis or MPA were analysed, the relative risk of death was 3.78 times greater in the presence of a C-ANCA pattern that is almost exclusively associated with PR3-ANCA.
Our data underscore the pathogenetic potential of ANCA, where a more aggressive disease state and a poorer outcome can be attributed to the presence of PR3-ANCA. Although these data consist of a retrospective analysis, the strength of this study is that all patients had biopsy-proven renal involvement and induction treatment with CYC and OCS. Outcome analysis of renal and patient survival was not based on the comparison of events between subgroups, but was calculated from KaplanMeier life-table analysis. The determination of prognostic factors for patient survival using Cox's regression model provides important and reliable information for risk stratification. However, ANCA-associated vasculitis is a rare disease. To avoid the statistical difficulties inherent in retrospective studies with small patient numbers, large prospective trials are necessary to allow reliable outcome analysis. An approach could be the long-term follow-up of the multicentre activities of EUVAS, where a large collective is treated uniformly with standardized immunosuppression in consecutive trials.
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Acknowledgments |
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Conflict of interest statement. None declared.
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References |
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