
==== Front
Ren Fail
Ren Fail
Renal Failure
0886-022X
1525-6049
Taylor & Francis

39258391
10.1080/0886022X.2024.2400539
2400539
Version of Record
Research Article
Glomerulonephritis and Immunologic Disorders
Plasmapheresis, immunosuppressive therapy and anti-GBM disease prognosis: a cohort study of 107 patients
Y. Liu et al.
Liu Ying ab†
Wu Yiting ab†
Wei Wei ab†
Yang Letian ab
Liu Caihong ab
Li Jian ab
Huang Yongxiu ab
Wang Bo ab
Yang Yingying ab
Zhang Ling ab
Fu Ping ab
Zhao Yuliang ab
a Department of Nephrology, West China Hospital, Sichuan University, Chengdu, China
b Kidney Research Institute, West China Hospital, Sichuan University, Chengdu, China
† These authors contributed equally to this work.

Supplemental data for this article can be accessed online at https://doi.org/10.1080/0886022X.2024.2400539.

CONTACT Yuliang Zhao zhaoyuliang@scu.edu.cn Department of Nephrology, West China Hospital, Sichuan University, No.37, Guoxue Alley, Chengdu, Sichuan Province 610041, China.
11 9 2024
2024
11 9 2024
46 2 240053930 4 2024
4 8 2024
30 8 2024
KnowledgeWorks Global Ltd.10 9 2024
published online in a building issue10 9 2024
© 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group
2024
The Author(s)
https://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.

Abstract

Background

Anti-glomerular basement membrane (anti-GBM) disease presents with rapidly progressive glomerulonephritis and alveolar hemorrhage, requiring urgent management. In this study, we analyzed the relationship between plasmapheresis strategy, immunosuppressive therapy and the prognosis of anti-GBM disease patients.

Method

We screened newly diagnosed anti-GBM disease patients at West China Hospital of Sichuan University from 2010 to 2021. The primary outcome was a composite endpoint of in-hospital death or dialysis dependency upon discharge.

Results

This study enrolled 107 anti-GBM disease patients. The use of plasmapheresis was independently associated with a reduced risk of primary outcome (OR: 0.179, 95% Cl: 0.051–0.630, p = 0.007), better 2-year (HR: 0.146; 95% CI: 0.038–0.553; p = 0.005) and 8-year patient survival (HR: 0.309; 95% CI: 0.112–0.850; p = 0.023). Restricted cubic spline regression suggested that patients with 5–10 sessions of plasmapheresis had already achieved maximum risk reduction in the primary outcome. Patients who started plasmapheresis at lower serum creatinine (42.9% vs. 96.2%, p < 0.001) or lower anti-GBM antibody levels (44.4% vs. 93.3%, p = 0.030) had lower risk of primary outcome than those at higher levels. Use of high-dose methylprednisolone (p = 0.505), pulsed cyclophosphamide (p = 0.343) or ANCA positivity (p = 0.115) were not related to primary outcome in anti-GBM disease.

Conclusion

Plasmapheresis was protective for both in-hospital outcome and long-term survival in anti-GBM disease. Patients who initiated plasmapheresis early had a better prognosis and might only need 5–10 plasmapheresis sessions to achieve maximal risk reduction. Use of high-dose methylprednisolone or cyclophosphamide pulses was not related to improved short- or long-term outcomes in anti-GBM disease.

Keywords

Anti-GBM disease
plasmapheresis
immunosuppressive therapy
prognosis
the Science and Technology Department of Sichuan Province 24GJHZ0169 the National Key Research and Development Program of China 2023YFC2411800 135 project for disciplines of excellence, West China Hospital, Sichuan University 2020HXFH014 This study was supported by the Science and Technology Department of Sichuan Province (2024YFHZ0329), the National Key Research and Development Program of China (2023YFC2411800) and 135 project for disciplines of excellence, West China Hospital, Sichuan University (2020HXFH014). The funding sources had no involvement in this study.
==== Body
pmc1. Introduction

Anti-glomerular basement membrane (anti-GBM) disease is a kind of small vessel vasculitis that presents with proliferative glomerulonephritis, pulmonary hemorrhage or both. Anti-GBM disease patients produce IgG autoantibodies to the α-3-chain of type IV collagen, which facilitates the activation of the classical complement pathway inducing neutrophil-mediated inflammation and incites glomerular crescent formation in up to 95% of patients [1,2]. Timely removal of circulating antibodies is key to successful treatment, along with immunosuppressive therapy to further inhibit autoantibody production. Since the inclusion of plasmapheresis, there has been substantial improvement in disease prognosis [3,4]. In a large cohort study of 221 patients, the combined therapy of plasmapheresis plus corticosteroids and cyclophosphamide (CTX) had an overall beneficial effect on both patient and renal survival [5]. The American Society for Apheresis (ASAP) guidelines recommend plasmapheresis as the first-line treatment, with a minimum course of 10–20 days [6]. However, some technical details remain unanswered in the treatment of anti-GBM disease, such as whether patients will also benefit from plasmapheresis below the recommended number of sessions? When should plasmapheresis be provided? Should high-dose methylprednisolone (MP) or pulsed CTX be considered as routines? In this study, we retrospectively enrolled anti-GBM disease patients in a university-affiliated tertiary hospital from 2010 to 2021 and analyzed the relationship between plasmapheresis, immunosuppressive therapy and other risk factors and the prognosis of anti-GBM disease patients.

2. Methods

2.1. Patient selection

We screened and reviewed the medical records at West China Hospital of Sichuan University from 2010 to 2021. The patients were recruited based on the following inclusion criteria: i) positive for serum anti-GBM antibody (above 20 U/L) and ii) presented with rapidly progressive glomerulonephritis with/without pulmonary hemorrhage. The exclusion criteria were as follows: i) complicated with other potential causes of GBM disorder and crescentic nephritis, such as Alport syndrome, membranous nephropathy, IgA nephropathy, TTP or SLE etc.; ii) patients who had already received dialysis or plasmapheresis at a referring hospital before the present admission; and iii) insufficient follow-up data for analysis.

The study was approved by the Institutional Review Board of West China Hospital of Sichuan University (Approval No. of the ethics committee: 2021-1141) and abided by the Declaration of Helsinki. Specific identifiers of protected individual health information, such as names, geographic subdivisions and medical record numbers, were removed from the data set during data analysis. Patient informed consent was waived, as this was a retrospective study.

2.2. Treatment protocol

As this was a retrospective study, the therapeutic regime was at the discretion of the attending physician. In principle, diagnosed anti-GBM disease patients or suspected cases with pending anti-GBM antibody serology were promptly treated with corticosteroids and plasmapheresis. The patients might escalate to combined corticosteroids and CTX after assessment for risk and benefit. However, dialysis-dependent or advanced renal failure (100% crescents or >50% global glomerulosclerosis in an adequate biopsy sample) patients without pulmonary hemorrhage might consider conservative approach. By performing plasmapheresis, we aimed to achieve serum-negativity of anti-GBM antibody with serial titer measurement and resolution of active glomerular/pulmonary injury, or until when plasmapheresis is no longer indicated, such as when a renal biopsy returns showing a very high degree of glomerulosclerosis in a patient without alveolar bleeding.

2.3. Data collection

Demographic data, laboratory results, use of immunosuppressives, renal replacement therapy and plasmapheresis were extracted from the electronic health records (EHRs) flowsheet. Comorbidities were determined by ICD-9/10-CM codes. The laboratory parameters, including anti-GBM antibody, eGFR, neutrophil (Neu) count, lymphocyte (Lym) count, platelet (PLT) count, hemoglobin (Hb) level, blood urea nitrogen (BUN) level, creatinine (Scr) level, albumin (ALB) level, total protein (TP) level, and total bilirubin (TBIL) level, were collected on the first or second day of hospitalization. Follow-up data were collected by searching medical records and telephone calls.

2.4. Clinical outcomes

The clinical outcomes include outcomes during hospitalization and long-term follow-up outcomes. The primary outcome during hospitalization was a composite endpoint of in-hospital death or dialysis dependency upon discharge. Two-year mortality and 8-year mortality were also analyzed.

2.5. Statistical analyses

Continuous variables are expressed as the mean ± SD or median (range) and were compared between groups using the t test or Wilcoxon test. Categorical variables are expressed as numbers and percentages and were assessed with the chi-squared test or Fisher’s exact test, while the Bonferroni method was used for comparisons among three or more groups. Logistics regression and restricted cubic spline regression analyses were used to evaluate the risk of the primary outcome. Restricted cubic spline regression is model to observe the non-linear relationships between continuous variables (number of plasmapheresis sessions) and outcomes (primary outcome). In this study, knots were placed at 5th, 35th, 65th, and 95th percentiles for the spline regression. Kaplan–Meier curves and Cox proportional hazards regression were used for long-term survival analysis. The results are expressed as odds ratio (ORs) and hazard ratios (HRs) with 95% coincidence intervals (95% CIs). Crude risk factors which are of statistical significance (p < 0.05) were included into the multivariate analysis. To avoid over adjustment, closely relevant variates (such as eGFR and serum creatinine) were not repeated included. All statistical analyses were performed using IBM SPSS software (version 26.0; IBM Corp., Armonk, NY, USA) and R (version 4.1.1; R Foundation for Statistical Computing, Vienna, Austria). Statistical significance was defined as a two-tailed p < 0.05.

3. Results

3.1. Patient characteristics

This study enrolled 107 anti-GBM disease patients, of whom 59 were females (55.1%) with a mean age of 49 ± 18 years (Table 1). Note that the patients had a bimodal distribution in age, with 2 peaks at approximately 25 years and 60 years (Figure 1(A)). The mean serum creatinine at admission was 673.73 ± 392.56 μmol/L. The mean circulating anti-GBM antibody level was 126.77 ± 102.79 u/L. During hospitalization, 32 patients (29.9%) suffered hemoptysis, while 86 patients (80.4%) required renal replacement therapy (RRT). All 107 patients received immunosuppressive therapy with corticosteroids and/or CTX. Thirty-six patients (33.6%) received high-dose intravenous MP (>500 mg/d), 26 (24.3%) received pulsed-intravenous CTX, and 16 (15.0%) patients received both. Sixty patients (56.1%) received at least one session of plasmapheresis with a median number of five sessions (range from 1 to 22 sessions). The distribution of patients by the number of plasmapheresis is shown in Figure 1(B). There were 47 patients who did not receive plasmapheresis, including 30 patient who were unlikely to benefit from plasmapheresis basing on KDIGO guidelines (dialysis-dependent, or 100% crescents, or >50% global glomerulosclerosis, no pulmonary hemorrhage) [7] and 13 patients who refused the treatment due to finance and other reasons. There were no significant differences in demographics, clinical features and most laboratory parameters between patients who received plasmapheresis and who did not (Table 1). The characteristics of the study population at presentation by baseline renal function were shown in Supplementary Table 1.

Figure 1. Patient distribution by age and number of plasmapheresis sessions. (A) The distribution of patients by age. (B) The distribution of patients by the number of plasmaspheres.

Table 1. Characteristics of the study population at presentation.

 	Overall (N = 107)	Plasmapheresis (−) (N = 47)	Plasmapheresis (+) (N = 60)	P value	
Characteristics	 	 	 	
Female	59 (55.1%)	25 (53.2%)	23 (38.3%)	0.181	
Age, year	49 (18)	52.15 (17.64)	47.22 (17.83)	0.157	
Clinical features	 	 	 	
Pneumonia	47 (43.9%)	17 (36.2%)	30 (50%)	0.217	
Hemoptysis	32 (29.9%)	14 (29.8%)	18 (30%)	1.000	
Diabetes	5 (4.7%)	2 (4.3%)	3 (5%)	1.000	
Hypertension	46 (43.9%)	22 (46.8%)	24 (40%)	0.611	
Serology	 	 	 	
Anti-GBM antibody level, u/L	126.77 (102.79)	120.91 (106.29)	131.35 (100.62)	0.604	
ANCA and Anti-GBM positive	24 (22.4%)	11 (23.4)	13 (21.7)	1.000	
eGFR, ml/min(range)	15.33 (24.03)	17.03 (29.04)	13.99 (19.38)	0.519	
Serum creatinine, μmol/L	673.73 (392.56)	726.05 (423.37)	632.75 (365.01)	0.224	
Urea, mg/dL	19.71 (10.39)	20.7 (10.06)	18.88 (10.68)	0.378	
Total protein, mg/dL	60.85 (7.98)	61.02 (8.7)	60.70 (7.36)	0.847	
Albumin, mg/dL	31.25 (5.60)	30.68 (5.53)	31.76 (5.67)	0.342	
Globin, mg/dL	29.61 (7.36)	30.34 (7.97)	28.94 (6.77)	0.351	
Alanine transaminase, (IU/L)	20.24 (18.81)	22.09 (22.38)	18.57 (14.92)	0.360	
Aspartate transaminase, (IU/L)	24.58 (23.72)	30.17 (31.14)	19.53 (12.34)	0.027	
Red blood cell count,109/L	2.87 (0.64)	2.77 (0.65)	2.96 (0.62)	0.151	
Hemoglobin, g/L	81.8 (19.26)	79.39 (19.2)	83.79 (19.25)	0.254	
White blood cell count,109/L	9.65 (4.36)	8.95 (3.69)	10.23 (4.8)	0.142	
Absolute neutrophil count, 109/L	8.59 (8.58)	7.17 (3.38)	9.76 (11.07)	0.134	
Granulocyte, 109/L	78.94 (11.84)	80.26 (8.6)	77.86 (13.95)	0.311	
Lymphocyte, 109/L	1.08 (0.59)	0.98 (0.62)	1.16 (0.56)	0.130	
Platelet count, 109/L	224.84 (140.21)	222.6 (175.79)	226.68 (103.96)	0.885	
Treatment	 	 	 	
Plasmapheresis	60 (56.1%)	/	/	/	
Plasmapheresis sessions	5 (1–22)	/	/	/	
Pulsed CTX	26 (24.3%)	8 (17%)	18 (30%)	0.185	
High-dose MP	36 (33.6%)	5 (10.6%)	31 (51.7%)	0.000	
Renal replacement therapy	86 (80.4%)	35 (74.5%)	51 (85%)	0.264	
Outcomes	 	 	 	
Primary outcome	70 (65.4%)	36 (76.6%)	34 (56.7%)	0.034	
Two-year patient survivala	30 (46.2%)	13 (44.8%)	17 (47.2%)	1.000	
Eight-year patient survivala	6 (9.2%)	3 (10.3%)	3 (8.3%)	1.000	
eGFR: estimated glomerular filtration rate; Anti-GBM: Anti-glomerular basement membrane; ANCA: Antineutrophil cytoplasmic antibody; MP: Methylprednisolone; CTX: Cyclophosphamide.

aAvailable in 65 subjects.

Data are presented as numbers (%), means ± SD, or medians (range).

There were 24 (22.4%) patients who were also positive for anti-neutrophil cytoplasmic antibody (ANCA) (Table 1). Double-positive patients had higher serum creatinine at hospital admission (833.83 vs. 627.44 μmol/L, p = 0.028) and were more likely to receive pulsed CTX (p = 0.028), rather than high-dose MP (p = 0.347) or plasmapheresis (p = 0.831).

3.2. Risk factors for the primary outcome

There were 22 in-hospital deaths, and 48 patients were dialysis-dependent upon discharge. A total of 70 patients (65.4%) hence reached the primary outcome. Univariate analysis (Table 2) suggested that baseline anti-GBM antibody level (p = 0.033), eGFR (p = 0.004), serum creatinine (p < 0.001), BUN (p = 0.003), red blood cell count (0.016), total protein (p = 0.035), albumin (p = 0.001), pneumonia (p = 0.034), and not using plasmapheresis (p = 0.034) were potential risk factors for primary outcome, rather than age (p = 0.516), sex (p = 0.514), hypertension (p = 0.770), diabetes (p = 0.828), hemoptysis (p = 0.076), ANCA positivity (p = 0.115), use of high-dose MP (p = 0.505) or pulsed CTX (p = 0.343). In the multivariate logistic regression (Table 2) adjusted for the aforementioned crude risk factors, the use of plasmapheresis was independently associated with a reduced risk of the primary outcome (OR: 0.179, 95% Cl: 0.051–0.630, p = 0.007), while a higher eGFR at admission also predicted a decreased risk (p = 0.039). In patients who received plasmapheresis, the additional use of high-dose MP/pulsed CTX did not bring further improvement in the risk of the primary outcome (p = 0.138) (Figure 2(A)).

Figure 2. The incidences of the primary outcome for different patient groups. (A) The incidences of the primary outcome for patients with/without high-dose MP/pulsed CTX and with/without plasmapheresis. (B) The incidences of the primary outcome for patients with low/high antibody levels (−/+) and with/without plasmapheresis. (C) The incidences of the primary outcome for patients with low/high Scr (−/+) and with/without plasmapheresis. MP: methylprednisolone, CTX: cyclophosphamide.

Table 2. Univariable and multivariable risk factor analysis for primary outcome.

Variables	Univariable analysis	Multivariable analysis	
OR	95%Cl	P value	OR	95%Cl	P value	
Age	0.993	0.970–1.015	0.516	 	 	 	
Sex	0.764	0.341–1.713	0.514	 	 	 	
Anti-GBM antibody	1.006	1.000–1.011	0.033	1.006	0.999–1.014	0.107	
eGFR	0.941	0.903–0.980	0.004	0.951	0.906–0.998	0.039	
Serum creatinine	1.003	1.001–1.004	<0.001	 	 	 	
ANCA and Anti-GBM positive	2.384	0.810–7.019	0.115	 	 	 	
Pneumonia	2.503	1.073–5.835	0.034	2.345	0.728–7.549	0.153	
Diabetes	0.731	0.043–12.436	0.828	 	 	 	
Hypertension	0.840	0.261–2.703	0.770	 	 	 	
Hemoptysis	2.381	0.914–6.200	0.076	 	 	 	
Plasmapheresis	0.400	0.171–0.932	0.034	0.179	0.051–0.630	0.007	
High-dose MP	0.753	0.327–1.734	0.505	 	 	 	
Pulsed CTX	0.645	0.260–1.597	0.343	 	 	 	
High-dose MP/Pulsed CTX	0.704	0.315–1.570	0.391	 	 	 	
Red blood cell count	0.430	0.217–0.854	0.016	0.786	0.297–2.081	0.628	
Hemoglobin	0.982	0.961–1.003	0.098	 	 	 	
White blood cell count	1.002	0.912–1.100	0.971	 	 	 	
Granulocyte	1.009	0.976–1.044	0.585	 	 	 	
Absolute neutrophil count	1.020	0.954–1.113	0.450	 	 	 	
Lymphocyte	0.904	0.450–1.819	0.778	 	 	 	
Blood platelet count	1.001	0.998–1.004	0.675	 	 	 	
Prothrombin time	1.191	0.941–1.508	0.146	 	 	 	
International normalized ratio	6.473	0.444–94.401	0.172	 	 	 	
Activated partial thromboplastin time	1.050	0.983–1.120	0.145	 	 	 	
Fibrinogen determination	1.179	0.912–1.523	0.208	 	 	 	
Fibrinogen degradation product	1.014	0.967–1.064	0.556	 	 	 	
D-Dimer	1.060	0.972–1.156	0.188	 	 	 	
Total bilirubin	0.929	0.829–1.042	0.209	 	 	 	
Direct bilirubin	1.034	0.819–1.303	0.781	 	 	 	
Alanine transaminase	1.004	0.981–1.028	0.734	 	 	 	
Aspartate transaminase	1.013	0.986–1.041	0.352	 	 	 	
Total protein	0.940	0.888–0.996	0.035	0.976	0.894–1.066	0.593	
Albumin	0.861	0.790–0.939	0.001	0.904	0.802–1.020	0.100	
Globin	1.012	0.956–1.072	0.678	 	 	 	
Urea	1.079	1.027–1.134	0.003	1.004	0.943–1.068	0.903	
Uric acid	1.002	0.999–1.006	0.142	 	 	 	
C-reactive protein	1. 000	0.976–1.024	0.969	 	 	 	
eGFR: estimated glomerular filtration rate; Anti-GBM: anti-glomerular basement membrane; ANCA: antineutrophil cytoplasmic antibody; MP: methylprednisolone; CTX: cyclophosphamide.

p < 0.05 was considerated as significant. Significant P values are represented in bold. Multivariable analysis is adjusted for anti-GBM antibody level, eGFR, pneumonia, plasmapheresis, red blood cell count, total protein, albumin and Urea.

3.3. Timing of plasmapheresis and patient prognosis

To investigate the influence of the baseline anti-GBM antibody level on the therapeutic effect of plasmapheresis, we classified patients into four groups by the median anti-GBM antibody level (108.49 U/L) and whether they received plasmapheresis, which showed a significant intergroup difference (p = 0.030). Patients who received plasmapheresis with a low anti-GBM antibody level (−) had the lowest risk of primary outcome (44.4%), while those with a high antibody level (+) without plasmapheresis had the highest (93.3%). Interestingly, patients with high antibody levels with plasmapheresis had a comparable incidence to those with low antibody levels without plasmapheresis (68.8%, 75.0%) (Figure 2(B)). Similarly, there was a significant intergroup difference (p < 0.001) when divided by plasmapheresis and median serum creatinine level (635.00μmol/L). Patients who initiated plasmapheresis at a lower serum creatinine level (−) showed the lowest incidence of primary outcome (42.9%), while patients with high creatinine levels (+) without plasmapheresis had the highest incidence (96.2%) (Figure 2(C)).

3.4. Number of plasmapheresis sessions and patient prognosis

Among the 107 patients, 60 (56.1%) received one or more sessions of plasmapheresis. We subsequently divided the patients into three groups: group A (no plasmapheresis, 47 patients), group B (1–5 plasmapheresis cycles, 31 patients) and group C (>5 plasmapheresis cycles, 29 patients). The incidences of the primary outcome were 76.6% (group A), 64.5% (group B) and 48.3% (group C), respectively, with a statistically significant difference (p = 0.041) (Figure 3(A)). Plasmapheresis seemed to be protective against the primary outcome regardless of the number of sessions performed (Figure 3(B)). Restricted cubic spline regression analysis showed a non-liner relation between number of plasmapheresis sessions performed and risk of primary outcome, which indicated that there was no additional incremental benefit for those who received more than 10 sessions of plasmapheresis, 5–10 sessions of plasmapheresis seemed to have achieved maximum risk reduction for the primary outcome (Figure 3(C)). Subgroup analysis confirmed the stability of the observed protective effect of plasmapheresis, irrespective of age, sex, pneumonia, hemoptysis, ANCA positivity, anti-GBM antibody, eGFR, high-dose MP and pulsed CTX (P interaction all >0.05) (Table 3).

Figure 3. Risk of primary outcome by number of plasmaphereses. (A) The incidences of the primary outcome for patients grouped by number of sessions of plasmapheresis. (B) Forest plots displaying risk of primary outcome by number of plasmaphereses. (C) Spline regression analysis on risk of primary outcome by number of plasmaphereses.

Table 3. Subgroup analysis of plasmapheresis on risk of primary outcome.

 	Primary outcome occurrence	Univariable analysis	 	
 	Plasmapheresis (+)	Plasmapheresis (−)	HR	95%Cl	P value	95%Cl	P for interaction	
Sex	 	 	 	 	 	0.053–1.740	0.181	
Male	52.20%	84.00%	0.208	0.054–0.799	0.022	 	 	
Female	59.50%	68.20%	0.684	0.225–2.080	0.504	 	 	
Age	 	 	 	 	 	0.237–7.1360	0.762	
<51.5	51.60%	76.20%	0.353	0.105–1.183	0.092	 	 	
>51.5	62.10%	76.90%	0.491	0.151–1.599	0.238	 	 	
Pneumonia	 	 	 	 	 	0.065–2.599	0.345	
Yes	73.30%	82.40%	0.589	0.133–2.606	0.486	 	 	
No	40.00%	73.30%	0.242	0.081–0.721	0.011	 	 	
Lung hemorrhage	 	 	 	 	 	0.268–36.118	0.365	
Yes	66.70%	92.90%	0.154	0.016–1.471	0.104	 	 	
No	52.40%	69.70%	0.478	0.183–1.247	0.131	 	 	
ANCA and Anti-GBM positive	 	 	 	 	 	0.153–24.734	0.609	
Yes	69.20%	90.90%	0.225	0.021–2.405	0.217	 	 	
No	53.20%	72.20%	0.437	0.173–1.105	0.080	 	 	
eGFR, ml/min (Range)	 	 	 	 	 	0.218–18.274	0.541	
<16.15	63.30%	84.60%	0.313	0.110–0.891	0.030	 	 	
>16.15	27.30%	37.50%	0.625	0.089–4.401	0.637	 	 	
Serum creatinine, umol/L	 	 	 	 	 	0.016–2.160	0.179	
<671.05	42.90%	52.40%	0.682	0.230–2.022	0.490	 	 	
>671.05	76.00%	96.20%	0.127	0.014–1.143	0.066	 	 	
Anti-GBM antibody (u/L)	 	 	 	 	 	0.090–4.390	0.639	
<44.705	26.70%	58.30%	0.227	0.046–1.125	0.069	 	 	
>44.705	66.70%	82.90%	0.429	0.146–1.259	0.123	 	 	
Pulsed CTX	 	 	 	 	 	0.164–10.652	0.792	
Yes	50.00%	75.00%	0.333	0.053–2.115	0.244	 	 	
No	59.50%	76.90%	0.441	0.168–1.160	0.097	 	 	
High-dose MP	 	 	 	 	 	0.089–13.810	0.935	
Yes	58.10%	80.00%	0.346	0.035–3.468	0.367	 	 	
No	55.20%	76.20%	0.385	0.139–1.066	0.066	 	 	
eGFR: estimated glomerular filtration rate; Anti-GBM: anti-glomerular basement membrane; ANCA: antineutrophil cytoplasmic antibody; MP: methylprednisolone; CTX: cyclophosphamide. (+): Patients with the treatment; (−): Patients without the treatment. Age, eGFR, serum creatine and anti-GBM level were classified by cutoff value suggested by AUC analysis.

3.5. Risk factors for long-term mortality

In Kaplan–Meier analysis, patients who received plasmapheresis had better 2-year (81.1% vs. 58.6%, p = 0.033) and 8-year survival (75.7% vs. 41.4%, p = 0.011) than those who did not (Figure 4(A and B)). In multivariate Cox regression analysis adjusted for rude risk factors, plasmapheresis was independently associated with better 2-year (HR: 0.146; 95% CI: 0.038–0.553; p = 0.005) and 8-year patient survival (HR: 0.309; 95% CI: 0.112–0.850; p = 0.023) (Tables 4 and 5). Clinical outcomes of patients with different baseline renal function by whether receiving plasmapheresis or not were shown in Supplementary Table 2. A higher blood granulocyte count at admission was also an independent risk factor for both 2-year (HR: 1.218; 95% CI: 1.071–1.385; p = 0.003) and 8-year mortality (HR: 1.112; 95% CI: 1.008–1.228; p = 0.034). High-dose MP/pulsed CTX seemed to be protective against 8-year mortality in Kaplan–Meier analysis (Figure 4(C and D)) but was not associated with long-term survival in Cox analysis (Tables 4 and 5). Relapse is rare in anti-GBM disease, occurring in 3% of patients [8]. In our cohort, we did not record any cases of remitting/relapsing disease during the follow-up.

Figure 4. Kaplan–Meier survival curves of plasmapheresis treatment and high-dose MP/pulsed CTX treatment. (A) Two-year patient survival curves by receiving plasmapheresis or not. (B) Eight-year patient survival curves by receiving plasmapheresis or not. (C) Two-year patient survival curves by receiving high-dose MP/pulsed CTX or not. (D) Eight-year patient survival curves by receiving high-dose MP/pulsed CTX or not. MP: methylprednisolone, CTX: cyclophosphamide.

Table 4. Univariable and multivariable cox analysis for 2-year survival.

Variables	Univariable analysis	Multivariable analysis	
HR	95%Cl	P value	HR	95%Cl	P value	
Age	1.021	0.995–1.048	0.120	 	 	 	
Sex	0.265	0.095–0.737	0.011	0.130	0.030–0.574	0.007	
Anti-GBM level	1.000	0.995–1.005	0.995	 	 	 	
eGFR	0.993	0.972–1.016	0.554	 	 	 	
Serum creatinine	1.000	0.999–1.001	0.912	 	 	 	
ANCA and anti-GBM positive	1.133	0.331–3.875	0.842	 	 	 	
Pneumonia	2.824	1.004–7.944	0.049	1.857	0.603–5.723	0.281	
Plasmapheresis	0.376	0.148–0.957	0.040	0.146	0.038–0.553	0.005	
High-dose MP	0.266	0.061–1.152	0.077	 	 	 	
Pulsed CTX	0.514	0.150–1.764	0.290	 	 	 	
High-dose MP/Pulsed CTX	0.396	0.131–1.195	0.100	 	 	 	
Red blood cell count	0.955	0.471–1.936	0.898	 	 	 	
Hemoglobin	1.000	0.974–1.026	0.989	 	 	 	
White blood cell count	0.991	0.884–1.112	0.878	 	 	 	
Granulocyte	1.074	1.018–1.133	0.009	1.218	1.071–1.385	0.003	
Absolute neutrophil count	1.025	0.998–1.052	0.071	 	 	 	
Lymphocyte	0.255	0.084–0.773	0.016	2.221	0.349–14.144	0.398	
Blood platelet count	0.999	0.995–1.002	0.527	 	 	 	
Prothrombin time	1.123	0.964–1.308	0.137	 	 	 	
International normalized ratiodetermination	2.569	0.446–14.814	0.291	 	 	 	
Activated partial theomboplastin time	1.058	0.993–1.127	0.079	 	 	 	
Fibrinogen determination	1.060	0.818–1.373	0.661	 	 	 	
Fibrinogen degradation product	1.023	0.989–1.058	0.183	 	 	 	
D-Dimer	1.002	0.999–1.005	0.152	 	 	 	
Total bilirubin	0.966	0.842–1.110	0.628	 	 	 	
Direct bilirubin	1.061	0.857–1.312	0.588	 	 	 	
Alanine transaminase	1.007	0.989–1.024	0.449	 	 	 	
Aspartate transaminase	1.020	1.009–1.032	<0.001	1.007	0.990–1.024	0.429	
Total protein	0.969	0.913–1.027	0.286	 	 	 	
Albumin	0.845	0.746–0.956	0.008	0.794	0.658–0.960	0.017	
Globin	1.025	0.965–1.088	0.428	 	 	 	
Urea	1.027	0.991–1.064	0.140	 	 	 	
Uric acid	1.001	0.997–1.005	0.478	 	 	 	
C-reactive protein	1.002	0.975–1.029	0.895	 	 	 	
eGFR: estimated glomerular filtration rate; Anti-GBM: anti-glomerular basement membrane; ANCA: antineutrophil cytoplasmic antibody; MP: methylprednisolone; CTX: cyclophosphamide.

p < 0.05 was considered as significant. Significant P values are represented in bold. Each parameter that was significant in univariable analysis, was analyzed in a multivariable analysis. Multivariable analysis is adjusted for sex, pneumonia, plasmapheresis, granulocyte, lymphocyte, aspartate transaminase and albumin.

Table 5. Univariable and multivariable cox analysis for 8-year survival.

Variables	Univariable analysis	Multivariable analysis	
HR	95%Cl	P value	HR	95%Cl	P value	
Age	1.033	1.009–1.058	0.007	1.033	1.002–1.066	0.035	
Sex	0.555	0.254–1.210	0.139	 	 	 	
Anti-GBM level	1.001	0.997–1.005	0.647	 	 	 	
eGFR	0.999	0.983–1.016	0.917	 	 	 	
Serum creatinine	1.000	0.999–1.001	0.517	 	 	 	
ANCA and Anti-GBM positive	1.670	0.618–4.512	0.312	 	 	 	
Pneumonia	2.013	0.871–4.654	0.102	 	 	 	
Plasmapheresis	0.366	0.163–0.823	0.015	0.309	0.112–0.850	0.023	
High-dose MP	0.359	0.123–1.045	0.060	 	 	 	
Pulsed CTX	0.404	0.138–1.187	0.099	 	 	 	
High-dose MP/Pulsed CTX	0.405	0.162–1.012	0.053	 	 	 	
Red blood cell count	1.047	0.527–2.081	0.896	 	 	 	
Hemoglobin	1.005	0.980–1.03	0.715	 	 	 	
White blood cell count	0.972	0.881–1.073	0.574	 	 	 	
Granulocyte	1.060	1.012–1.109	0.013	1.112	1.008–1.228	0.034	
Absolute neutrophil count	1.021	0.992–1.051	0.165	 	 	 	
Lymphocyte	0.223	0.082–0.604	0.003	1.681	0.310–9.121	0.547	
Blood platelet count	0.999	0.996–1.001	0.340	 	 	 	
Prothrombin time	1.141	0.991–1.313	0.066	 	 	 	
International normalized ratiodetermination	3.217	0.662–15.641	0.147	 	 	 	
Activated partial theomboplastin time	1.047	0.988–1.110	0.121	 	 	 	
Fibrinogen determination	1.095	0.860–1.394	0.462	 	 	 	
Fibrinogen degradation product	1.031	1.000–1.063	0.052	 	 	 	
D-Dimer	1.002	0.999–1.004	0.166	 	 	 	
Total bilirubin	0.944	0.823–1.082	0.407	 	 	 	
Direct bilirubin	1.000	0.812–1.232	0.997	 	 	 	
Alanine transaminase	1.001	0.983–1.020	0.883	 	 	 	
Aspartate transaminase	1.019	1.008–1.031	0.001	1.015	1.000–1.030	0.053	
Total protein	0.991	0.942–1.043	0.734	 	 	 	
Albumin	0.855	0.771–0.949	0.003	0.915	0.812–1.032	0.147	
Globin	1.046	0.996–1.098	0.072	 	 	 	
Urea	1.026	0.996–1.057	0.093	 	 	 	
Uric acid	1.002	0.998–1.005	0.344	 	 	 	
C-reactive protein	1.002	0.975–1.029	0.895	 	 	 	
eGFR: estimated glomerular filtration rate; Anti-GBM: anti-glomerular basement membrane; ANCA: antineutrophil cytoplasmic antibody; MP: methylprednisolone; CTX: cyclophosphamide.

p < 0.05 was considered as significant. Significant P values are represented in bold. Each parameter that was significant in univariable analysis, was analyzed in a multivariable analysis. Multivariable analysis is adjusted for age, plasmapheresis, granulocyte, lymphocyte, aspartate transaminase and albumin.

3.6. Complications of plasmapheresis

Twelve patients encountered one or more episodes of anaphylaxis, manifested as skin rash, itching, coughing and dyspnea, which were successfully managed with iv. dexamethasone, iv. calcium gluconate, oxygen therapy and cessation of treatment. One patient presented symptomatic hypocalcemia and numbness of extremities, which were relieved by iv. calcium gluconate. Other reported complications of plasmapheresis such as hypovolemia, depletion coagulopathy and access-associated complications, were not encountered in our study.

4. Discussion

This cohort study suggested that plasmapheresis was independently associated with improved in-hospital outcomes and long-term survival in anti-GBM disease. Patients who started plasmapheresis at lower serum creatinine or anti-GBM antibody levels had a better prognosis. According to our results, more than 10 sessions of plasmapheresis were not associated with incremental benefit in in-hospital outcomes, while patients who received 6–10 sessions of plasmapheresis had already achieved a maximum reduction in primary outcome risk in anti-GBM disease. ANCA positivity, hemoptysis, high-dose MP, and pulsed CTX were not related to patient outcomes in anti-GBM disease.

Given the rareness of this disorder, understanding on the epidemiology and therapeutic strategy of anti-GBM disease is still limited. The most well-recognized predictor of patient outcome is the severity of kidney dysfunction at presentation [9]. Anti-GBM disease patients who progressed to ESRD had a higher serum creatinine level at admission [10] and initial renal replacement therapy (RRT) was associated with a risk of all-cause mortality [11]. Serum creatinine was recognized as a predictor for kidney recovery, independent of biopsy findings [12]. Our research similarly showed that low eGFR at admission was an independent risk factor for adverse outcomes. Other literature-reported prognosticators, including hypertension and dyslipidemia [10,11,13] are, however, not echoed by our results. In this cohort, 22.4% of the enrolled patients were also positive for ANCAs. Anti-GBM antibodies have a narrow distribution range in the human body, mainly targeting the basement membrane of glomeruli and alveoli, while ANCAs can damage the endothelium of small/medium-sized vessels and can involve almost all systems and multiple organs [14]. A previous small-scale study involving 23 anti-GBM disease and 20 double-positive patients showed that there was no significant between-group difference in renal survival [15]. Another multicenter European cohort of 41 patients with anti-GBM disease and 37 double-positive patients recorded similar patient survival [16]. As per our observation, double-positive patients had higher serum creatinine at admission and were more likely to be prescribed pulsed CTX, which is of no surprise, as CTX is the fundamental treatment in most acute-phase ANCA-associated vasculitis (AAV) patients. In accordance with previous reports, double-positive patients in our study had a similar short-term prognosis to anti-GBM patients. However, given that AAV has a higher tendency of disease relapse, the long-term prognosis and optimum treatment strategies for double-positive patients require future research.

Plasmapheresis is a therapeutic intervention that involves extracorporeal removal or exchange of blood plasma and its components using semipermeable membranes. An early pilot study involving 17 patients observed a more rapid decrease in circulating anti-GBM antibody and improvement in renal function in patients treated with plasmapheresis in addition to immunosuppression [17]. In recent decades, plasmapheresis has been established as the cornerstone of therapy in anti-GBM disease [7]. Both renal and patient prognosis have been substantially improved since the wide application of plasmapheresis [3]. Our study showed that plasmapheresis was beneficial for not only in-hospital events but also long-term survival in adjusted models. It is suggested that plasmapheresis should be implemented early in the course of disease [18]. Consistently, we found that timely initiation of plasmapheresis at a lower level of serum creatinine or anti-GBM antibody could achieve better outcomes. The 2021 KDIGO glomerular diseases guideline recommends plasma exchange should be performed until anti-GBM titers are no longer detectable [7]. The ASAP guidelines recommend a minimum duration of 10–20 days of plasmapheresis treatment for anti-GBM disease [6], but in daily practice, the suggested dosage sometimes cannot be fully achieved. Compared with patients who did not receive it at all, the use of plasmapheresis in our study was always associated with a decreased risk of the primary outcome, irrespective of the number of plasmapheresis procedures performed. Notably, spline analysis showed that more than 10 sessions of plasmapheresis were not associated with incremental benefit in the primary outcome, while 5 to 10 sessions of treatment had already achieved maximum risk reduction. As our study reveals, a full course of 10–20 sessions might not be necessary for all patients, and the dosage of plasmapheresis should be flexible and tailored case by case based on clinical status and the remission of glomerular or pulmonary injury. Although anti-GBM antibody level might not be unparallel to the severity of disease, it could serve as an important marker for treatment planning, while the threshold titer to start or terminate plasmapheresis remains under investigated.

In addition to removing circulating antibodies by plasmapheresis, immunosuppressive therapy to further prevent antibody production is the mainstay of anti-GBM disease treatment [7]. The classical approach is a combination of corticosteroids and cytotoxic drugs such as CTX. Like many other active autoimmune diseases requiring urgent management, immunosuppressive therapy for anti-GBM disease could start with intravenous MP pulses (0.5–1 g/d) for 3 days, followed by oral prednisone which tapes down over time. CTX could be given either intravenously or orally, with a total accumulated dosage of 0.5–1 g/m2 [19]. The equivalence of daily oral and pulsed intravenous CTX in AAV has been confirmed by a large randomized control trial [20], which still remains inconclusive in anti-GBM disease. In this study, all 107 patients received corticosteroids and/or CTX, while only 33.6% received pulsed MP (>0.5/d), and 24.3% received pulsed CTX. Given the low incidence of relapse for anti-GBM disease [8], long-term use of CTX is usually not needed, making the rapid accumulation of CTX dosage by the oral route less an issue. The evidence for pulsed MP in anti-GBM disease is limited. Some scholars have even proposed that if plasmapheresis could be initiated early, high-dose intravenous corticosteroids are not required [3]. Our results did not support the use of high-dose MP or pulsed CTX, as neither of them were associated with improved in-hospital outcome or long-term patient survival. Apart from those classical immunosuppressants, the use of rituximab has also been reported by several small studies as either ‘add-on’ to standard therapy or as a substitute for CTX, but renal outcomes were not significantly improved [21,22].

One of our limitations is that the patients only used CTX and corticosteroids, and this study was unable to examine other immunosuppressants, such as rituximab or mycophenolate mofetil. Second, as we had been focusing on clinical parameters, the prognostic value of pathological features from renal biopsy was beyond this study’s scope. As renal biopsy was only performed in some of the patients, potential related disease such as Alport syndrome, membranous nephropathy, IgA nephropathy, as well as seronegative variant of anti-GBM disease, could not be sufficiently ruled out on pathological level. Third, the decision to start or stop plasmapheresis might be a reflection of disease severity or influenced by socioeconomic factors; therefore, the results were more indicative of association rather than causality. Meanwhile, the single-center retrospective nature and limited sample size comprised the power of the study, where the confounding factors might not be sufficiently adjusted. As multivariate analysis on number of plasmapheresis sessions and primary outcome were not performed due to limited sample size, the findings should be regarded as hypothesis-generating, which warrants prospective controlled studies to account for heterogeneity and formulate personalized therapeutic strategies for different patient subgroups.

5. Conclusions

This cohort study of 107 patients suggested that plasmapheresis was protective for both in-hospital outcomes and long-term survival in anti-GBM disease. Patients who initiated plasmapheresis at lower serum creatinine and lower GBM antibody levels had a better prognosis. A course of 10–20 days of treatment might not be necessary for all patients, as 5–10 sessions of plasmapheresis in this study seemed to have achieved maximum risk reduction for the primary outcome. According to our results, one should be cautious to prescribe high-dose MP or pulsed CTX, which was found to be unrelated to anti-GBM patient prognosis, especially for those who already received plasmapheresis. Multicenter cooperation is needed to assemble a large cohort of anti-GBM patients to validate the current findings and define optimum treatment strategies.

Acknowledgements

None.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Informed consent statement

Patient informed consent was waived by the Institutional Review Board due to the retrospective design.

Author contributions

Conceptualization: ZY, ZL, YY, FP. Data curation: LY, WY, WW, YL, LC, LJ, HY. Formal analysis: LY, ZY, WY, WB. Funding Acquisition: ZY. Supervision: ZY, YY, ZL, FP. Writing-original draft: LY, WW, ZY. Writing-review/editing: all coauthors.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.
==== Refs
References

1 Hellmark T, Segelmark M. Diagnosis and classification of Goodpasture’s disease (anti-GBM). J Autoimmun. 2014;48–49 :108–112. doi: 10.1016/j.jaut.2014.01.024.
2 Jennette JC. Rapidly progressive crescentic glomerulonephritis. Kidney Int. 2003;63 (3 ):1164–1177. doi: 10.1046/j.1523-1755.2003.00843.x.12631105
3 McAdoo SP, Pusey CD. Anti-glomerular basement membrane disease. Clin J Am Soc Nephrol. 2017;12 (7 ):1162–1172. doi: 10.2215/CJN.01380217.28515156
4 Canney M, O’Hara PV, McEvoy CM, et al. Spatial and temporal clustering of anti-glomerular basement membrane disease. Clin J Am Soc Nephrol. 2016;11 (8 ):1392–1399. doi: 10.2215/CJN.13591215.27401523
5 Cui Z, Zhao J, Jia XY, et al. Anti-glomerular basement membrane disease: outcomes of different therapeutic regimens in a large single-center Chinese cohort study. Medicine (Baltimore). 2011;90 (5 ):303–311. doi: 10.1097/MD.0b013e31822f6f68.21862934
6 Connelly-Smith L, Alquist CR, Aqui NA, et al. Guidelines on the use of therapeutic apheresis in clinical practice – evidence-based approach from the Writing Committee of the American Society for Apheresis: the Ninth Special Issue. J Clin Apher. 2023;38 (2 ):77–278. doi: 10.1002/jca.22043.37017433
7 Rovin BH, Adler SG, Barratt J, et al. KDIGO 2021 clinical practice guideline for the management of glomerular diseases. Kidney Int. 2021;100 (4 ): s1–S276. doi: 10.1016/j.kint.2021.05.021.34556256
8 Levy JB, Turner AN, Rees AJ, et al. Long-term outcome of anti-glomerular basement membrane antibody disease treated with plasma exchange and immunosuppression. Ann Intern Med. 2001;134 (11 ):1033–1042. doi: 10.7326/0003-4819-134-11-200106050-00009.11388816
9 van Daalen EE, Jennette JC, McAdoo SP, et al. Predicting outcome in patients with anti-GBM glomerulonephritis. Clin J Am Soc Nephrol. 2018;13 (1 ):63–72. doi: 10.2215/CJN.04290417.29162595
10 Marques C, Carvelli J, Biard L, et al. Prognostic factors in anti-glomerular basement membrane disease: a multicenter study of 119 patients. Front Immunol. 2019;10 :1665. doi: 10.3389/fimmu.2019.01665.31396214
11 Ge Y, Liu K, Yang G, et al. Clinicopathological characteristics and outcome predictors of anti-glomerular basement membrane glomerulonephritis. Ren Fail. 2022;44 (1 ):2037–2045. doi: 10.1080/0886022X.2022.2147673.36408940
12 Kuang H, Zhao YY, Wang JW, et al. Evaluation of the risk prediction models in predicting kidney outcomes in antiglomerular basement membrane disease. Kidney Int Rep. 2024;9 (3 ):624–634. doi: 10.1016/j.ekir.2023.12.011.38481502
13 Zhu M, Wang J, Le W, et al. Relationship between anti-GBM antibodies and kidney outcomes in patients with anti-GBM disease. J Nephrol. 2022;36 (3 ):789–797. doi: 10.1007/s40620-022-01508-5.36427163
14 Geetha D, Jefferson JA. ANCA-associated vasculitis: core curriculum 2020. Am J Kidney Dis. 2020;75 (1 ):124–137. doi: 10.1053/j.ajkd.2019.04.031.31358311
15 Hu X, Shen C, Meng T, et al. Clinical features and prognosis of MPO-ANCA and anti-GBM double-seropositive patients. Front Immunol. 2022;13 :991469. doi: 10.3389/fimmu.2022.991469.36389826
16 McAdoo SP, Tanna A, Hrušková Z, et al. Patients double-seropositive for ANCA and anti-GBM antibodies have varied renal survival, frequency of relapse, and outcomes compared to single-seropositive patients. Kidney Int. 2017;92 (3 ):693–702. doi: 10.1016/j.kint.2017.03.014.28506760
17 Johnson JP, Moore J, Jr., Austin HA, et al. Therapy of anti-glomerular basement membrane antibody disease: analysis of prognostic significance of clinical, pathologic and treatment factors. Medicine (Baltimore). 1985;64 (4 ):219–227. doi: 10.1097/00005792-198507000-00003.3892220
18 Cervantes CE, Bloch EM, Sperati CJ. Therapeutic plasma exchange: core curriculum 2023. Am J Kidney Dis. 2023;81 (4 ):475–492. doi: 10.1053/j.ajkd.2022.10.017.36775691
19 Ponticelli C, Calatroni M, Moroni G. Anti-glomerular basement membrane vasculitis. Autoimmun Rev. 2023;22 (1 ):103212. doi: 10.1016/j.autrev.2022.103212.36252931
20 de Groot K, Harper L, Jayne DR, et al. Pulse versus daily oral cyclophosphamide for induction of remission in antineutrophil cytoplasmic antibody-associated vasculitis: a randomized trial. Ann Intern Med. 2009;150 (10 ):670–680. doi: 10.7326/0003-4819-150-10-200905190-00004.19451574
21 Heitz M, Carron PL, Clavarino G, et al. Use of rituximab as an induction therapy in anti-glomerular basement-membrane disease. BMC Nephrol. 2018;19 (1 ):241. doi: 10.1186/s12882-018-1038-7.30236081
22 Touzot M, Poisson J, Faguer S, et al. Rituximab in anti-GBM disease: a retrospective study of 8 patients. J Autoimmun. 2015;60 :74–79. doi: 10.1016/j.jaut.2015.04.003.25953709
