Efficacy of protein A immunoadsorption and therapeutic plasma exchange in ANCA-associated vasculitis with severe renal involvement: a retrospective study

Figures & data

Figure 1. Flow diagram illustrating study cohort. AAV: ANCA-associated vasculitis; PAIA: protein A immunoadsorption; TPE: therapeutic plasma exchange.

Table 1. Baseline characteristics of patients with AAV.

Characteristics	All (N = 48)	PAIA group (N = 18)	TPE group (N = 30)	p Value
Age, years	61.0 (52.0, 67.0)	61.0 (53.0, 66.0)	60.5 (52.0, 67.5)	.579
Female, n (%)	14 (29.2)	5 (27.8)	9 (30.0)	.870
Disease course, months	1.5 (1.0, 3.8)	1.5 (1.0, 3.5)	1.5 (1.0, 4.5)	.837
Hypertension, n (%)	17 (35.4)	9 (50.0)	8 (26.7)	.102
MPO-ANCA, n (%)	46 (95.8)	18 (100.0)	28 (93.3)	.521
ANCA titres, IU/mL	117.9 (81.1, 248.9)	124.3 (69.2, 739.1)	116.7 (81.4, 145.0)	.343
WBC, ×10^9/L	6.7 (5.3, 9.8)	6.7 (4.9, 9.0)	6.9 (5.7, 11.4)	.360
Hb, g/L	83.0 (67.5, 95.3)	85.0 (65.5, 96.0)	82.5 (69.8, 96.8)	.975
PLT, ×10^9/L	222.4 ± 95.6	226.9 ± 105.3	219.8 ± 91.1	.806
ALB, g/L	30.4 ± 5.1	32.0 ± 5.3	29.4 ± 4.9	.088
GLO, g/L	30.6 ± 6.0	30.6 ± 6.0	30.5 ± 7.2	.955
SCr, $\mathrm{\mu }$ mol/L	497.6 (321.3, 610.7)	419.1 (308.4, 522.6)	508.2 (317.2, 811.3)	.088
SCr > 500 $\mathrm{\mu }$ mol/L or RRT, n (%)	32 (66.7)	9 (50.0)	23 (76.7)	.058
eGFR, mL/min/1.73 m^2	9.8 (6.8, 16.7)	12.6 (9.1, 18.7)	9.5 (4.9, 16.5)	.074
BVAS	15.9 ± 3.1	15.9 ± 3.1	16.7 ± 2.5	.428
Induction therapy, n (%)
GC pulse therapy	42 (87.5)	17 (94.4)	25 (83.3)	.499
GC + CYC	47 (97.9)	17 (94.4)	30 (100)	.375
GC + CYC + RTX	1 (2.1)	1 (5.6)	0 (0)	.375

MPO: myeloperoxidase; ANCA: antineutrophil cytoplasmic antibody; WBC: white blood cells; Hb: haemoglobin; PLT: platelet; ALB: albumin; GLO: globulin; SCr: serum creatinine; RRT: renal-replacement therapy; eGFR: estimation glomerular filtration rate; BVAS: Birmingham Vasculitis Activity Score; GC: glucocorticoid; CYC: cyclophosphamide; RTX: rituximab.

Table 2. Baseline extrarenal organ involvement.

System involvement, no. (%)	PAIA group (N = 18)	TPE group (N = 30)	p Value
Constitutional	9 (50.0)	9 (30.0)	.166
Respiratory	13 (72.2)	24 (80.0)	.535
Ear, nose, throat	2 (11.1)	1 (3.3)	.281
Nervous	0 (0.0)	2 (6.7)	.263
Cutaneous	0 (0.0)	0 (0.0)	–
Eye, mucosa	1 (5.5)	1 (3.3)	.709
Cardiovascular	0 (0.0)	1 (3.3)	.434
Gastrointestinal	0 (0.0)	0 (0.0)	–

PAIA: protein A immunoadsorption; TPE: therapeutic plasma exchange.

Figure 2. Changes of (A) MPO-ANCA titres and (B) decline rate in PAIA group and TPE group before treatment and within 1 month of treatment (n = 17 in PAIA group, n = 17 in TPE group). (C) Trends of MPO-ANCA titres in two patients during PAIA treatment. (D) Changes in MPO-ANCA titres within 6 months after treatment in PAIA group (n = 13). (E) Changes in serum IgG, IgA and IgM levels before and after PAIA or TPE treatment (n = 13 in PAIA group, n = 6 in TPE group). *p < .05, **p < .01. (1-b) Before the first PAIA treatment; (1-a) after the first PAIA treatment; (2-b) before the second PAIA treatment; (2-a) after the second PAIA treatment; (3-b) after the second PAIA treatment before the third PAIA treatment; (3-a) after the third PAIA treatment; (4-b) before the fourth PAIA treatment; (4-a) after the fourth PAIA treatment; (5-b) before the fifth PAIA treatment; (5-a) after the fifth treatment; (6-b) before the sixth PAIA treatment; (6-a) after the sixth PAIA treatment. PAIA: protein A immunoadsorption; TPE: therapeutic plasma exchange; pre-PAIA: before PAIA treatment; post-PAIA: after PAIA treatment.

Figure 3. Kaplan–Meier’s curves for (A) all-cause mortality, (B) ESRD and (C) all-cause mortality or ESRD. There were 18 patients in the PAIA group and 30 patients in the TPE group. Significance was determined by the log-rank test. ESRD: end-stage renal disease; PAIA: protein A immunoadsorption; TPE: therapeutic plasma exchange.

Table 3. Cox regression analysis of risk factors predicting death due to AAV with severe kidney involvement.

	Univariable analysis			Multivariate analysis
Variable	HR	95%CI	p Value	HR	95%CI	p Value
Male	0.62	0.17–2.24	.470
Age > 60	5.89	1.32–26.39	.020	10.67	2.16–52.59	.004
Disease course, months	0.96	0.86–1.09	.543
BVAS	1.26	1.01–1.58	.042	1.08	0.83–1.39	.573
SCr, μmol/L	1.001	0.999–1.003	.236
WBC, ×10^9/L	1.01	0.90–1.14	.889
ALB, g/L	0.88	0.79–0.98	.017	0.85	0.75–0.96	.010
Pulmonary involvement	1.86	0.42–8.31	.417
GC pulse therapy	0.46	0.13–1.66	.237
PAIA/TPE	0.24	0.05–1.08	.063
Remission at 6 months	0.15	0.04–0.54	.004	0.16	0.04–0.70	.015

BVAS: Birmingham Vasculitis Activity Score; SCr: serum creatinine; WBC: white blood cells; ALB: albumin; GC: glucocorticoid; PAIA: protein A immunoadsorption; TPE: therapeutic plasma exchange.

Table 4. Cox regression analysis of risk factors predicting ESRD of AAV with severe kidney involvement.

	Univariable analysis			Multivariate analysis
Variable	HR	95%CI	p	HR	95%CI	P
Male	1.76	0.84–3.71	.135
Age > 60	1.08	0.46–2.58	.854
Disease course, months	1.04	0.99–1.08	.179
BVAS	1.11	0.94–1.31	.203
Hb, g/L	0.97	0.94–0.99	.018	0.96	0.94–0.99	.017
SCr, μmol/L	1.002	1.000–1.004	.016	1.002	1.000–1.004	.011
WBC, ×10^9/L	0.95	0.86–1.06	.372
ALB, g/L	1.01	0.93–1.11	.763
Pulmonary involvement	0.81	0.32–2.05	.66
GC pulse therapy	1.16	0.27–5.00	.841
PAIA/TPE	1.61	0.66–3.89	.294
Remission at 6 months	0.55	0.22–1.38	.205

BVAS: Birmingham Vasculitis Activity Score; Hb: haemoglobin; SCr: serum creatinine; WBC: white blood cells; ALB: albumin; GC: glucocorticoid; PAIA: protein A immunoadsorption; TPE: therapeutic plasma exchange.

Data availability statement

The data based on the results of the current study were obtained, and are accessible from the corresponding authors upon reasonable request.