Patient demographics
Patient characteristics are summarized in Table 1. Median patient age was 39 (IQR 28-48), with 19.5% being older than 50 years of age and 1.8% ≥ 65 years old. Recipients were 77.6% male; 6.6% were diabetic. All donors were living; 16.2% were related; 5.5% of patients were previously transplanted; and 3.7% had pretransplant donor-specific antibodies (DSA). Patients were biopsied from one day to 18 years post-transplant. The median time for biopsy post-transplantation was 150 (IQR 30-940) days.
Table 1: Clinical characteristic of recipients
Characteristic
|
value
|
Median age, years
|
39 (IQR 28-48)
|
> 50 years old
|
19.5%
|
Males
|
77.6%
|
Diabetes
|
6.6%
|
Living donor
|
100%
|
Related donor
|
16.2%
|
Serum creatinine at biopsy (mg/dl)
|
2.0 (IQR 1.6-2.6)
|
Previous transplant
|
5.5%
|
Pretransplant DSA positive
|
3.7%
|
Noncompliant
|
6.6%
|
Time of biopsy post-transplantation, days
|
150, range 1 to 6570
(IQR 30-940)
|
Maintenance immunosuppression
|
CNI (tacrolimus/cyclosporine), MMF, steroid
|
62.1%
|
CNI (tacrolimus/cyclosporine), steroid
|
37.9%
|
Indication for biopsy:
|
Primary nonfunction
|
14.1%
|
Deterioration of graft function
|
77.9%
|
Proteinuria
|
7.9%
|
Abbreviations: Continuous variables of age and serum creatinine and time
of biopsy are expressed as median and interquartile range. IQR, interquartile
range. CNI: calcineurin inhibitor (tacrolimus/cyclosporine); MMF:
mycophenolate mofetil; DSA, Donor-specific antibody.
In 2019, 204 patients had biopsies ≤ 365 days after transplantation (early biopsies) and 97 patients after 365 days (late biopsies). The follow-up identified an additional 131 patients from 2019 that were biopsied in 2020. The 2020 biopsies used in this study had a median post-transplant time of 1095 (IQR 450 to 2464) days and did not include any specimens from patients transplanted after January 1, 2020.
Pathology results
Figure 2 shows the distribution of 2019 diagnoses. The most common diagnosis was acute TCMR at 23.1%, followed by AKI at 14.8%, IF/TA at 11.4%, recurrent or de novo KD at 8.6%, TG at 7.6%, and CNI toxicity at 6.9%. Other specific diagnoses occurred at a frequency of less than 4%. Active C4d+ AMR was diagnosed in 8.6% of patients.
Twenty-three patients were diagnosed with recurrent or de novo KD, and eleven of these 23 were FSGS. All FSGS occurred in the late biopsy period over a range of 730 to 3650 days.
Nineteen patients were diagnosed with CNI toxicity. In the early biopsy period, CNI toxicity consisted of a TMA (n=11) or isometric tubular vacuolization (n=1). In the late biopsy period (n=7), CNI toxicity consisted of IF/TA with nodular arteriolar hyalinosis and sometimes segmental glomerulosclerosis.
Table 2 shows the distribution of diagnoses in early and late biopsies. Most patients with AKI and all patients with cortical infarction were found in early biopsies. Seventeen percent of AKI was seen after 100 days, and 3% after 12 months. These later AKI biopsies did not show features of CNI toxicity or infection, and the cause was unknown.
Table 2: Pathological diagnoses in early and late transplant biopsies.
Pathological lesions
|
Early biopsies ≤ one year (n=204)
|
Late biopsies > one year (n=97)
|
Early vs Late
P-value
|
AKI
|
56 (27.5%)
|
2 (2.1%)
|
<0.001
|
Infarction
|
8 (3.9%)
|
1 (1.0%)
|
0.34
|
Acute TCMR
|
69 (33.8%)
|
9 (9.3%)
|
<0.001
|
AMR C4d+
|
17 (8.3%)
|
9 (9.3%)
|
0.98
|
Chronic TCMR
|
5 (2.5%)
|
6 (6.2%)
|
0.22
|
TG
|
4 (2.0%)
|
19 (19.6%)
|
<0.001
|
IF/TA
|
13 (6.4%)
|
23 (23.7%)
|
<0.001
|
CNI toxicity
|
12 (5.9%)
|
7 (9.5%)
|
0.87
|
Recurrent or de novo KD
|
8 (3.9%)
|
17 (17.5%)
|
<0.001
|
Acute pyelonephritis
|
7 (3.4%)
|
1 (1.0%)
|
0.43
|
BK virus nephropathy
|
5 (2.5%)
|
3 (3.1%)
|
0.95
|
Abbreviations: TCMR, T cell-mediated rejection; AMR, antibody-mediated rejection; TG, transplant glomerulopathy; IF/TA, interstitial fibrosis/tubular atrophy; AKI, acute kidney
injury; CNI, calcinurin inhibitor; KD, kidney disease.
The frequency of acute TCMR was 34% in the early biopsies compared to 9% in late biopsies, a significant difference, P<0.001. The median time of biopsy of acute TCMR was 60 days post-transplantation (IQR 12 to 202 days) but with 14 cases (20%) being diagnosed sporadically at one to 10 years. Acute TCMR tended to be mild, with 76% being classified as grade I tubulointerstitial disease and 26% as grade II cellular rejection with vascular involvement.
Seven acute TCMR patients were noncompliant, and 71 were compliant. The two groups showed no significant differences in the histologic scores of inflammation (P=0.12), tubulitis (P=0.59), or vasculitis (p=0.48), and there was no difference in their rates of graft failure (noncompliant one failure, compliant 11 failures, P=0.17).
Active AMR began to be seen in the first year and overlapped with the early first year peak of acute TCMR and AKI (Figure 3). Active AMR was relatively equally distributed between early and late biopsies and occurred at a frequency of just over 8% of biopsies over a post-transplant period of 10 years.
TG and IF/TA were found mainly in late biopsies or late in the first year post-transplantation. Figure 4 compares the frequency of diagnosis of the chronic conditions of TG, IF/TA, chronic TCMR, and recurrent or de novo KD. The most common diagnoses in the late period were IF/TA at 23.7% and TG at 19.6%, with a ratio of active AMR to TG of 1:2.4 (42%).
The 2020 biopsies of previously unbiopsied 2019 patients consisted of the following diagnoses with their median post-transplant times (and IQR): non-specific changes, n=6, 1538 days (428-3467); AKI, n=3, 150 days (150-650); Acute TCMR, n=32, 392 days (270-750); active AMR, n=15, 1825 days (750-2555); Chronic TCMR, n=11, 1825 days (750-2190); TG, n=15, 2555 days (1460-3650); IF/TA, n=20, 2372 days (836-3293); CNI toxicity, n=5, 548 days (290-923); recurrent or de novo disease, n=14, 1095 days (725-1460); pyelonephritis, n=6, 730 days (341-2580); BK nephropathy, n=3 (240-750). The 2020 biopsies reflect AKI and acute TCMR complicating transplants performed toward the end of 2019 and chronic conditions that were clinically silent in 2019.
Allograft failures
By the end of 2020, graft failure occurred in 117 patients (Table 3). In the early post-transplant period, forty-nine grafts were lost, with the most frequent diagnoses being acute TCMR, n=11; AKI, n=8; and infarction, n=7. After receiving second transplants, two patients with active AMR lost grafts within 7 days because of pre-existing DSA and hyperacute rejection.
Table 3. Graft failures by diagnosis, age, hemodialysis failure, and post-transplant time to graft loss.
Diagnosis
|
n (%)
all-cause
|
n (%)
HD
|
Patient age
years
|
Transplant
time days
|
AKI
|
8 (6.8)
|
4 (4.5)
|
44 (7-50)
|
16 (7-30)
|
Infarction
|
7 (6.0)
|
5 (5.7)
|
40 (37-43)
|
14 (7-22)
|
Acute TCMR
|
11 (9.4)
|
7 (8.0)
|
38 (34-50)
|
120 (12-333)
|
Active AMR
|
17 (14.5)
|
16 (18.2)
|
41 (33-44)
|
1460 (14-2555)
|
Chronic TCMR
|
8 (6.8)
|
7 (8.0)
|
41 (33-44)
|
1245(1003-1909)
|
TG
|
16 (13.7)
|
13 (14.8)
|
40 (33-50)
|
2372 (1027-2646)
|
IF/TA
|
28 (23.8)
|
22 (25.0)
|
41 (30-47)
|
1552 (548-3102)
|
CNI toxicity
|
3 (2.6)
|
3 (3.4)
|
62 (51-56)
|
910 (560-1185)
|
Recurrent or de novo KD
|
11 (9.4)
|
6 (6.8)
|
36 (29-47)
|
810 (360-1825)
|
pyelonephritis
|
3 (2.6)
|
2 (2.3)
|
52 (38-55)
|
1095 (593-1368)
|
BK virus nephropathy
|
5 (4.3)
|
3 (3.4)
|
58 (57-64)
|
365 (340-740)
|
|
117
|
88 (75.2)
|
|
|
Values for age and transplant time are for all-cause failure and are expressed as median (interquartile range). Abbreviations: HD, hemodialysis; DWFG, death with functional graft; AKI, acute kidney injury; TCMR, T cell-mediated rejection; AMR, antibody-mediated
rejection; TG, Transplant glomerulopathy; IF/TA, interstitial fibrosis and tubular atrophy;
CNI calcineurin inhibitor; KD, kidney disease.
The pathology of graft loss because of acute TCMR was complicated. Three of the eleven patients had a vasculitis. One patient had a Banff grade IIA acute TCMR on day six that progressed to a TMA with cortical infarction and HD on day 66 post-transplantation. Another patient had a Banff grade IB acute TCMR at 365 days that advanced to IF/TA grade III and HD by day 1135. Four of the eleven acute TCMR failures were DWFG.
Graft loss with AKI presented a similar complicated picture. Four of the eight failures were DWFG. One patient had graft biopsies showing AKI on days 90 and 120 and then IF/TA grade III requiring HD at 455 days. Another patient with AKI and grade I IF/TA on day 1095 progressed to IF/TA grade III and HD at 1460 days.
In the late period, sixty-eight patients lost grafts. The most common diagnoses were IF/TA, n=28; TG, n=16; C4d+ active AMR, n=14; and recurrent or de novo KD, n=11. DWFG was responsible for 24.8% of graft loss and occurred nearly equally in the early (n=15) and late (n=14) post-transplant periods. The attributed cause of 13 cases of DWFG, including four COVID-19 cases, was infection (Table 4). Four patients over 50 years of age had sudden deaths that may have been myocardial.
Table 4. Death with a functional graft by biopsy diagnosis, number of deaths, age, post-transplant time, and causes of death.
Biopsy diagnosis
|
n
|
Age
years
|
Post-transplant
time days
|
Causes of death
|
AKI
|
4
|
41 (37-46)
|
15 (2-108)
|
Infection (2), COVID-19, unk
|
Infarction
|
2
|
26,53
|
7,42
|
Infection (2)
|
aTCMR
|
4
|
39 (33-40)
|
110 (9-232)
|
Infection, unk (3)
|
aAMR
|
1
|
54
|
22
|
Myocardial?
|
cTCMR
|
1
|
47
|
730
|
Unk
|
TG
|
3
|
48 (43-58)
|
1460 (958-2007)
|
COVID-19 (3)
|
IF/TA
|
6
|
50 (28-53)
|
970 (609-1695)
|
COVID-19, PTLPD, infection, myocardial ?, unk (2)
|
Recurrent/denovo KD
|
5
|
38 (36-41)
|
420 (240-2190)
|
Myeloma, AA amyloidosis, pancreatitis, myocardial?, unk
|
Pyelonephritis
|
1
|
52 (38-55)
|
1095 (593-1368)
|
Infection
|
BK virus nephropathy
|
2
|
58 (57-64)
|
365 (340-740)
|
Infection, myocardial ?
|
|
29
|
|
|
|
For more than two entries, values for age and post-transplant time are expressed as median (interquartile range). Abbreviations: HD, hemodialysis; AKI, acute kidney injury; aTCMR, acute T cell-mediated rejection; aAMR, active antibody-mediated rejection; cTCMR, chronic T cell-mediated rejection; TG, Transplant glomerulopathy; IF/TA, interstitial fibrosis and tubular atrophy; CNI calcineurin inhibitor; KD, kidney disease; unk, unknown; PTLD, post-transplant lymphoproliferative disease.
Estimated Iraqi one- and five-year failure rates for all-cause, HD, and death are shown in Table 5 together with the 2000 and 2010 rates for living-donor transplants in the United States (US) reported in the 2017 US Renal Data Service (USRDS) Annual Data Report [19]. The Iraqi data resembles living-donor failure rates in the US in 2000 for both death and HD. It is notable that death and HD failure rates in both Iraqi and the US in 2000 are higher than the lowered rates achieved in the US by 2010.
Table 5: One- and five-year living-donor transplant failure rates. Estimated current Iraqi Kurdistan rates (95% confidence intervals) are compared with reported United States (US) outcomes in 2000 and 2010 [20].
|
One-year graft failure (%)
|
five-year graft failure (%)
|
Site, year
|
All-cause
|
HD
|
Death
|
All-cause
|
HD
|
Death
|
Iraq, 2019
|
9.1
(6.5-11.7)
|
6.3
(4.1-8.5)
|
2.9
(1.3-4.5)
|
23.8
(18.7-28.9)
|
17.7
(12.7-22.5)
|
7.4
(4.2-10.6)
|
US, 2000
|
7.0
|
5.0
|
2.6
|
22.3
|
15.2
|
10.6
|
US, 2010
|
3.7
|
2.4
|
1.4
|
15.3
|
9.6
|
7.3
|
Abbreviation: HD, hemodialysis
The median Iraqi graft survival for all-cause failures was ten years (95%CI: 8 to 12 years), and the death-censured median survival was 15 years (95%CI: 11 to 19 years). The length of the post-transplant period significantly correlated with the severity of IF/TA (Rs=0.770, P<0.001) and TG (Rs=0.464, P<0.001). Logistic regression (Table 6) showed that IF/TA and C4d positive IF staining significantly predicted HD but that acute TCMR and AKI did not. DWFG was not significantly related to sex, donor source, IF/TA, TG, C4d staining, AKI, or acute TCMR.
Table 6. Logistic regression models for hemodialysis graft failure
and death with a functional graft (DWFG).
Hemodialysis initial model
|
Variable
|
Odds ratio
|
P-value
|
95% CI
|
Age
|
1.014
|
0.25
|
0.991 to 1.037
|
Sex
|
0.484
|
0.04
|
0.242 to 0.967
|
Donor source
|
1.450
|
0.38
|
0.635 to 3.312
|
Acute TCMR
|
0.413
|
0.08
|
0.152 to 1.123
|
AKI
|
0.701
|
0.47
|
0.270 to 1.821
|
C4d+
|
2.264
|
0.04
|
1.044 to 6.576
|
IF/TA
|
1.935
|
0.000
|
1.375 to 2.719
|
TG
|
1.038
|
0.83
|
0.731 to 1.476
|
Hemodialysis final model
|
Sex
|
0.647
|
0.16
|
0.355 to 1.179
|
C4d+
|
3.427
|
0.01
|
1.325 to 8.865
|
IF/TA
|
2.957
|
0.000
|
1.734 to 2.927
|
DWFG initial model
|
Age
|
1.018
|
0.24
|
0.988 to 1.049
|
Sex
|
0.582
|
0.25
|
0.233 to 1.453
|
Donor source
|
0.632
|
0.48
|
0.178 to 2.246
|
Acute TCMR
|
0.492
|
0.27
|
0.138 to 1.754
|
AKI
|
1.339
|
0.60
|
0.453 to 3.962
|
C4d+
|
0.245
|
0.20
|
0.029 to 2.090
|
IF/TA
|
1.022
|
0.93
|
0.639 to 1.633
|
TG
|
1.112
|
0.68
|
0.672 to 1.843
|
DWFG final model
|
C4d+
|
0.338
|
0.30
|
0.044 to 2.586
|
Abbreviations: TCMR, T cell mediated rejection; AKI, acute
kidney injury; IF/TA, interstitial fibrosis and tubular atrophy; TG,
transplant glomerulopathy.