Results
Demographic, Clinical and Laboratory
data
We recruited a total of 91 kidney transplant recipients, 46 of them had
an RT-PCR confirmed COVID-19, and 45 of them did not have COVID-19
history (Table 1). Demographic, clinical, and laboratory data of
transplant recipients grouped according to COVID-19 status are shown in
Table 1. Both groups were similar regarding age and sex. Etiology of CKD
and donor type and post-transplant duration were also similar between
the two groups. However, patients with COVID-19 had a higher BMI, and
COVID-19 history in a household member was more common among them. Other
parameters were similar between the two groups.
The majority (95.6%) of the patients with COVID-19 were symptomatic,
and according to thorax computed tomography examination, 30 (65.2%)
patients had findings compatible with COVID-19. There was no need for
hospitalization in 12 (26.1%) patients; the remaining 34 (73.9%)
patients were hospitalized, 16 (34.8%) patients needed oxygen, and
three (6.5%) of them were followed up in the intensive care unit. Two
(4.3%) patients needed intubation. Except for one patient who died on
the 26th day of the infection, all patients recovered from COVID-19. The
hospitalization duration was 11.7±7.9 days (median:9 days, range:3-38
days). According to the COVID-19 severity index, two (4.3%) patients
were asymptomatic or presymptomatic, 15 (32.6%) patients had a mild
illness, 16 (34.7%) patients had a moderate illness, 10 (21.7%)
patients had a severe illness, and three (6.5%) patients had a critical
illness.
Seropositivity
Seropositivity rate and IgG levels among kidney transplant recipients
and controls stratified by COVID-19 status are shown in Table 2. Among
subjects with COVID-19 history, the SARS-Cov-2 IgG positivity rate and
IgG level of kidney transplant recipients were similar to that of the
control group. The frequency of COVID-19 related symptoms was more
common among kidney transplant recipients than that of the controls;
however, the frequency of pulmonary involvement assessed by computerized
tomography was similar between the two groups. There was no
statistically significant difference between the kidney transplant
recipients and controls in terms of the duration from RT-PCR to antibody
testing. (Table 2).
Among subjects without COVID-19 history, three kidney transplant
recipients had positive IgG antibodies, and two of them had a history of
COVID-19 in a household member. SARS-Cov-2 IgG antibody positivity rate
and IgG level of kidney transplant recipients were similar to that of
the control group (Table 2).
Predictors of antibody
positivity
We compared demographic, clinical, laboratory, and treatment-related
data of the transplant patients who developed antibodies with those who
did not (Table 3). The median duration between RT-PCR and antibody
testing was shorter (37.5 [IQR 20.5-57.8] vs 82.5 [IQR
52.3-105.0] days, p=0.01) in patients who had SARS-Cov-2 IgG
antibodies compared to that of the patients who do not have IgG
antibodies. There were no statistically significant differences among
the two groups regarding demographic, clinical, laboratory parameters.
Additionally, the cessation rate of different immunosuppressive drugs
was also similar between the two groups.
As an additional analysis, we looked at the correlation between
different laboratory parameters (peak CRP, peak ferritin, fibrinogen,
peak d-dimer, peak procalcitonin, e-GFR) and level of SARS-Cov-2 IgG
antibodies. There was no significant correlation between those
parameters (data not shown).
Finally, we analyzed the correlation between SARS-Cov-2 IgG antibody
levels and the duration between RT-PCR and antibody testing. The
antibody level in kidney transplant recipients and controls according to
duration following RT-PCR testing is shown in Figure 1. Visual
examination revealed that there was a trend toward lower antibody levels
in kidney transplant recipients with increasing post-infection duration.
There was a significant correlation between antibody level and duration
in transplant recipients (r=-0.532, p<0.001), however, there
was no statistically significant correlation between antibody level and
duration in controls (r=0.198, p=0.186). Additionally, we constructed a
multivariate regression model; we used antibody levels as the dependent
variable, and the study group along with the duration following RT-PCR
testing as the independent variables. This analysis showed that the
study group was not an independent determinant of antibody levels (data
not shown).