THE EFFECT OF EOSINOPHIL AND BASOPHIL COUNTS ON MORTALITY IN
PATIENTS WITH COVID-19 INFECTION
SUMMARY
INTRODUCTION: The aim of this study investigated the effect of
eosinophil and basophil counts on mortality in patients with COVID-19
infection.
METHODS: Blood tests of 582 patients with RT-PCR test in an
oropharyngeal swab sample who were admitted to Diyarbakır Gazi Yaşargil
Training and Research Hospital between March 2020 and December 2020 were
retrospectively analysed. The patients were divided into two groups:
those who recovered and discharged and those who had a mortal course.
Demographic data, comorbid diseases, routine blood tests, and
haematological parameters were compared between both groups.
RESULTS: An eosinophil count of 0.01 ± 0.04 and basophil count of 0.0261
± 0.026 was observed in the patient group who had a mortal course at
first admission to the hospital, while the eosinophil count was 0.06 ±
0.12 and basophil count was 0.020 ± 0.017 in the recovered patient
group. On the fifth day after admission, the eosinophil count was 0.02 ±
0.07 and basophil count was 0.043 ± 0.042 in the patient group with a
mortal course, while the count of eosinophils was 0.13 ± 0.14 and
basophils was 0.023 ± 0.016 in the recovered patient group. In both
groups, the eosinophil and basophil counts on the fifth day increased
compared to the first day, and the eosinophil and basophil counts were
lower in those who had a mortal course on both the first and fifth day
(p < 0.05).
CONCLUSIONS: In our study, a significant decrease was observed in the
count of eosinophils and basophils in the mortal group of COVID-19
patients. Eosinopenia and basopenia may be parameters that can be used
to facilitate the diagnosis of COVID-19, and the depth of both
eosinopenia and basopenia is positively correlated with COVID-19
mortality.
WHAT’S KNOWN
Although there are studies showing the importance of eosinophil count in
COVID-19, it is still a controversial issue and the number of studies
evaluating basophil and eosinophil count together is limited. Although
there are studies indicating a decrease in the number of eosinophils and
basophils during the infection process, there are studies that found no
significant difference. There are studies reporting that improvement in
eosinopenia and basopenia may be an indicator of recovery from COVID-19,
but the data on this subject are also controversial.
WHAT’S NEW
It was determined that there was a significant decrease in the
eosinophil and basophil counts in COVID-19 patients, and it was observed
that eosinopenia and basopenia were deeper in patients with a mortal
course. While improvement in eosinopenia and basopenia was observed in
all patients, this increase was observed to be more pronounced in
patients who recovered. We think that our study will contribute to the
literature, as there are limited studies in which both basophils and
eosinophil counts are evaluated in detail in COVID-19 infection.
INTRODUCTION
COVID-19, which started in Wuhan province, China, in November 2019 and
quickly spread all over the world, was declared a pandemic by the World
Health Organisation on March 11. Those patients infected with severe
acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may progress as
asymptomatic or with symptoms severe enough to be admitted to the
intensive care unit. This virus can cause death in patients who develop
acute respiratory distress syndrome, as well as symptoms such as fever,
dry cough, shortness of breath, malaise, taste and smell disorders, and
myalgia (1). In many studies, treatment options have been evaluated, and
prognostic factors and important parameters that play a role in the
course of the disease have been investigated. These parameters are
associated with viral pathogenic mechanisms and the resulting cell or
organ damage (2).
Eosinophils are peripheral blood elements that have strong
pro-inflammatory effects and are involved in immunoregulation in many
infections, including viral infections (3). In the case of acute
infection, a dramatic decrease is observed in the count of circulating
eosinophils (4). Studies have shown a decrease in the count of
eosinophils in acute viral infection caused by SARS-CoV-2 (3, 5, 6), and
since eosinophil count can be used as a low-cost inflammation parameter
in this infection, it has attracted attention recently (7).
Unfortunately, the effect of eosinophil count on the course and severity
of the disease is still a controversial issue (5). Likewise, the role of
eosinophils count in recovery has not yet been fully elucidated. There
are studies reporting that improvement in eosinopenia may be an
indicator of recovery from COVID-19, but there are insufficient data on
this subject (8, 9).
Another peripheral blood element that plays an important role in
immunoregulation is basophils. In previous studies, it has been
demonstrated that basophils secrete IL-4 and IL-6 and strengthen the
immune system (10). During acute COVID-19 infection, dramatic changes
occur in the immune system (11). Basophils change the immune system and
cause hypersensitivity reactions, endocrinopathies, and haematological
disorders (12).
Although there have been studies indicating the importance of eosinophil
count in COVID-19, it is still a subject under investigation, and the
number of studies evaluating basophil and eosinophil counts together is
limited. In our study, we aimed to evaluate the prognostic importance of
both eosinophil and basophil counts in peripheral blood during COVID-19
infection and their relationship with mortality.
METHODS
Blood tests of 581 patients who were hospitalised in Diyarbakır Gazi
Yaşargil Training and Research Hospital between March and December 2020
and whose oropharyngeal swab samples were positive using RT-PCR were
retrospectively analysed. Ethics committee approval was obtained for
this study, dated 12/02/2021 and numbered 678. Patients aged 18–90
years with a haemogram examination, no haematological disease, no
infectious disease other than COVID-19, oxygen saturation below 92%,
lung findings in Thorax computed tomography (Thorax CT), and
hospitalised for at least 5 days were included in the study. Patients
under the age of 18 and over 90, those with incomplete examinations or
who did not complete the treatment process, patients with infections
other than COVID-19, patients with oxygen saturation above 92%, or
without pulmonary findings in Thorax CT were excluded from the study.
Haemogram (Mindray BC 6800, China) tests were performed in all patients
during routine blood tests at the time of first hospitalisation. Then,
the second haemogram test was performed on the fifth day of admission.
In addition, demographic data, comorbid diseases, length of stay, and
mortality information of the patients were noted. The patients were
divided into two groups: those who recovered and were discharged and
those who had a mortal course. Demographic data, comorbid diseases,
routine blood tests, and haematological parameters were compared between
both groups. In addition, haematological parameters performed on both
days 1 and 5 were compared.
Statistical analyses
The Statistical Package for the Social Sciences Version 21 Windows (SPSS
Inc., Chicago IL, USA) was used for statistical analyses. The normality
of data distribution was analysed using the Shapiro-Wilk test.
Descriptive statistics were expressed as the mean ± standard deviation.
The independent samples test was used to compare the data of the two
groups. Repeated measurements were compared with the paired t-test. P
< 0.05 was considered statistically significant. The frequency
of the data was evaluated with frequency tables.
RESULTS
While 358 (61.6%) of 581 patients who were diagnosed with SARS-CoV-2 in
the oropharyngeal swab sample and hospitalised with COVID-19 pneumonia
recovered and were discharged, 223 (38.4%) patients were mortal. We
found that the mean age of these patients was 56.86 ± 19.38 (16–90 age
range). The mean age of the 358 patients who recovered and were
discharged was 47.7 ± 16.7, and the mean age of the 223 patients who
were mortal was 71.9 ± 12.9. The difference in age was significant (p
< 0.001). There were 324 male (55.8%) and 257 female (44.2%)
patients. Of these, 136 male and 87 female patients were mortal.
Demographic characteristics and Co-Morbid conditions of patients is
shown in Table 1. The most common accompanying comorbid diseases were
diabetes mellitus (43.7%) and hypertension (40.2%), followed by
coronary artery disease (35.4%), chronic kidney failure (15.3%),
chronic obstructive pulmonary disease (12.7%), cerebrovascular disease
(10.1%), and malignancy (3.7%). There was a significant difference in
the number of patients with comorbidities (p < 0.001) between
patient groups who recovered and those who had a mortal course. There
was more mortal in COVID-19 patients with diabetes mellitus,
hypertension, coronary artery disease, chronic renal failure, chronic
obstructive pulmonary disease, and cerebrovascular disease (p
< 0.001). In contrast, there was no significant difference
between the mortality and recovery groups in terms of progression in
COVID-19 patients with malignancy (p > 0.05). While 52.2%
of the discharged patients were smokers, 44.3% of the mortal patients
were smokers. As a result, there was no significant difference between
the two groups in terms of smoking (p > 0.05).
Routine blood tests of patients on the first hospitalisation day are
shown in Table 2. Glucose, creatinine, ferritin, procalcitonin, d dimer,
troponin, ALT, and CRP values were higher in those with mortality than
in those who recovered and were discharged (p < 0.001).
The haematological examinations performed on the first day of
hospitalisation are shown in Table 3, and the haematological
examinations performed on the fifth day are shown in Table 4.
Eosinopenia was observed in 376 patients and basopenia in 252 patients,
according to the haematological parameters performed on the first day of
hospitalisation. Interestingly, the eosinophil count in 273 patients and
the basophil count in 22 patients was 0. On the fifth day, eosinopenia
was observed in 225 patients and basopenia in 149 patients. While the
eosinophil count was 0.01 ± 0.04 and basophil count was 0.0261 ± 0.026
in the patient group with a mortal course on the first day, the
eosinophil count was 0.06 ± 0.12 and basophil count was 0.020 ± 0.017 in
the recovered patient group. On the fifth day, the eosinophil count was
0.02 ± 0.07 and basophil count was 0.043 ± 0.042 in the patient group
with a mortal course, while the eosinophil count was 0.13 ± 0.14 and
basophil count was 0.023 ± 0.016 in the recovered patient group. The
eosinophil and basophil counts on the fifth day increased compared to
the first day in both groups, and the eosinophil and basophil counts
were lower in the patient group with a mortal course compared to the
recovered patient group on both the first day and the fifth day (p
< 0.05). No difference was observed in the neutrophil, white
blood cell, lymphocyte, platelet count, and haematocrit levels (p
> 0.05) between the two groups on the first day. Similarly,
there was no difference between lymphocyte, platelet counts, and
haematocrit levels performed on the fifth day (p > 0.05).
In contrast, the white blood cell and neutrophil counts were higher in
those with mortality on the fifth day (p < 0.001).
The change in eosinophil and basophil counts on the first and fifth days
is shown in Table 5, and the corresponding graphs are shown in Figure 1.
All patients during COVID-19 infection, the eosinophil count in the
blood was determined as 0.042 ± 0.10 and 0.09 ± 0.13 on the first and
fifth day, respectively, and it increased on the fifth day compared to
the first day (p < 0.001). The basophil count was 0.022 ±
0.021 on the first day and 0.031 ± 0.030 on the fifth day, showing an
increase on the fifth day compared to the first day (p <
0.001).
DISCUSSION
In our study, eosinopenia and basopenia developed on the first day of
hospitalization in the vast majority of COVID-19 patients, but the count
of eosinophils and basophils increased on the fifth day compared to the
first day in those who recovered, but this increase was less in the
mortal group.
It is known from previous studies that there is a decrease in the
eosinophil count during COVID-19 infection. In some studies, the
incidence of eosinopenia has been reported to be between 50.8 and 94%
(13). However, while we detected 64.7% eosinopenia in the
haematological tests performed on the first day in our hospitalised
COVID-19 patients, 43.8% had eosinopenia in the tests performed on the
fifth day. There is variability in eosinophil count, with some studies
showing 0 in some patients at the onset of infection (3). Similarly, in
our study, we found that the eosinophil count was 0 in approximately
47% of our patients upon initial admission to the hospital. At the same
time, we found that basopenia, which was 43.3% on the first day of
hospitalisation, decreased to 25.6% on the fifth day.
Zhang et al. emphasised that eosinopenia commonly develops during
COVID-19 infection and that eosinopenia can be a parameter used in
diagnosis. In their study, there was no significant difference in terms
of eosinopenia between those who both recovered and had a mortal course
(14). Similarly, Lippi et al. reported that there was no difference in
eosinophil count between mortal and recovered patient groups. In
addition, they emphasised that the increase in eosinophil count was
similar in both groups throughout the course of the disease, and the
improvement in eosinopenia was not a prognostic factor in terms of the
course of the disease and mortality in COVID-19 infection (5). In
contrast, Liu et al. reported that eosinopenia is common in COVID-19
patients, but there was an increase in eosinophil count before
discharge, and this improvement in eosinophil count may be an indicator
of clinical improvement (8). In addition, Chen et al. reported that
eosinopenia seen at initial admission to the hospital improved in
patients who recovered but was maintained in patients with a severe
prognosis (15). At the same time, other studies have emphasised that
persistent eosinopenia during hospitalisation is associated with low
recovery rates, and improvement in eosinopenia may be an indicator of
improvement in clinical status (6, 16, 17). There are also various
studies emphasising that not only eosinophils but also basophil counts
are lower in those with a mortal course compared to recovered patients
(18, 19). Similarly, Sun et al. reported that COVID-19 patients with a
low basophil count and low basophil percentage in white blood cells may
have a more mortal course. In addition, they emphasised that both the
basophil count increased from the acute phase to the recovery phase and
that this increase showed a similar correlation with anti-CoV-2
immunoglobulin G (IgG) (20). Rodriquez et al. also reported that both
eosinophils and basophils play an effective role in immunopathology and
viral defence during acute COVID-19 infection, and eosinopenia and
basopenia developed in most patients. They emphasised that there was an
increase in eosinophil and basophil counts when they passed from the
acute period to the recovery period (11). It is similar to the findings
in our study. In addition, as the depth of eosinopenia and basopenia
increases, a significant deterioration is observed in the clinical
course of the patients. Cazzaniga et al. reported that oxygen saturation
was lower in patients with eosinopenia and basopenia, and these patients
needed more intensive care. In addition, they demonstrated that 4-week
mortality rates were high in these patients (21). Ajeneye et al.
reported that eosinopenia, along with lymphopenia, was an important
parameter in the diagnosis of COVID-19 and showed a strong correlation
with mortality (7). These results were supported in our study;
eosinopenia and basopenia had a similar relationship with mortality. In
other words, a significant decrease in eosinophil and basophil count can
be seen in COVID-19 patients due to the development of immune system
disorders.
CONCLUSİON
In our study, a significant decrease was observed in the count of
eosinophils and basophils in the mortal group of COVID-19 patients.
Eosinopenia and basopenia may be parameters that can be used to
facilitate the diagnosis of COVID-19, as the depth of both eosinopenia
and basopenia was positively correlated with COVID-19 mortality.
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