Discussion
In suspicious cases of Covid-19 PCR is used in the diagnosis and is the
gold standard, in some patients suspicious of having pneumonia may have
to undergo a CT scanning. Yet PCR and CT both are not availbale in every
healtcare institution. Therefore, there is a need for simpler and more
practical methods to detect Covid-19 cases and else more Covid-19
patients with pneumonia which may have to be internated or carefully
followed.
Our study demonstrated that neutrophil levels decrease in Covid-19
patienets with and without pneumonia compared to healthy subjects (p
<0.001 for both comparisons). The data on neutrophil levels in
Covid-19 are incomplete and have not been widely studied. The available
data suggest that neutrophilia is an expression of the cytokine storm
and hyperinflammatory state which have an important pathogenetic role in
COVID-19 and related infections. In previous studies neutrophilia is
reported in patients treated in intensive care unit 5.
Yet neutrophil levels may be effected by many secondary diseases. In our
study we included previously totally healthy patients at admission
before using any kind of medicine. In a study Gumus et al. demonstrated
low neutrophil levels in pediatric Covid-19 patients6. Similar to our study Xie et al. reported low levels
of neutrophils in Covid-19 patients 7 yet their study
contained patients who had chnronic diseases like asthma, chronic
obstructive pulmonry disease, coronary heart disease etc.
Lymphocytes play an important role in the maintenance of immune system
function. After a viral infection, changes in total lymphocyte numbers
varies with different virus types. Wang et al. reported decreased
lymphocyte levels in patients with Covid-19 8. Similar
to their study we found low lymphocyte levels in patients with Covid-19
pneumonia. Eventhough low lymphocyte levels have been demontrated
previously our study demonstrated that lymphocyte levels decrease in
preiously healthy Covid-19 patients but no statistically difference
between those with and without pneumonia.
Monocytes and macrophages are the most enriched immune cell types in the
lungs of Covid-19 patients and appear to have a central role in the
pathogenicity of the disease 9. Current data suggest a
preponderant role for monocyte-macrophage activation in the development
of immunopathology of Covid-19 patients 10.In our
study we found lowe monocyte levels in Covid-19 patients with pneumonia
compared to healthy controls (p <0.001) and patients without
pneumonia (p <0.001). Zhang et al observed that during
SARS-CoV-2 infection, there are morphological and inflammation-related
phenotypic changes in peripheral blood monocytes that correlate with the
patient’s outcome 11. Zhang et al. did not detect
significant differences in the number of monocytes between patients with
Covid-19 and normal healthy individuals. In a study Kos et al. reported
reduced rate of activated monocytes mainly observed in patients with
severe Covid-1912. Eventhough our study demonstrated
that monocyte levels decrease in previously healthy Covid-19 pneumonia
and in those without these results reflect begining of the disease
before treatment. Levels may differ after progression of the disease and
may be effected by drugs used in treatment.
Eosinophils are circulating and tissue-resident leukocytes that have
potential of proinflammatory effects in some diseases. Eosinophils also
have been shown to have various other functions like immunoregulation
and antiviral activity. Yet their role in Covid-19 is not well known.
Previosly it has been reported that Covid-19 patients had a decrease in
circulating eosinophil counts, which was significantly more frequent
than other types of pneumonia patients 7. Zhang et al.
has previously reported eosinopenia in patients with acute respiratory
deterioration during infection with SARS-CoV-213.
Zhanh et al. included 140 Covid-19 patients with comorbidities which may
effect eosinophil levels yet similar to their study we also found low
levels of circulating eosinophils in patients with Covid-19. Our study
demonstrated that circulating eosinophil counts decrease in preivously
totally healthy patients with Covid-19 and much more in Covid-19
patients with pneumonia. These results may indicate involvement of the
lungs is associated with decrease in eosinophil levels. So a treatment
strategy which increases eosinophil levels or targeting reasons of
eosinopenia may help in dealing with Covid-19.
Covid-19 causes a spectrum of disease; some patients develop a severe
proinflammatory state which can be associated with a unique coagulopathy
and procoagulant endothelial phenotype. We found Covid-19 patients with
pneumonia had the lowest platelet counts. Trombocytopenia is a big
problem during Covid-19 because many patients need anticoagulant
prophylaxy which implies that thrombocytopenia needs to be attached more
importance in the follow-up of Covid-19 patients. The difficulty is to
choose the apropriate anticoagulant while on the other side there is
trombocytopneia.
Prveiosly it has been reported that increased MPV levels was associated
with mortality in Covid-19 patients 14. In another
study Ozcelik et al. compared Covid-19 patients with influenza pneumonia
and reported low MPV levels in patients with Covid-1915. MPV levels also found significantly high in
asymptomatic children infected with Covid-19 6. In
this study we found no difference in MPV levels between groups. MPV can
be effected from many diseases and conditions and the teqnique used
which may effect the results. In this study similar to MPV levels we
didnt find statistically differences between PDW and RDW levels. In a
study Henry et al. found a progressive increase of RDW with advancing
Covid-19 severity 16. The discrepency between two
studies might be due to patients grops, Henry et al. included patients
with comorbidities yet we aimed to see if RDW can be usefull in the
early diagnosis of previously healthy Covid-19 patients.
In recent years, some ratios have been in use by researchers in the
diagnosis and prognosis of many inflammatory conditions. Some of these
are neutrophil/lymphocyte, platelet/lymphocyte, and monocyte/lymphocyte
ratio. In a study Seyit et al. Reported high NLR in patients tested
positive for SARS-CoV-2 compared to controls 17. In
our study we found no differences between NLR of three groups. In a
study from Wuhan/China Yang et al. reported elevated NLR significantly
associated with illness severity 18. Difference
between our study and the study conducted by Seyit et al. migt be due to
patient characteristics or to the heterogenisity of Covid-19. Seyit et
al found high levels of PLR in patients with Covid-19. In acoordance
with their study we also found high levels of PLR in patients with
Covid-19 pneumonia compared to healthy subjects (p <0.013) and
Covid-19 patients without pneumonia compared to healthy controls (p
<0.005). Our study demonstrated that PLR is high in Covid-19
patients but it might not be associated with disease severity at least
at the begining stage of the disease. Yang et al. investigated 93
Covid-19 patients and found out that lyphocyte to monocyte ratio (LMR)
levels of severe patients were significantly higher than those of
non-severe patients.18. In our study we aimed to
observe if MLR could be used in the diagnosis of Covid-19 patients at
the admmision before undergoing treatment. We found highest MLR in
patients without Covid-19 pneumonia versus patients with pneumonia and
healthy controls (both p <0.001). More studies are needed to
obtain more detailed information.