INTRODUCTION
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
outbreak that began in Wuhan, China, in December 2019 rapidly spread
worldwide, insofar as the World Health Organization has declared
COVID-19 to be a pandemic and a public health emergency of international
concern (1-4). Although the disease is typically associated with
respiratory tract involvement, the virus also can affect other systems
including hematological and cardiovascular systems through different
hypothesized mechanisms (5, 6). One of the most important underlying
mechanisms is an increased level of inflammatory mediators (7). This
inflammatory process is accompanied by thrombotic events, including
pulmonary thromboembolism (PTE), in COVID-19 patients (8-10).
Pulmonary thromboembolism is a cause of mortality among COVID-19
complications. While the case fatality rate for COVID-19 ranges from 2%
to 3%, the mortality rate for COVID-19 patients who develop PTE is
45.1% (11). This remarkable complication is reported in 15.3 percent of
COVID-19 cases (12). Due to the high mortality and incidence of PTE, as
well as the fact that prompt treatment is highly effective and has been
shown to significantly impact clinical outcomes, early diagnosis of PTE
is crucial (12, 13).
Nevertheless, PTE diagnosis in COVID-19 is challenging for a variety of
reasons. First, PTE and COVID-19 clinical manifestations may overlap
(14). Second, hospital overcrowding during the resurgence of the
COVID-19 epidemic, costs, and lack of availability in all centers make
chest CT angiography inaccessible for all patients with probable PTE
(15). Third, available clinical prediction models for PTE do not apply
to COVID-19 patients. Therefore, their use as the sole diagnostic
screening tool in clinical practice is not recommended. New clinical
probability models for PTE that have been validated in COVID-19 patients
are consequently required (16).
As previously stated, thrombotic events accompany the inflammatory
process in patients with COVID-19 (8-10). Notably, hematological ratios
are one of the valuable, inexpensive, and widely-examined markers of
inflammation (17). In addition, circulating biomarkers of inflammation,
such as Neutrophil-to-Lymphocyte ratio (NLR) and Platelet-to-Lymphocyte
ratio (PLR), have been proposed as reliable prognosticators for both
COVID-19 and PTE patients (18-20). Despite the importance of the
aforementioned hematologic markers, there are very few studies focusing
on the prediction of PTE occurrence or PTE severity in COVID-19 patients
with probable PTE, accordingly, we conducted an exploratory analysis to
evaluate the potential role of these parameters as predictors of
thromboembolism in COVID-19 patients and the correlation of CBC
parameters with the simplified-PESI score as an indicator of PTE
severity.
METHOD