Discussion
This research aims to inquire about the association between lymphopenia
and lung involvement in the outcome of hospitalized patients with
COVID-19. Here, the lymphocyte percentage was calculated as 20.35
±10.16, it was significantly associated with more severe lung
involvement (P= 0.00). The lymphopenia was observed in 312 patients
(52.3%) and 284 patients lied within the normal range. Of the 596
hospitalized patients, 84 (14%) died and 515 cases were discharged. We
observed that CRP and ESR may not a predictable inflammation marker in
patients with COVID-19. Of the 596 patients, 260 (43.6%) showed
bilateral ground‐glass and consolidative opacities, 253 (42.4%) had
bilateral ground-glass opacities, and 50 (8.4%) had bilateral
consolidation on chest CT. While the pleural effusion, consolidation,
GGO was seen in COVID-19 cases, 24 patients (4.1%) had exclusively
unilateral lung involvement. The bilateral ground-glass opacities and
consolidation were the major pulmonary CT findings of COVID-19 patients.
In the same conclusion as ours, other studies reported lymphopenia as a
reliable indicator for COVID-19 severity. Tan et al were shown
that there is a reverse association between lymphocyte count and
COVID-19 severity and its prognosis 14. The lymphocyte
count < 20% was reported in severe clinical illness;
lymphopenia at the level <5% was found in patients who died14. In another study, lymphopenia at the level of 40%
was demonstrated within 191 patients 26. It was also
presented that 48% of included patients experienced underlying
non-communicable diseases including hypertension, diabetes, and coronary
heart disease 26. Several symptoms of coronavirus
infection were also described in Iranian children and were defined as a
less serious disease with a good prognosis 27. Zhenget al compared the laboratory features of COVID-19 pneumonia to
non- COVID-19 pneumonia. They stated that COVID-19 pneumonia- derived
lymphopenia negatively affect the biochemical indicators of organ
dysfunction 28. A study done on 221 hospitalized
COVID-19 patients confirmed leukopenia (33%), lymphopenia (73.8%), and
more susceptibility to fungal and bacterial infections29. Chinese research explained that bilateral
pneumonia, shorter duration of onset to admission, lymphopenia, and
disease severity are regarding as risk factors of prolonged
hospitalization of COVID-19 30. Lymphopenia may occur
along with an increased level of cytokine, disease severity, mortality,
and impaired immune response 31.
Tan et al showed the inverse relationship between lymphocyte
count and disease severity and its prognosis in 92 COVID-19 patients32. It was disclosed that LYM% lower than 20% was
seen in severe cases and it fell under 5% in dead patients32. Comparison of laboratory variations of 88 patients
with COVID-19 pneumonia and 22 non-COVID-19 pneumonia cases revealed
that lymphocyte depletion, not neutrophil, and monocyte, inversely
affect biochemistry disorder and organ failure 33.
Lymphopenia and augmentation of cytokine are accompanied by increased
disease severity, death, and disrupted immune response31. Despite that some studies found higher levels of
ESR and CRP as inflammatory indicators in severe patients of COVID-1934-36, our results did not show increased ESR and CRP
levels in severe cases. It was also shown by Peng et al37.
The chest CT scan plays a crucial role in the early diagnosis and
evaluation of patients with COVID-19 pneumonia likewise, lymphopenia and
thrombocytopenia were the verified markers for disease detection38. The sensitivity of a chest CT imaging was examined
among 1014 patients who had negative RT-PCR 19. Their
results showed high sensitivity of lung CT (75% of the included
population were positive for COVID-19) and suggested it as a reliable
detection method in epidemic regions 19. Subgroup
analysis revealed that COVID-19 patients with severe pulmonary lung
involvement and lymphopenia had 9.2-fold increased odds of in-hospital
mortality. The mortality rate was also calculated in patients with
severe lung involvement and patients with lymphopenia, these groups had
a mortality rate of 3.4 and 3.6 times greater than those without lung
involvement and lymphopenia (Table 3). In other words, the mortality in
the case of lymphopenia along with severe lung involvement was deeply
different compared with patients with neither lymphopenia nor lung
involvement (OR 9.2, [95% CI 4.3- 19.7]) (Table 3). We found that
the incremental effect of lymphocyte count and lung involvement tracks
the multiplicative model, no additive model.
Assessment of RT-PCR positive COVID-19 cases showed leukopenia,
lymphopenia, and high CRP concentration as hematological and biochemical
parameters. The most involved segments were lung segments 6 and 8 with
peripheral pulmonary localized lesions 39. The
sensitivity of the CT scan was inspected in mild COVID-19 reach to a
high level after 10 days of infection 40. It was
examined that the most frequent CT Manifestations and Clinical
Features were GGO (86%) and consolidation (62%) 41.
Similarly, we found that bilateral distribution of GGO and consolidation
are the main pulmonary lesions of COVID-19 patients.
The inflammatory marker of platelet to lymphocyte ratio (PLR) was
suggested as a predictive indicator for disease severity and mortality
in infectious disease and cancer 42,43. Rong et
al noted the value of PLR for predicting the clinical outcome of
COVID-19 and patients’ observing. They found out a high PLR is
associated with more severity and longer hospitalization44. Conversely, our study showed no significance and
it was not correlated to mortality (p= 0.16). The PLR was not correlated
with the LOS (p= 0.06; r= 0.07). Notably, we found that LOS in patients
with lymphopenia and severe lung involvement was remarkably higher than
others (p <0.05). Likewise, a Chinese study represented that
bilateral pneumonia in a lung CT scan, a short period from symptoms
onset to hospitalization, lymphopenia, and disease severity were the
main factors in prolonged LOS (ProLOS) 45.