|
 
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| REVIEW ARTICLE |
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| Year : 2022 | Volume
: 10
| Issue : 3 | Page : 124-126 |
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Peripheral blood smear findings in COVID infection - A review article
Gunvanti B Rathod1, Pragnesh B Parmar2, Rashmi Kundapur3
1 Department of Pathology and Lab Medicine, All India Institute of Medical Sciences, Hyderabad, Telangana, India
2 Department of Forensic Medicine and Toxicology, All India Institute of Medical Sciences, Hyderabad, Telangana, India
3 Department of Community and Family Medicine, All India Institute of Medical Sciences, Hyderabad, Telangana, India
| Date of Submission | 07-Jun-2021 |
| Date of Decision | 09-Jun-2021 |
| Date of Acceptance | 19-Jul-2021 |
| Date of Web Publication | 21-Feb-2023 |
Correspondence Address:
Pragnesh B Parmar
Department of Forensic Medicine and Toxicology, All India Institute of Medical Sciences, Bibinagar, Hyderabad, Telangana
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/DYPJ.DYPJ_31_21
Coronavirus disease-2019 (COVID-19) infection caused worldwide morbidity and mortality with complications and still, it is going on. After the Spanish flu, no other illness has obtained such a heavy toll on the human population such as the severe acute respiratory syndrome coronavirus 2. The most common symptoms of COVID-19 infection were fever, cough, dyspnea, expectoration, headache, myalgia, or fatigue and gastrointestinal symptoms. Complete blood count parameters with morphological findings can help a pathologist to alert the physician of future disease progression. Collective findings of various articles were noted down and crux of it was presented here. Lymphocytopenia, neutrophilia, eosinopenia were the common findings with morphological abnormality in lymphocytes and neutrophils in COVID-19 infection. To reach a definite conclusion regarding the specificity and the reliability of these viral cytopathic effects in the peripheral smear, more research is required in this field. Keywords: Coronavirus disease-2019 infection, morphological abnormality, peripheral blood smear findings, worldwide morbidity
How to cite this article:
Rathod GB, Parmar PB, Kundapur R. Peripheral blood smear findings in COVID infection - A review article. D Y Patil J Health Sci 2022;10:124-6 |
In Wuhan, City of China, a new type of viral infection has emerged in December, 2019. Its initial genomic sequencing data does not match with previously sequenced coronavirus (CoV), suggesting a novel CoV strain (2019-nCoV), which has now been termed as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). As we all know coronavirus disease-2019 (COVID-19) is suspected to originate from an animal host followed by human-to-human transmission. COVID-19 infection has been a cause of concern and disruption globally in 2020. The COVID-19 infection had spread rapidly throughout the whole country of China and subsequently to other countries. Due to the severity of this outbreak and the potential of spreading on an international scale, the WHO declared a “global health emergency” on January 31, 2020. Later, a pandemic situation was also declared on March 11, 2020. It has spread worldwide and caused worldwide morbidity and mortality with complications. After the Spanish flu, no other illness has taken such a heavy toll on the human population such as the SARS-CoV-2.
The most common symptoms of COVID-19 infection were fever, cough, dyspnea, expectoration, headache, myalgia, or fatigue, and gastrointestinal symptoms. Few less common signs are also noted such as diarrhea, hemoptysis, and shortness of breath.[1] Recently, individuals with asymptomatic infections were also suspected of potentially transmitting infections, which further add to the complexity of disease transmission dynamics in COVID-19 infections.[2] RNA tests can confirm the diagnosis of SARS-CoV-2 cases (COVID-19) with real-time reverse transcription-polymerase chain reaction (RT-PCR) or next-generation sequencing.[3],[4] In the present scenario, nucleic acid detection techniques such as RT-PCR are considered the method of choice for confirming the diagnosis in clinical cases of COVID-19.[3]
The best sample for testing is lower respiratory tract sampling such as bronchoalveolar lavage fluid. It is more sensitive than the throat swab due to its higher positive rate of the nucleic acid test.[3] At present, the diagnosis of COVID-19 is done using upper respiratory tract specimens collected using nasopharyngeal and oropharyngeal swabs. However, tremendous risk is associated with this technique to health care workers because of close contact with patients.[5]
For the diagnosis, treatment, and prognosis of COVID-19 patient’s clinical laboratory has played a decisive role. The most common findings in the blood samples of COVID-19 infected patients are anemia, lymphocytopenia, increased C-reactive protein, erythrocyte sedimentation rate, lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, and D-dimer.[6]
As we all know, complete blood counts (CBCs) with peripheral blood smear (PBS) examination have been recommended as essential tools for patient monitoring in each and every disease. CBC parameters with morphological findings can help a pathologist to alert the physician of future disease progression. Here, we had reviewed the PBS findings of patients with COVID-19 infection.
Guan, et al. provided data on the clinical characteristics of 1099 COVID-19 cases with laboratory confirmation during the first 2months of the epidemic in China.[7] According to their data, the majority of patients presented with lymphocytopenia (83.2%). According to various literatures, the association between lymphopenia and poor prognosis is proved. Huang, et al., and Wang, et al.[8],[9] highlighted an association between lymphopenia and the need of intensive care unit care, whereas Wu, et al.[10] showed an association between lymphopenia and acute respiratory distress syndrome development. Death rate was more in patients with increased neutrophil count. In Washington, USA critically ill patients with COVID-19 showed prominent lymphopenia.[11],[12] This is the reason why serial assessment of lymphocyte count dynamics may be predictive of patient outcome.
In a case report from Singh, et al.[13] noticed the common hematological findings on CBC are lymphocytopenia, neutrophilia, eosinopenia, and mild cytopenia. They also examined some unusual findings in the neutrophils which were never seen in any other infection. In their case report, neutrophils showed heavily clumped chromatin with toxic granules and cytoplasmic vacuoles. There was also the presence of nuclear detachment with elongated nucleoplasm and ring-shaped nuclei with platelet surface attachment. C-shaped, fetus-like nuclei were also noted by them with aberrant nuclear projections. Ahnach, et al.[14] from Morocco had examined PBS of 146 patients with COVID-19 as of May 16, 2020. They also noticed a neutrophil granulocyte with dysmorphic morphology marked by hypogranular cytoplasm and hyposegmented nucleus. Berber, et al.[15] noticed decreased number of segmented neutrophils and eosinophils with pyknotic neutrophils and increased Pseudo-Pelger-Huet anomaly.
Regarding lymphocyte series, they noticed large granular lymphocytes with round to indented nuclei, condensed chromatin, and prominent nucleoli in a few, along with abundant pale blue cytoplasm with distinct variably sized azurophilic granules. They also observed cytoplasmic pod formation and apoptosis in a few lymphocytes. The nuclei were large, having fine chromatin with nuclear blebbing and nuclear overlapping by vacuoles was also observed in some of the lymphocytes. Similar findings were also noticed by Ahnach, et al.[14] in the form of rarely activated lymphocytes and large monocytes. In the original research article by Berber, et al. showed that increased Pseudo-Pelger-Huet anomaly/mature lymphocyte rate was associated with a severe stage disease, whereas high initial mature lymphocyte and monocytes with vacuoles rates at the time of diagnosis may be an indicator of shortened duration of hospitalization. In the pilot study by Liu, et al.[16] showed atypical lymphocytes with irregular shape with excessive cytoplasm but normal nucleus. They had also observed plasmacytoid lymphocytes.
The platelet count was adequate and morphology was normal except with a few giant form sand focal platelet attachment on the surface of all types of leukocytes.[13] Ahnach, et al.[14] also showed frequent anomalies in platelet morphology, mainly consisting of giant platelets of different sizes.
By reviewing the PBS findings collectively, we can say that lymphocytopenia, neutrophilia, eosinopenia were the common findings with morphological abnormality in lymphocytes and neutrophils. Lymphocytopenia is associated with poor prognosis. A close examination of peripheral smear can give us ideas about the ongoing pathogenesis of the disease and whether the presence of hemophagocytosis, toxic granules such as granules, or vacuoles in white blood cells can become indicators of adverse clinical outcome. Increased Pseudo-Pelger-Huet anomaly/mature lymphocyte rate suggests a severe stage disease, whereas high initial mature lymphocyte and monocytes with vacuoles rates at the time of diagnosis may be an indicator of shortened duration of hospitalization. In all studies, the authors agreed that preliminary results remain limited for the hematological findings in COVID infections and more investigation is required to study the reversibility of these abnormalities and their impact on severity.
| Conclusion | |  |
At present, PBS is an inexpensive, easily performed, and rapid test in hematology laboratory. Compared to all inflammatory biomarkers, observation of blood cells can be a simple alternative for the first triage and early identification of the infection. Understanding of the hematological manifestations of SARS-CoV-2 is still in the evolving stage. To reach a definite conclusion regarding the specificity and reliability of these viral cytopathic effects in the peripheral smear, more research is required in this field.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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