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Table of Contents
Year : 2021  |  Volume : 18  |  Issue : 3  |  Page : 158-161

Leukocyte morphological changes in COVID-19, a peripheral smear study and analysis at a tertiary health care centre in India

Department of Hematology, Apollo Hospital, Chennai, Tamil Nadu, India

Date of Submission31-Mar-2021
Date of Decision12-Apr-2021
Date of Acceptance30-Apr-2021
Date of Web Publication02-Jul-2021

Correspondence Address:
Mamta Soni
Department of Haematology, Apollo Main Hospital, Chennai - 600 006, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/am.am_28_21

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Context: Coronavirus disease 2019 (COVID-19) as the name depicts, a contagious disease caused by the coronavirus that emerged in the year 2019 December, at the Wuhan province in China. The knowledge on the pathogenesis of the disease at the cellular level to correlate with the clinical severity is still evolving. Various clinicopathological features and nature of the disease were gradually identified from those who were affected by the disease. Apart from the clinical presentation, certain investigations played a major role in diagnosing and assessing the severity of the disease. Morphological impact on blood cells was also caused by the severe acute respiratory syndrome-CoV-2 virus. Aim: Morphological analysis of leukocytes on blood samples of COVID19 patients. Settings and Design: Peripheral smear study of blood samples of COVID19 patients admitted at our tertiary care center. Subjects and Methods: Microscopic peripheral smear examination of leukocyte morphology on study samples. Statistical Analysis Used: All the data were recorded and analyzed statistically using Ms-Excel. Results: Our study demonstrated certain acquired pathogenic abnormalities of the leukocytes, that are acquired neutrophilic nuclear projections (ANNP), plasmacytoid lymphocytes, acquired Pelger-Huet anomaly (APHA), myeloid left shift, neutrophils with toxic granules and cytoplasmic vacuoles, and apoptotic cells. Conclusion: To summarize, in our study we observed similar features that were recorded in few studies earlier, such as APHA and plasmacytoid lymphocytes in convincing percentages among the COVID-19 patients in our population. Adding to these ANNP was one more prominent feature we encountered in majority of COVID-19 cases.

Keywords: Acquired neutrophilic nuclear projections, acquired Pelger-Huet anomaly, coronavirus disease 2019, neutrophilic projections, plasmacytoid lymphocytes

How to cite this article:
Kannan G, Soni M. Leukocyte morphological changes in COVID-19, a peripheral smear study and analysis at a tertiary health care centre in India. Apollo Med 2021;18:158-61

How to cite this URL:
Kannan G, Soni M. Leukocyte morphological changes in COVID-19, a peripheral smear study and analysis at a tertiary health care centre in India. Apollo Med [serial online] 2021 [cited 2021 Dec 6];18:158-61. Available from: https://www.apollomedicine.org/text.asp?2021/18/3/158/320556

  Introduction Top

Coronavirus disease 2019 (COVID-19), an ongoing pandemic in, after nearly 10 years since the Swine Flu pandemic in 2009, is the present health emergency situation in the world.[1],[2] Since the novel coronavirus caused a severe acute respiratory distress it was named as severe acute respiratory syndrome (SARS)-COV-2.[1] Apart from the clinical presentation, certain investigations played a major role in diagnosing and assessing the severity of the disease. The immune-mediated inflammatory response plays an important role in the pathogenesis[3],[4] of COVID-19, as the severity of the disease progresses there is significant lymphopenia, eosinopenia, and neutrophilia.[5],[6],[7] A few studies have stated about the morphological impact caused by the SARS-CoV-2 virus infection on peripheral blood film of COVID-19 patients.[6],[8] Variants of lymphocytes and plasmacytoid lymphocytes[9],[10] were seen more often; morphologic abnormalities such as acquired Pelger-Huet anomaly (APHA) and left shift, were commonly significant in COVID-19 cases.[11],[10]

  Subjects and Methods Top

Information on the hemato-morphological changes in COVID-19 infection is little. In our study, we aimed to detect various morphological abnormalities demonstrated by the peripheral blood leukocytes in COVID-19 infection. Adult patients, who were diagnosed COVID-19 positive, were admitted in the hospital, and had complete blood counts done, were included in the study, which comprised a total of 127 cases. For the study, blood smears were prepared manually from Ethylenediaminetetraacetic acid blood samples that were collected for complete blood count, stained with Leishman stain using semi-automated slide stainer, by qualified technical personnel.

The slides were viewed in ×10, ×40, and ×100 magnifications. For morphological details, minimum of 100 leukocytes are viewed under ×100 to ascertain changes in leukocytes along with red blood cells (RBCs), platelets, nucleated RBCs, and abnormal cells. Each morphologic variant and abnormality was noted down and graded in percentage.

  Results Top

[Table 1] shows the incidence of each morphological abnormal pattern observed in leukocytes of COVID-19 patients in our study. The total number of cases in our study comprised 127.
Table 1: Incidence of morphological patterns of leucocytes in COVID-19

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In our study, few neutrophils in certain cases demonstrated a slender or curved, angulated, single or multiple, and sometimes thorn-like, raised from the nucleoplasm of the neutrophil nucleus into its cytoplasm [Figure 1]a and [Figure 1]b, which we termed as acquired neutrophilic nuclear projections (ANNP) and it was identified in smears of 90 (70.9%) patients which included 11 female patients too. Among the 90 patients whose blood smears demonstrated ANNP, smears of 22 (24.5%) patients demonstrated ANNP with an average of 9.3 neutrophils/polymorphs per 100 cells and they did not receive any steroid or antiviral therapy prior to sample collection, during the course of treatment in our hospital; while the smears of remaining 68 (75.5%) patients demonstrated ANNP with an average of 11.8 neutrophils/polymorphs per 100 cells, blood samples of these patients were collected while they were receiving steroidal and antiviral treatment in our hospital. We have also recorded ANNP in one patient nearly 100 days post COVID-19 infection; on a routine follow-up examination, with no history of steroidal or antiviral therapy.
Figure 1: (a) A neutrophil showing acquired angulated nuclear projection. (b) High-power field showing multiple neutrophils with acquired angulated nuclear projections. (c) Bi-lobed neutrophils at high power (×40), showing acquired Pelger-Huet anoma

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Bilobed and monolobated neutrophils [Figure 1]c that are identified as APHA. It was observed in the smears of 62 (48.9%) patients; among them, 52 (40.9%) demonstrated APHA on an average of five percent of its neutrophils, whereas the remaining eight (6.2%) demonstrated an average of 14% APHA.

Apoptotic cells [Figure 2]a and [Figure 2]b were seen in smears of 37 (29.2%) patients, ranging from one to five percent. Toxic granulation [Figure 2]c was also seen in neutrophils of 44 (34.7%) patients infected with COVID-19 in our study; ten among them had >ten percent of neutrophils demonstrating this feature. Plasmacytoid lymphocytes [Figure 3]a was prominent in 44 (34.7%) patients. Activated monocytes [Figure 3]b with multiple vacuoles were commonly noted; also nucleated red cells [Figure 3]c were commonly encountered being associated with myeloid left shift [Figure 3]d in patients with severe form of COVID19 infection.
Figure 2: (a) Apoptotic cell in oil immersion (×100), showing liquefied chromatin (b) Apoptotic cell showing condensed nucleus with fragmentation in a pinkishblue cytoplasm, (c) Toxic granulation of neutrophil

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Figure 3: (a) Plasmacytoid lymphocyte, showing a deep blue cytoplasm with eccentric nucleus, (b) Activated monocyte, showing a dense cytoplasm with multiple vacuoles, (c) Nucleated red blood cell,(d) Myeloid precursors

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  Discussion Top

Earlier in this pandemic, APHA in COVID19 patients were reported by Zini et al.,[12] while Nazarullah et al.[11] gave a quantified report on the similar feature. This finding in our study strongly supports that PelgerHuet anomaly is an acquired morphologic feature of the neutrophils that are infected by the SARS-CoV-2 virus in COVID-19 disease; although the hypothesis of this mutagenic morphology is unclear.

Apoptotic leukocytes though well-known are rare to occur in peripheral blood film, this was commonly encountered in smears of patients with moderate-to-severe forms of COVID19 infection. Similar features were also recorded by Zini et al.[12] in COVID19 infection.

ANNP/pseudo nuclear projections are sought to be different from the sex-specific projections termed “Barr bodies” or “drumsticks”[13] as they are oriented to females, while ANNP was recorded in both the sexes; also morphologically they are not identical. According to a study done by Méhes.[14] on neutrophilic nuclear projections, Barr bodies or drumsticks belonged to category A in their study, which they found to be appearing more common in females denoting it as female sex specific, whereas those similar to ANNP belonged to category C which as per their study did not lean toward sex specificity, they were said to be more common among patients on steroidal therapy steroid. It is also not similar to those which were described to be present in certain genetic abnormalities such as Trisomy 13,[15] Trisomy 18 (Edward syndrome),[16] as life span in such patients is usually not more than a year, while those in our study belonged to the adult or older age group and neither did the both the groups have any history of a genetic disease or syndrome. ANNP were initially noted in few random cases of COVID-19 which we came through during our routine peripheral smear examination, the percentage of neutrophils bearing the nuclear projections significantly increased among COVID-19 patients who underwent in-patient treatment during the course of the disease. Earlier, in a study, it has been stated that few patients after receiving androgen therapy[14],[17] developed neutrophilic nuclear projections. Hence, it is assumed that ANNP is an acquired morphological abnormality that is developed in majority of COVID-19 patients who require hospitalization; while the physiological or pathological behavior of ANNP is unknown. To add upon, steroid therapy augments ANNP as the average that was demonstrated in patients who received steroid therapy was high. Furthermore, a post COVID19 on follow-up continued to demonstrate ANNP, this shows that COVID-19 patients may tend to carry this particular abnormality, although they have recovered from the disease. Hence, an in-depth study is further required in this aspect to find that if there could be any chromosomal mutagenic change due to neutrophil activation[18] in COVID-19 disease.

Neutrophils with toxic granulation[19] and myeloid precursors (myeloid left shift)[12] were much recorded in patients with critical clinical outcome, as they developed associated secondary sepsis added to COVID-19 pneumonia.

Lymphopenia was present in the majority of the cases; circulating plasmacytoid lymphocyte is one of the common lymphocytic morphological abnormality encountered in COVID19 infection, also represented by Sadigh et al.,[19],[10] Furthermore nucleated RBCs,[20] vacuolated monocytes[20],[8] were other morphologic abnormalities that we noted commonly in COVID19 patients who had a clinically severe course of the disease.

To summarize in our study, we observed similar features that were recorded in a few studies earlier in COVID-19 patients, such as APHA, apoptotic cells, toxic granulation, myeloid left shift, and plasmacytoid lymphocytes in convincing percentages in our population. Adding to this ANNP was one more prominent feature we encountered in majority of COVID19 cases, while its pathogenic hypothesis is yet to be understood.

  Conclusion Top

In agreement with the published studies, morphological changes in leucocytes such as APHA (Acquired Pelger Huet Anomaly), apoptotic cells, toxic granulation, myeloid left shift, and plasmacytoid lymphocytes were significantly observed among Covid19 patients. In addition, ANNP (Acquired Neutrophilic Nuclear Projections) was one more prominent feature observed in majority of COVID-19 patients.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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Sadigh S, Massoth LR, Christensen BB, Stefely JA, Keefe J, Sohani AR. Peripheral blood morphologic findings in patients with COVID-19. Int J Lab Hematol 2020;42:e248-51.  Back to cited text no. 10
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Zini G, Bellesi S, Ramundo F, d'Onofrio G. Morphological anomalies of circulating blood cells in COVID-19. Am J Hematol 2020;95:870-2.  Back to cited text no. 12
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Kahwash BM. Case reports in hematology. In: Case Report Aberrant (Barbed-Wire) Nuclear Projections of Neutrophils in Trisomy 18 (Edwards Syndrome). S.L: Hindawi; 2015. p. 1-4.  Back to cited text no. 16
Lee S, Khankhanian P, Mascarenhas JO. Corticosteroid-induced morphological changes in cells of the myeloid lineage. Am J Hematol 2015;90:679-80.  Back to cited text no. 17
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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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