Asian Journal of Transfusion Science
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LETTER TO THE EDITOR Table of Contents   
Year : 2022  |  Volume : 16  |  Issue : 1  |  Page : 152-153
Antihuman globulin test reactivity in SARS-CoV-2 infection-positive patients

Department of Transfusion Medicine, KEM Hospital, Mumbai, Maharashtra, India

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Date of Submission20-Nov-2021
Date of Decision18-Jan-2022
Date of Acceptance23-Jan-2022
Date of Web Publication30-Jul-2022

How to cite this article:
Thakkar S, Bhagwat S, Sharma J. Antihuman globulin test reactivity in SARS-CoV-2 infection-positive patients. Asian J Transfus Sci 2022;16:152-3

How to cite this URL:
Thakkar S, Bhagwat S, Sharma J. Antihuman globulin test reactivity in SARS-CoV-2 infection-positive patients. Asian J Transfus Sci [serial online] 2022 [cited 2022 Oct 2];16:152-3. Available from:


There is a paucity of published data on the simultaneous onset of SARS-CoV-2 infection and autoimmune hemolytic anemia (AIHA).[1] Hence, a prospective study of 55 blood samples of patients diagnosed with COVID-19 infection (detected by Reverse Transcription Polymerase Chain Reaction) was undertaken and tested for antihuman globulin (AHG) reactivity at the blood center of a tertiary care hospital in Western India. These samples were sent from wards to the blood center for pretransfusion testing and/or ABO and Rh typing. The study was conducted over a period of 6 months, from April 2020 to December 2020. All patients were hospitalized and were undergoing treatment with multiple drugs, including corticosteroids, antivirals, antibiotics, vasopressors, and were on invasive or noninvasive ventilation. None of them received COVID-19 convalescent plasma treatment.

At the blood center, direct antiglobulin test (DAT) and indirect antiglobulin test were done using the Column agglutination technology (Matrix AHG Coombs) test card, Tulip Diagnostic (Pvt. Ltd System, Goa, India). DAT was performed using C3D + immunoglobulin G (IgG) AHG Coombs Gel card. Auto control was put at all three temperatures that is immediate spin (IS), 4°C, and AHG phase. Out of the 55 patients, 51 (92.72%) of the samples were DAT positive. [Figure 1]
Figure 1: DAT positivity

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Out of the 55 patients, 35 (63%) were male and 20 (37%) were female. Twenty-four (44%) were group B, 14 (25%) were group A, 13 (24%) were group O, and 4 (7%) were group AB [Figure 2]. None of the patients had a positive antibody screen.
Figure 2: Percentage of Blood Group

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Autocontrol was positive in 37 (67%) patients, but no hemolysis was found in this group. Seven (14%) patients were autocontrol positive with hemolysis. However, 7 (14%) samples were DAT positive, but autocontrol was negative in them. [Figure 3]
Figure 3: Distribution of blood samples according to DAT and hemolysis

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The DAT detects immunoglobulin or complement bound, in vivo, to red blood cells (RBC), and is widely used to diagnose immune-mediated hemolytic anemias. Positive DAT results, with or without clinically evident anemia, have been reported in a subset of patients with various viral infections.[2] A positive DAT with the absence of hemolysis can occur in exogenous immunoglobulin administration, recent hemopoietic stem cell transplant, recent history of solid organ transplant, SLE, infectious mononucleosis, and some hematologic diseases and lymphoproliferative diseases. In these disease conditions, dysregulation of the immune system or a generalized inflammatory state leads to nonspecific adsorption of antibodies to the erythrocyte membrane. These IgG molecules are not immunologically bound to the erythrocyte membrane (i.e., they do not recognize and bind to specific erythrocyte antigens) and do not usually cause hemolysis. An eluate prepared from DAT-positive erythrocytes can determine whether the antibodies were immunologically or nonspecifically attached to these cells.[3]

These data suggest that the mechanism underlying DAT reactivity involves modifications of the erythrocyte surface during the course of the disease. A possible interpretation is that hyperinflammation in COVID-19 enhances the deposition of complement C3 and the binding of IgG autoantibodies to RBC membranes, which promotes the clearance of damaged RBC by macrophages.[4]

Positive DAT in the absence of signs of immune hemolysis is relatively common. In such cases, the interpretation of a positive DAT remains largely speculative on the serological side. If the affected patient does not have signs of hemolytic anemia, the positivity observed may be related to a number of in vivo occurrences that may result in an IgG- and/or C3d-positive DAT. As RBC membrane is negatively charged and IgG molecules are positively charged, these cells are susceptible to unspecific IgG attachment onto their surfaces, leading to an IgG positive DAT.[5] Finally, the high rate of DAT reactivity can have an impact on pretransfusion testing, as membrane-bound autoantibodies may mask the concomitant presence of RBC alloantibodies in patients that have been recently transfused and may complicate or delay the selection of phenotypically matched blood units.[6]

To conclude, anti-RBC antibodies were detectable in almost 90% of the patients with COVID-19 referred to our blood center. The serologic features of DAT reactivity in COVID-19 patients are different from those generally observed in AIHA. From the transfusion perspective, it is important for serology laboratory to be aware of this finding so that for patients who are SARS-CoV-2 positive and DAT positive but have a negative antibody screen and no clinical features of hemolysis, further serologic testing is not required. This will reduce unnecessary staff exposure to infected blood samples.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Lopez C, Kim J, Pandey A, Huang T, DeLoughery T. Simultaneous onset of COVID-19 and autoimmune haemolytic anaemia. Br J Haematol 2020;190:31-2.  Back to cited text no. 1
Parker V, Tormey C. The direct antiglobulin test: Indications, interpretation, and pitfalls. Arch Pathol Lab Med 2017;141:305-10.  Back to cited text no. 2
Zarandona JM, Yazer MH. The role of the Coombs test in evaluating hemolysis in adults. CMAJ 2006;174:305-7.  Back to cited text no. 3
Straat M, van Bruggen R, de Korte D, Juffermans NP. Red blood cell clearance in inflammation. Transfus Med Hemother 2012;39:353-61.  Back to cited text no. 4
Salama A. Clinically and/or serologically misleading findings surrounding immune haemolytic anaemias. Transfus Med Hemother 2015;42:311-5.  Back to cited text no. 5
Branch DR, Petz LD. Detecting alloantibodies in patients with autoantibodies. Transfusion 1999;39:6-10.  Back to cited text no. 6

Correspondence Address:
Sheenam Thakkar
Department of Transfusion Medicine, KEM Hospital, Parel, Mumbai - 400 012, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ajts.ajts_168_21

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  [Figure 1], [Figure 2], [Figure 3]



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2006 - Asian Journal of Transfusion Science | Published by Wolters Kluwer - Medknow
Online since 10th November, 2006