ABSTRACT
Background: The Direct Antiglobulin Test (DAT) is performed by testing the patient's red cells with poly or monospecific Anti Human Globulin (AHG) to demonstrate the in vivo link of red blood cells with antibodies and/or complement. The positive result of this test is usually due to the reaction of AHG with autoantibodies, alloantibodies (maternal or post transfusion) reactive against antigens present on the red cells, drugs that fix on the erythrocyte membrane (penicillin) or that alter it (cephalosporins), proteins often associated with hypergammaglobulinemia or I.V. infusion of immunoglobulins, complement fixation on red cells (from allo-autoAb, bacterial infections, drugs). Aims: The objective of this study is to understand if the positive result at DAT, in terms of frequency and specificity, has changed after the Covid 19 pandemic, and investigate the possible causes. Methods: We analysed the positive result of DAT performed on red cells of adult patients admitted to the wards of Asl Rome 1 and the affiliated clinics through the use of polypecific and monospecific sera (IgG, IgM, IgA, C3d, C3c) analysed using the IH 1000 System-Biorad Lab. All examinations performed was divided into two groups: those taken from 20/02/2018 to 20/02/2020 and from 21/02/2020 until 20/02/2022, representing the 2 years anniversary of the discovery of patient 1 in Italy. Results: In the first group of 101 patients who tested positive for DAT, 98% of them had positive results to IgG, while only the remaining 2% had positive results to the C3d isolated or associated with IgG. In the second group of 179 patients the positive results to IgG was 82% and the remaining 18% to C3d in isolation or in combination with IgG and C3c. We can observe how in the second group the overall positive results increased of about 80% and also the relative positive results to the C3d/C3c complement portion. It is also interesting to note that the positive results of only half of the second group (last 14 months in the period 2021-2022) are numerically about 50% higher than the previous year and 20% higher than the entire first group analysed (24 months). Summary/Conclusions: This increase in DAT positive results occurred in the second group, in particular in the last 14 months of the pandemic, could reflect the high levels of circulating immunoglobulins in the subjects analysed due to the endemic circulation of Sars Cov 2 virus and mass vaccination. These, according to our hypothesis, could have contributed to the outcome of positive results through a 'iatrogenic hypergammaglobulinemia' due to the high post vaccination titre and the immune response due to the increased circulation of the virus. It could also be assumed that the percentage of C3d detected 'Berzuini et al, Blood, 2020' is due to alterations of the complement receptors present on the surface of the red blood cells caused by the activation of the complement against the protein N of the nucleocapsid of the virus Sars Cov2 'J.E.Hendrickson and C.A.Tormey, Blood, 2020'.
ABSTRACT
Background: The Severe Acute Respiratory Coronavirus 2 (SARS-CoV- 2) infection manifests itself through a wide range of clinical pictures, from the condition of asymptomatic carrier to severe respiratory insufficiencies and/or severe organ impairments, including a massive release of cytokines, an increase in the coagulation state, haemoglobin damage, dysregulation of iron homeostasis and iron overload. It has also been appreciated a normo/macrocytic anaemia in many patients, typically associated with phlogosis. In effect, the condition of inflammation deeply affects erythropoiesis through different mechanisms, both linked to an altered iron metabolism mediated by an increased production of interleukins, and caused by proinflammatory cytokines such as the interferon-γ, IL-1, IL-33 and the Tumour necrosis factor-α (TNF-α). Inflammatory cytokines, especially IL-6 and IL-1b, increase the production of hepcidin, which, by degrading ferroportin, the cellular exporter of iron, provokes a reduction in serum iron and a sequestration of iron at the macrophage level. This process deprives potential microorganisms of iron, but it can cause a typically macrocytic anaemia, also known as 'anaemia of chronic disorders'. An altered iron metabolism would therefore be expected also in the SARS-CoV-2 infection. Nevertheless, studies on alterations of the iron metabolism in this infection are still quite limited. Aims: Our study is a retrospective analysis aimed at understanding the Covid-related pathogenesis of anaemia through the data examination of patients transfused during the SARS-COV2 infection. Methods: In our Immunohematology and Transfusion Medicine Service, we have analysed the types of anaemia occurred in patients suffering from SARS-CoV-2 who have been subjected to blood transfusion in a period comprised between November 2020 and December 2021. We have evaluated data in relation to 29 patients presenting normo-macrocytic anaemia at the onset, subjected to a transfusion of prefiltered red blood cells. The analysed sample included 15 males and 14 females with an average age of 67 years (range: 40-96). Only 4 patients out of 29 had a haemorrhage at the onset. The other 25 patients did not incur into haemorrhagic episodes. Results: Average pre-transfusion blood counts have highlighted an average haemoglobin value of 7.5 g/dl (range: 6.4-9.2) with an average globular volume of 93 fL (range: 65.3-105). Patients have been transfused on average with 4 units of prefiltered red blood cells (range: 1-24). All patients presented a severe phlogosis documented by average ferritin values of 520 ng/ml (range: 355-1200) and of CRP of 8.7 mg/dl (range: 1.79-25). Summary/Conclusions: Analysed data lead us to think that, as it has been confirmed by the scarce literature on the matter, the majority of cases of anaemia associated with a SARS-CoV-2 infection has an inflammatory pathogenesis. The high values of the serum ferritin and of the CRP strengthen this hypothesis. There is surely an additional etiopathogenetic component of bone marrow inhibition on the erythrocyte maturation associated with an alteration of iron metabolism, as it can be deduced from the increase in the average globular value.