Anaemia and blood transfusion in COVID patients

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.