COVID-19 Research By University Of Rochester Shows That Lymphocytopenia Prior To Getting Infected With SARS-Cov-2 Increases Mortality Risk
: A new study by scientist from the Department of Pathology and Laboratory Medicine at the University of Rochester Medical Center have found that lymphocytopenia (A condition of having a low white blood cell count) prior to exposure to SARS-CoV-2 coronavirus may be associated with an increased risk of dying from COVID-19 disease.
Lymphocytopenia is caused by a variety of factors but it may also may be inherited or caused by various infections or medical conditions, drugs, or autoimmune disorders. (please refer to end of article for details)
The research findings were published on a preprint server but are currently being peer reviewed. https://www.medrxiv.org/content/10.1101/2020.10.02.20200931v1
The research of SARS-CoV-2-infected individuals who also had at least one complete blood count available from the ten years preceding any potential exposure to the virus found that pre-2020 lymphocytopenia was associated with an increased risk of COVID-19-related death.
The study team says that patients who had pre-existing lymphocytopenia were at a 1.4-fold greater risk of dying from COVID-19 than individuals who did not have lymphocytopenia prior to 2020
Co-researcher Dr Xueya Cai from the Biostatistics and Computational Biology Deparment of University of Rochester Medical Center told Thailand Medical News, “These data show that pre-2020 lymphocytopenia is associated with an increased odds ratio of death. Because the absolute lymphocyte count is almost universally available and easily interpreted, this biomarker of the risk of fatality could be widely useful.”
It has been observed that the clinical course of COVID-19 varies significantly between individuals. For instance, while around one-fifth of people in their seventies who become infected with SARS-CoV-2 develop symptoms of COVID-19, a similar proportion in this age group never develop any symptoms.
Interestingly such variable health outcomes have inspired great research efforts to identify potential prognostic biomarkers that may pre-exist the development of COVID-19, such as the presence of co-morbidities or predisposing genetic factors.
Significantly it was found that Lymphocytopenia is a common feature among COVID-19 patients and, importantly, a continuing decrease in the absolute lymphocyte count (ALC) is considered a risk factor for respiratory failure and death.
Dr Cai added, “Given this association between fatality and lymphocytopenia during COVID-19, we hypothesized that lymphocytopenia prior to any possible infection by the virus could be a risk factor for fatality.”
In order to tests this hypothesis, the study team identified 1,337 patients (aged a median of 61 years) with SARS-CoV-2 infection confirmed by polymerase chain reaction (PCR) who also had at least one complete blood count available from the decade before 2020, thereby ensuring these blood counts pre-dated any possible exposure to the virus.
Importantly bivariate analysis pointed to an association between pre-existing lymphocytopenia (defined as
an ALC of 0.9x109 /L) and COVID-19- related death.
In addition, logistic regression analysis adjusting for patient age and the number of ALCs obtained indicated that patients who had pre-existing lymphocytopenia were 1.4 times more likely to die from COVID-19 than those who did not.
The study team says the mechanisms underlying the association between a low pre-COVID ALC and an increased fatality risk are unclear.
Dr Cai further added, “There is widespread interest in whether baseline immune-status affects fatality and simply the lymphocyte number may be a reflection of the immune status.”
A reduced ALC alternatively, may reflect the use of therapies for various different disorders that could only be identified by reviewing each medical record individually, they add.
Dr Cai and colleagues say that absolute lymphocyte count or ALC could be widely useful as a biomarker of the risk of COVID-19-related fatality.
The team concluded, “Because the ALC is a simple and almost universally available test, the association of pre-COVID lymphocytopenia with fatality may allow individuals and providers to succinctly communicate personal risk, facilities to streamline the triage of resources for isolation, and epidemiologists to improve pandemic-scale modeling.”
Typically Lymphocytopenia may be a sign of an underlying illness, condition, or other factor. The majority of causes are acquired. This means that you develop rather than inherit them.
T cells make up the greatest proportion of lymphocytes, and T-cell lymphocytopenia is the most common. However, this condition can affect all three cell types.
Conditions that can give rise to Lymphocytopenia:
1. Autoimmune disorders
Autoimmune disorders occur if the immune system is in overdrive and incorrectly attacks the body’s own cells and tissues. These can include:
Certain immunosuppressant medications that are used to treat autoimmune disorders may additionally cause lymphocytopenia.
2. Cancer and treatments for cancer
Various types of cancers especially blood or lymphatic cancers like lymphoma (such as Hodgkin’s lymphoma), Kaposi sarcoma, and leukemia can result in low lymphocyte levels.
The following cancer treatments may also result in lymphocytopenia:
3. Diseases that affect the blood and bone marrow
Such conditions can cause low lymphocyte levels:
Viral, bacterial, parasitic, and fungal infections are a common cause of lymphocytopenia. Any type of serious infection may cause your lymphocyte count to fall. For example:
Note that lymphocytopenia may also be a sign of sepsis or acute bacteremia. The former is a severe infection that causes systemic inflammation, and the latter is a bacterial presence in the blood that could lead to sepsis. Both instances require urgent medical attention.
5. Inherited causes
Inherited or congenital causes of lymphocytopenia are rare. Some of these are:
-severe combined immunodeficiency syndrome
6. Nutritional causes
Malnutrition or undernutrition is typically a common global cause of lymphocytopenia. This occurs because the body lacks protein and other nutrients that are necessary to produce lymphocytes.
An eating disorder, such as anorexia nervosa, may lead to reduced-production lymphocytopenia.
7. Gastrointestinal conditions
Certain conditions that damage the gut wall can affect the body’s absorption of nutrients and may lead to lymphocytopenia in some cases. These are generally referred to as protein-losing enteropathy and include:
-inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
A deficiency of the mineral zinc in your diet can weaken immune health by causing T-cell lymphocytopenia and other immune system dysfunction.
Several drugs can reduce lymphocytes. Medication-induced lymphocytopenia ranges from minor to severe.
The following medications may lower your lymphocyte level:
-azathioprine (Imuran, Azasan)
-carbamazepine (Tegretol, Epitol)
-dimethyl fumarate (Tecfidera)
-methotrexate (Trexall, Rasuvo)
-certain bisphosphonate therapy for osteoporosis
9. Kidney disease
Typically, kidney disease, particularly late stage, chronic disease, can reduce the number of T cells in the blood, but lymphocytopenia can also occur in acute kidney injury.
10. Trauma and surgery
Trauma due to an injury or acute emergency such as cardiac failure can lower lymphocyte counts. Undergoing surgeries such as cardiac bypass can also cause lymphocytopenia.
Other possible causes of lymphocytopenia include alcohol misuse and stress.
Additionally, there is a rare condition known as idiopathic CD4 positive T-lymphocytopenia, in which the cause is unknown.
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