D-dimer Values as a Biomarker of COVID-19 Severity

The second wave of the COVID-19 pandemic is ravaging several countries of the world, including India. Compared to 2020, the number of deaths due to the virus could be lower, thanks to vaccination efforts all over the country. However, it is not clear by when the entire population will be vaccinated. Till then, mortality is one of the risks of the disease.

For scientists and the medical fraternity, it’s imperative to come up with new mechanisms to identify patients who are at significant risk of mortality so that the right interventions can be initiated and the patient saved. D-dimer levels in the patient’s blood can be a useful biomarker in this regard.

What Is D-dimer

The bio-medical explanation of what D-dimer is can be fairly complex and technical. However, we will try to simplify it for you.

Whenever the body sustains an injury or trauma, coagulation or clotting of blood happens to minimize bleeding. The liver produces several proteins to achieve this, one of them being fibrin, which constitutes the clot material. The size of the clot must be limited; else, it can grow rapidly creating new risks. Further, the clot material or fibrin must be degraded or broken down eventually once the risk of bleeding is eliminated.

Fibrinolysis is the process of breaking down the fibrin. During fibrinolysis, a certain protein fragment is formed, and this fibrin degradation product or FDP is called D-dimer. The name is so because the molecule can be compared to a dime or coin in structure.

D-dimer molecules have an approximate lifespan of 16 hours after which they are broken down by the body and flushed out by the kidneys. High levels of D-dimer in the blood can be an indicator of thrombotic activity or unwanted coagulation happening in the body. For this reason, it’s been used as an indicator or biomarker for thrombosis (unwanted blood clots that can be life-threatening) since the 1990s. Risk factors for thrombosis are chronic inflammatory disease, active cancer, immobilization due to an accident, recent surgery, pregnancy, and advancing age.

D-dimer as a Biomarker for COVID-19

A majority of Covid-19 patients fall into the low-intensity category, a small group into the moderate intensity, and around 5-10% in the severe intensity category where mortality is a risk. The patients in the severe category suffer from conditions like hypoxia (low oxygen), pneumonia, and respiratory failure. Some of them suffer from acute respiratory distress syndrome (ARDS) and multiple organ failure (MOF). ARDS and MOF are very high-risk factors for mortality in COVID-19 patients.

However, why some patients decline towards ARDS and MOF and why some don’t is quite unclear. In the absence of this understanding, any indicator that can differentiate patients with a high risk of mortality from low-risk ones is useful, so that the right intervention can be done and the person’s life saved. This is where D-dimer comes into the picture.

Ever since the pandemic broke out in early 2020, researchers worldwide have been looking for clues to reduce mortality risk. Chinese scientists in Wuhan and other hospitals across China have also been conducting such research.

Between 31^st January and 12^th February 2020, a Chinese hospital conducted tests on 274 Covid-19 patients with a median age of 62 years. Out of these 274, eventually, 161 patients survived, while the remaining 113 did not. Thorough blood analysis of these 274 patients revealed that the 161 survivors had an average D-dimer level of 0.6 micrograms/milliliter while the deceased had an average D-dimer level of 4.6 micrograms/milliliter.

Outlook

This only confirms the opinion that abnormal coagulation function and hence elevated D-dimer levels in the blood have a connection to mortality risk or severity levels of COVID-19 infection. However, correlation doesn’t always indicate causation, so more research and clinical studies are required before establishing a clear connection. Till then, D-dimer levels can be used as a biomarker in addition to several other medical parameters in patients while assessing their mortality risk.

 

Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.

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