Blood clotting and COVID-19: a growing concern

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Early on researchers had observed the complications of abnormal blood clotting in COVID-19 patients. 

D Dimer, a coagulation marker, is playing an important role in early identification of complications caused due to blood clotting and thus aiding in treatment of severe COVID-19 cases.

How blood clots are proving to be fatal in COVID-19

Early on, while doctors were still trying to understand COVID-19, signs of blood clotting were being detected in different organs. Nephorologists were noticing dialysis catheters getting plugged with clots. Neurosurgeons were witnessing a surge in patients with strokes. 

“Researchers have found stroke rate to be seven times higher in patients with severe COVID-19 than those with severe seasonal flu(1).”

Evolving clinical resources confirm a convoluted role of abnormal blood clotting in COVID-19 that manifests in the form of both micro thrombosis (formation of small blood clots) and venous thromboembolism (VTE). VTE is a condition when a blood clot may break off or embolize and lodge in distant vessels. For e.g., a blood clot or thrombus that originates as a deep venous thrombosis (DVT) in the large veins of the legs may embolize to the lungs, resulting in pulmonary embolism (PE).

So what exactly happens in COVID-19?

At the beginning of the pandemic, doctors initially thought that the virus was only causing respiratory infection. However, it is now evident that COVID-19 also causes inflammation of the blood vessels of the lungs, leading to their narrowing. This in turn causes a state of hypercoagulopathy and promotes clotting. 

In patients with severe COVID-19, a cytokine storm occurs that can cause death. This is an uncontrollable secretion of pro-inflammatory cytokines (small proteins secreted by the immune system to control the spread of infection) in a short span of time. A cytokine storm can thus trigger inflammation, leading to an overactive coagulative system. This in-turn increases the risk of disseminated intravascular coagulation (DIC), where clots in the bloodstream are disseminated throughout the body.  

Doctors have since then reported abnormal blood clotting and cytokine storm as the two most common reasons behind the death of COVID-19 patients.  

PE and COVID-19

“Recent studies indicate that there is a high risk of mortality in patients with COVID-19 and PE as 15-39% of them require mechanical ventilator support(2).”

Immobility and restricted activity during the course of treatment leads to an increase in the prevalence of PE. Not just that, there is a disturbing trend that indicates that many people who have recovered from COVID-19 may need to be treated for blood clots. Pulmonologists across the world have been flagging these conditions, as patients who have recovered from COVID-19 are going back to hospitals with breathing problems due to lung damage caused by PE.

Testing for D Dimer: critical to the treatment of COVID-19

D Dimer is a small protein fragment that is left floating in the blood when a clot is degraded by the process of fibrinolysis. Normally it would go away with time. However, its presence in high levels in the blood is indicative of major clots. It aids in diagnosis of VTE by being an early, sensitive marker for DVT, PE, DIC and coronary artery disease. 

A negative result rules out thrombosis, therefore, D Dimer is used by medical experts to definitely rule out thromboembolic diseases, especially where the probability is low. 

Studies have concluded that many COVID-19 patients admitted to hospitals had increased D Dimer levels, indicating an increased risk of abnormal blood clotting. A four-fold increase is a strong indicator of mortality in those suffering from COVID-19.

Recent IFCC guidelines recommend D Dimer testing in patients with COVID-19. A D Dimer value >1000 ng/mL is alarming for a COVID-19 patient with VTE complications.

Methods for detecting D Dimer levels

Enzyme-linked immunosorbent assay (ELISA), chemiluminescence immunoassay (CLIA), immunofluorescence assay (IFA), point-of-care testing and immunoturbidimetric assay are various methods for D Dimer detection. The automated latex-enhanced immunoturbidimetry assay on coagulometer is the most commonly used technology and provides valuable information about the prognosis of thromboembolic disease. 

This quantitative method is preferred for being faster, with higher sensitivity and specificity and easy to process on fully automated coagulation analyzers.

Variances in reporting

Depending on the method, results are reported as fibrinogen equivalent unit (FEU) or D Dimer unit (DDU). FEU is 1.7 times higher than DDU. This can lead to significant errors during method comparison. It is thus necessary for laboratories to comply with the reporting recommendations of the reagent manufacturer.

Erba D Dimer R

COVID warriors continue to rely on companies such as Transasia to aid this fight with proven solutions for early and accurate diagnosis. Transasia-Erba Group provides high quality Immuno-turbidimetry assay for D Dimer detection. The kit aids in monitoring the change in D Dimer concentration in the sample for exclusion of DVT and PE. The assay is pre-programmed and can easily be performed on ECL series systems. 

Authored by:






Dr. Omkar Kadhane

Dy. Product Manager - Coagulation

Transasia Bio-Medicals Ltd. 

References: 

  1. https://local12.com/health/health-updates/many-people-with-covid-19-may-need-to-be-treated-for-blood-clots-cincinnati
  2. Agnes Lee, et al; COVID-19 and Pulmonary Embolism; American Society of Hematology June 2020

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