Clots, COVID-19 and survival

The novel coronavirus, now known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that causes COVID-19 disease, was first reported in Wuhan, Hubei Province of China in late December 2019. Since then, it has infected a large population across the world with the current number of SARS-CoV-2 infections standing at over 13 million and COVID-19 disease having killed over 571,000 individuals.

Now, researchers from the Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, have performed a retrospective study looking at all the hematological characteristics of the disease as well as the risk factors that can predict the outcome of the disease.

Their study titled “Hematological characteristics and risk factors in the classification and prognosis evaluation of COVID-19: a retrospective cohort study” is published in The Lancet Haematology on 10th July 2020. The study was funded by the National Key Research and Development Program of China.

Present status of the pandemic

The pandemic of COVID-19 is far from over, and one of the most important clinical features of the disease are the changes in the vascular system and hematological features. The researchers wrote that there is an onset of flu-like symptoms followed by severe complications, multi-organ failure, and death in some individuals.

The reports from around the world show that nearly 20 percent of those infected can become severely ill, and these individuals have a risk of death ranging from 8.1 to 33 percent.

Severe disease

The team wrote that the National Health Commission of China had classified the severity into four levels based on the clinical features.

These include “mild, moderate, severe, and critical disease.” The criteria for these levels include “respiratory rate, oxygen saturation, and lesion progression in pulmonary imaging,” they wrote. In some other hematological features may be predominant. These include “septic shock, heart failure, and disseminated intravascular coagulation (DIC).”

Some may have coagulation problems such as “ischaemic limbs, strokes, and venous thromboembolism.” The latter, the team wrote, is one of the most prevalent presentations in severe COVID-19 disease.

Why was this study undertaken?

This was a retrospective cohort study. This meant that the researchers looked at COVID-19 cases over the last few months and, based on common parameters, tried to determine the hematological characteristics and the risk factors.

They had noted from previous studies that among those who did not survive, the risk of coagulopathy or coagulation disorders was high along with abnormal results on coagulation tests. These individuals also had other thrombotic complications, such as bleeding and multi-organ failure.

The team speculated the coagulation markers such as “neutrophil to lymphocyte ratio, platelet count, D-dimer, and prothrombin time,” if performed early, could help predict the outcome of the COVID-19 patients.

How did they go about conducting the study?

The team worked on COVID-19 patients who were admitted to three different sites under Wuhan Union Hospital (Wuhan, China).

For each of the patients, they included demographic details, clinical findings, laboratory reports, treatment details, and final outcome details. These were obtained from the electronic medical records.

A comparison was made between moderate, severe, and critical disease based on the “diagnosis and treatment protocol for novel coronavirus pneumonia, trial version 7, published by the National Health Commission of China”.

Using several scoring systems, the team identified the risk factors for poor outcome of COVID-19 among the patients.

What did they find?

A total of 466 patients were included in the study and these participants were admitted to the hospitals between 23rd January and 23rd February 2020.

Of these, 380 were included in the final analysis in the study. Results were as follows;

  • Of all the patients low platelet count of thrombocytopenia (defined as a platelet count less than 100  × 109 cells per L) seen among –
    • 42 out of 86 (49 percent) patients with critical disease
    • 20 out of 145 (14 percent) patients with severe disease
    • 9 out of 149 (6 percent) patients with moderate disease
  • Those with critical disease had lower counts of lymphocytes and eosinophils compared to those with severe or moderate disease
  • Coagulation markers such as prothrombin time, D-dimer, and fibrin degradation products were significantly raised in critical patients
  • Risk of death was higher among those with increased neutrophil to lymphocyte ratio of more than or equal to 9.13.
  • Risk of death rose with thrombocytopenia (platelet count <100 × 109 per L)
  • Risk of death rose with prolonged prothrombin time (>16 s)
  • Risk of death rose with increased D-dimer (>2 mg/L)
  • Among all patients who died, there was the incidence of bleeding and coagulation related complications (19 out of the 55 who died, i.e., 35 percent)
  • Among those who died, sepsis-induced coagulopathy and International Society of Thrombosis and Hemostasis overt disseminated intravascular coagulation scores were also raised. The team wrote that those who developed DIC typically first had sepsis-induced coagulopathy.

Implications and conclusions

The team wrote in recommendations, “Rapid blood tests, including platelet count, prothrombin time, D-dimer, and neutrophil to lymphocyte ratio, can help clinicians to assess severity and prognosis of patients with COVID-19.”

They also urged clinicians to use the sepsis-induced coagulopathy scoring system for assessment of critically ill patients early in their course of management.

The team wrote, “In conclusion, coagulopathy is a non-negligible complication and potentially important cause of death in patients with critical COVID-19.”

Journal reference:
Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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