Uses and Unknowns in Convalescent Plasma Therapy
Mon, April 19, 2021

Uses and Unknowns in Convalescent Plasma Therapy


Convalescent plasma therapy is a popular treatment in COVID-19. However, the therapy has been around for quite some time and can be used in different cases, beyond COVID-19 treatment. Still, research cannot exactly determine how much plasma therapy can help patients.

The different uses and mysteries of convalescent plasma therapy were revealed by the Mayo Clinic, an American not-for-profit medical center. Aside from providing antibodies for COVID-19 patients, the therapy could be utilized as a replacement fluid and a replacement for depleted blood clotting factors. The therapy would be automatically involved in any patient who suffered massive blood loss due to trauma or other causes.

The Uses of Convalescent Plasma Therapy

Today, convalescent plasma therapy may mean one thing for most people: a COVID-19 treatment. While there is no denying that it is applied in COVID-19 patients with severe symptoms, the therapy has been purposely applied to save the lives of those afflicted by other health threats. In the COVID-19 setting, the therapy uses the antibodies obtained from a survivor and then transfuses them into a critically-ill patient. The transfusion material is sometimes called liquid gold because of the color of the blood plasma.

According to the American Society of Hematology, a professional organization of hematologists, the therapy became an optional treatment for COVID-19 due to its long history of therapeutic benefits. Its use dates back nearly 100 years ago, even before the discovery of antibodies. Before antibodies were known, physicians identified that some people survived fatal illness while others perished. This led to the procedure of transferring the survivor's blood into infected individuals, but the proper process of extracting antibodies called plasmapheresis refined the procedure, wherein donors could provide plasma to others without risking their health.



Some of the diseases found with evidence of benefits from plasma therapy include rabies, polio, influenza, measles, Ebola virus disease, and hepatitis B. Even results in studies of Severe Acute Respiratory Syndrome (SARS) and the Middle East Respiratory Syndrome (MERS) suggested benefits from the therapy. Though, the evidence was not as concrete compared to studies of other medications. The accuracy to determine the exact mechanisms behind plasma therapy remained problematic.

With COVID-19, theoretical benefits from plasma therapy were revealed by biomedical scientists and medical doctors. Those who recovered from the novel disease exhibited new antibodies, showing that their plasma could be utilized as an assistive treatment. This means their plasma could be transfused to another patient to provide short to medium term humoral immunity, which involves antibodies that combat pathogens. The idea is to transfuse plasma to neutralize the SARS-CoV-2 virus. This may reduce symptoms and boost the recovery rate of the recipient.

Because scientists have confirmed the existence of antibodies against the novel coronavirus, hospitals in different countries are now urging survivors to donate plasma to save more lives. As long as they fulfill the requirements, they are allowed to donate liquid gold to help critically-ill patients.

Beyond COVID-19, the most basic purpose of plasma therapy is to stabilize a patient who has lost a lot of blood. Plasma is included in blood products normally transfused in patients who are in surgery or are being treated for major injuries. The therapy stabilizes the patient using the contents in the plasma, like enzymes, proteins, and salts. As such, plasma therapy is essential in treating patients who suffered trauma and patients with rare, chronic illnesses.

"In medical emergencies with massive blood loss, patients undergo blood transfusion as a life-saving treatment, and plasma is one of the blood products typically transfused," said Dr. Camille van Buskirk, medical director of the Blood Donor Program at the Mayo Clinic.

Another application of plasma therapy is in the treatment of blood disorders. Specifically, convalescent plasma therapy can be used to treat patients with clotting problems. The therapy replaces blood clotting factors depleted by massive blood loss, inhibited by certain medications, and subdued by inherited disorders. Even after overcoming COVID-19, plasma therapy will remain a crucial part of saving human lives.



The Unknowns in Plasma Therapy

Despite what evidence suggests, there are still many unknowns in convalescent therapy. One of these is no one can precisely tell how much plasma therapy helps patients. This means there is no measure to accurately quantify percentages of recovery, improvement, and protection. The reason behind the lack of measurements is the absence of randomized, controlled trials to guarantee results. Since COVID-19 itself has many unknowns, results in controlled trials of plasma therapy may not be exact.

Another is that the side effects of plasma therapy across all diseases are mostly undiscovered. For COVID-19, the adverse effects are insignificant, at least, in the majority of cases. Dr. Michael Joyner, a professor at the Mayo Clinic, said that a recent publication suggested plasma therapy as safe for COVID-19 patients. The same publication highlighted evidence that the viral load of SARS-CoV-2 in the blood is either reduced or eliminated, in those who received plasma therapy. But the therapy remains a nonstandard treatment because of its variability. The efficacy of plasma therapy in COVID-19 is subject to the number of antibodies from the donor and the current state of the patient.

The mystery of side effects is affected by the lack of data from clinical trials. Plasma therapy can pose a risk to the recipient if there is another infectious pathogen, if the recipient has an adverse reaction to the plasma, and if one has severe lung problems. But side effects centered around the interactions between the donor's antibodies and the different parts of the immune system, which may react to the transfused proteins, are poorly understood.

Meanwhile, a study published on March 27, 2020 in the journal JAMA Network, showed the findings of treating five critically-ill COVID-19 patients with plasma therapy. The patients were confirmed infected with SARS-CoV-2 and developed acute respiratory distress syndrome. They were also confirmed with rapidly progressing severe pneumonia and increasing viral levels, in spite of receiving antivirals. Attending physicians administered convalescent plasma therapy to all patients between 10 and 22 days after their admission. Then, measures including the changes in body temperature, the potential of organ failure, and the levels of the virus were taken during the study period.

Overall, the therapy normalized the body temperature of four patients within three days after administration. Their organ failure score decreased and their breathing rate improved within 12 days after administration. For the organ failure score, the scores were five for patient one, 10 for patient two, three for patients three and four each, and two for patient five before transfusion. On day five after transfusion, their respective scores were five, 11, two, two, and two. And on day 12 after transfusion, their respective scores significantly decreased to two, four, two, one, and one. Only patient two had a slower improvement rate in terms of organ function.

For survivors who want to donate their plasma for COVID-19 patients, they have to be free of symptoms between 14 and 28 days. They also have a negative PCR test result for COVID-19. Lastly, they must meet the standard requirements for blood donation.