A prominent haematologist has sounded the alarm over the use of unproven long COVID treatments in the UK, after reports that a teenager received anticoagulants off-label to treat the condition.

The experimental use of anticoagulants and plasmapheresis to treat long COVID is hotly contested, with some families spending thousands of pounds to travel to Europe to get the treatment privately.

But the Guardian reported this month that a 15-year-old girl under private care in the UK “made improvements” after receiving blood thinning medication to inhibit so-called “microclots” on the advice of a paediatric cardiologist.

The UK specialists involved in her care – Manchester-based Respiratory Consultant Dr Binita Kane and an unnamed cardiologist – “believe [microclots] stop oxygen getting around the body as it should and could be one reason behind some of the symptoms of long COVID”, the article from 12 June said.

Evidence for ‘microclot’ theory is ‘tenuous’ – haematologist

Responding in a letter to the editor, Professor Beverley Hunt, a Professor of Haematology at Guy’s Hospital in London, said “the evidence base for ‘microclots’ causing long COVID is tenuous to say the least”.

There is “no evidence” to suggest that anticoagulant therapy is effective for people with the condition, the letter, also signed by Cochrane researchers Dr Rebecca Kuehn and Professor Paul Garner, continued.

“These drugs can have serious side-effects, which raises ethical concerns if they are used outside well-conducted scientific randomised trials,” they said.

Professor Hunt, along with Dr Kuehn and Professor Garner from the Liverpool School of Tropical Medicine, have published a number of articles challenging the “microclot” hypothesis of long COVID pathophysiology, which is the basis for the theoretical effectiveness of anticoagulants and plasmapheresis in the treatment of the condition.

Their work has demonstrated that “microclots” are actually amyloid fibrin(ogen) particles, which are not involved in blood clotting and are not exclusive to patients with long COVID.

“We conclude the inferences for the hypothesis are not based on evidence, unlicensed use of antithrombotic medication is not justified, and apheresis should not be considered outside of a well-designed clinical trial,” they concluded in an article in the May issue of Research and Practice in Thrombosis and Haemostasis.

Evidence is ‘indisputable’ – Respiratory Consultant

However, Dr Kane, who is a consultant respiratory physician at Manchester University Foundation Trust and also works at private provider the Howell Medical Group, has since claimed on X (formerly Twitter) that “the evidence is indisputable”.

In a tweet on 22 June, Dr Kane shared what she described as “important work from the Harvard Paediatric group demonstrating increased levels of microclots, activated platelets and clotting-related proteins in children with #longcovid compared with healthy controls”.

The abstract from the 2024 American Thoracic Society International Conference described the use of microscopy and proteomic analysis to test whether microclots were present in the blood of children with multisystem inflammatory syndrome, acute paediatric COVID or long COVID.

The full paper is yet to be published, Dr Kane noted, adding in a separate tweet that it takes time to publish high quality research. “For those not involved in (or interested in) the research/treating patients, they will inevitably be two years behind the science,” she said.

The limbic asked the British Cardiovascular Society and the British Heart Foundation whether they had a position on the use of anticoagulants and plasmapheresis for the treatment of long COVID, but neither organisation provided a response.

Professor Hunt told the limbic there was “little evidence” that UK health professionals were using anticoagulants and plasmapheresis to treat long COVID but that it continues to be offered overseas.

She has previously expressed her concerns about patients travelling abroad to pay for and receive the treatments privately. An investigation by the BMJ and ITN in 2022 found that patients with long COVID were travelling to private clinics in Cyprus, Germany, and Switzerland for plasmapheresis and anticoagulation.