- The incellKINE test is based on research identifying immune cells that are raised in long COVID patients.
- The developers claim the test provides greater than 90% accuracy in detecting long COVID.
- The EU has approved the test for sale and distribution, available from the end of September.
- The UK has its own approval authority and has not yet approved the test.
The first diagnostic blood test for long COVID screening has been approved by European regulators, raising hopes for the millions of sufferers of this debilitating condition which can arise after a COVID-19 infection.
Long COVID refers to lingering post-viral symptoms after SARS-CoV-2 infection that persist for months after the initial infection. The condition is also known as Post-Acute Sequelae of COVID-19 (PASC).
The symptoms commonly include fatigue, pain, malaise, sleep disturbance, cognitive decline, POTS (symptoms caused by a fall in blood pressure when standing), post-exertional malaise, dyspnoea (shortness of breath) and other symptoms.
As of 4 June 2022, an estimated two million people in the UK (3% of the population) were experiencing self-reported long COVID (symptoms continuing for more than four weeks after the first suspected infection that were not explained by something else) (see Figure 1 in this survey). This is a truly staggering figure.
Researchers in the UK, Europe and around the world have been in a race to understand the causes of long COVID and to develop diagnostic tests to aid doctors.
The California-based IncellDx has received regulatory certification for its ‘incellKINE Long COVID In Vitro Diagnostic test’ in Europe, which helps in the objective diagnosis of patients with PASC.
The developers claim that the test is one of the first to market to detect long COVID, by identifying unique immune signatures. (In August, ME Research UK posted news of talks at the IACFS/ME annual conference where the immune signature profile of long COVID and ME/CFS was presented.)
The test was developed based on clinical studies published in the peer-reviewed journal Frontiers in Immunology which showed immune biomarkers (cytokines and chemokines) linked to long COVID status. These biomarkers can trigger inflammatory responses in response to infectious agents such as viruses.
In the first study, levels of a number of monocytes (white blood cells involved in killing invading organisms) were increased in PASC patients for up to 15 months after the initial, acute COVID-19 infection. Many of these cells were confirmed to contain SARS-CoV-2 protein, both in patients with severe COVID-19 and those with PASC.
In further experiments, the researchers investigated these monocytes as well as B cells and T cells (responsible for controlling the immune response) in groups of patients with mild/moderate and severe COVID-19, and in those with PASC.
These specific patient groups could be characterised by different patterns of these cells. In particular, the findings in the patients with PASC (or long COVID) suggest that these individuals may not have had a well-enough targeted immune response to overcome their initial viral infection. This may then have led them to develop a complex inflammatory response that could be the root cause of the symptoms they experience.
Such a model has long been suspected in ME/CFS as well, including Dr Melvin Ramsay’s post-infectious disease model of the 1950s, or the very recent Metabloic Trap Model from Professor Ron Davis, with viruses like Epstein-Barr virus implicated.
The incellDx test may pave the way for similar testing on ME/CFS patients, and we know that researchers at Yale University and elsewhere are comparing the immune profiles of ME/CFS patients with their long COVID patients.
This marks an exciting evolution in the scientific understanding of post-viral fatigue syndromes that could revolutionise diagnosis and treatment.