A blood test taken 48 hours after cardiac arrest could help predict a survivor’s long-term memory and thinking, researchers say.
The study found that measuring neurofilament light chain, or NfL, was significantly better at predicting later memory and thinking problems than the blood marker now used by doctors. NfL is a protein released into the blood when brain cells are damaged.
The current standard test measures neuron-specific enolase, or NSE, but there are concerns about its reliability because factors other than brain damage can raise levels.
The research, carried out by a team from Rigshospitalet, Copenhagen University in Denmark, was presented at ESC Acute CardioVascular Care 2026, the annual congress of the Association for Acute CardioVascular Care, part of the European Society of Cardiology.
The study analysed blood samples from participants in the Blood Pressure and Oxygenation Targets after Cardiac Arrest trial, known as BOX, who had been resuscitated after an out-of-hospital cardiac arrest and were comatose on hospital admission. Levels of NfL and NSE were measured in samples taken 48 hours after cardiac arrest.
Data on cognitive function, assessed months later using the Montreal Cognitive Assessment, or MoCA, were available for a subset of survivors who had both NfL and NSE measurements. MoCA is a widely used test for memory and thinking problems.
The key finding was that NfL levels at 48 hours were inversely correlated with MoCA score, meaning higher blood levels were linked to worse long-term cognitive function. No such association was observed for NSE.
Dr Martin Meyer from Rigshospitalet, Copenhagen University said: “Currently, we measure neuron-specific enolase in the blood as a marker of brain injury but there are concerns about its reliability as factors other than brain damage can lead to high levels.
“Another blood biomarker, neurofilament light chain, has potentially better diagnostic performance than neuron-specific enolase. We compared neurofilament light chain and neuron-specific enolase for the prediction of long-term cognitive function in survivors of out-of-hospital cardiac arrest.”
Summarising the findings, Meyer said: “Neurofilament light chain levels measured early after cardiac arrest, while patients were still admitted to hospital, were related to long-term cognitive function. This association with cognitive function was not observed with neuron-specific enolase testing.
“The introduction of routine early neurofilament light chain measurement could potentially assist in the identification of patients at high risk, helping to optimise decision-making about other tests and scans, improve the targeting of rehabilitation and enable clinicians to better inform patients and their families about expectations for the future.”
Further validation and standardisation of neurofilament light chain assays are now needed.
