In a recent interview for The Spin, Dr Margot Putukian identified blood biomarkers (substances measured in blood that may provide information about brain injury) as an area that could eventually change concussion assessment. She also acknowledged how much of our current diagnosis depends on clinical assessment and athletes reporting their symptoms honestly.

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While an objective biological measure is an appealing prospect, and there are many markers that we can measure, these tests do not yet provide a straightforward answer. .

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Axis is currently partnering with the Auckland University of Technology (AUT) to help investigate the role of concussion biomarkers in sport. These tests may eventually help clinicians assess concussion and recovery, but there is still significant uncertainty about what these test results might mean.

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For example, consider a player who leaves the field after a head impact. Their history observed signs and clinical assessment support a diagnosis of concussion, but the biomarkers are low. Does that mean the player is not concussed?

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Now consider the reverse. A player feels well, has returned to their usual clinical function and has progressed through rehabilitation. Their blood biomarkers remain elevated. Does that mean they cannot play?

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These hypothetical scenarios capture an important challenge. So before introducing a test into clinical practice, we need to understand which decisions it can reliably inform. There is no single 'concussion biomarker'

Blood biomarkers are measurable substances that may provide information about an injury or biological process. There are many candidates relating to brain injury, and 'biomarker testing' describes a broad field rather than a single test.

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Some markers, including GFAP and UCH-L1, have been investigated in sporting populations. Others have evidence drawn largely from hospital patients with head injuries or remain at an earlier stage of investigation. Even among markers studied in sport, the amount and quality of evidence vary considerably.

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For example, each marker related to a different biological process, may rise at different times and may remain elevated for different periods. As a result, evidence supporting one marker, measured on a particular device at a particular time, cannot automatically be applied to another marker or testing method.

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There is also a distinction between a biological change and knowing what it means for a player.

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Some tests already have a defined role in assessing head injury. For example, GFAP and UCH-L1 markers are used to help clinicians determine whether selected adults with suspected mild traumatic brain injury need a head CT. Its intended use concerns the likelihood of an injury visible on CT, a different question from whether a player has concussion, or whether they can return to contact sport.

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Margot highlighted this distinction during our discussion. Evidence that a test helps with emergency department imaging decisions cannot simply be transferred to the sideline. More data and evaluation is needed.
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When the blood test and clinical assessment disagree

Consider the existing head injury assessment process that is used in most contact sport. Clinicians bring together a mechanism, observed signs, symptoms, examination and repeat assessment. Where would a blood test fit into this process?

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At present, a low result cannot reliably overturn a clinical diagnosis of concussion.

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A 2026 CARE Consortium study included 323 athletes with concussion. Using the study's definition of meaningful change from baseline, 37% has no elevation in any measured marker during the first 24-hours post injury.

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This finding was supported by data from professional rugby study where a 36-hour follow-up assessment, the combination of GFAP and S100B identified only around half of the concussion episodes studied. This data means that positive results could support the diagnosis, but negative results missed many diagnosed injuries.

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In contrast can someone who's markers remain elevated return to sporting activity? A 2024 study in Australian rules football followed 81 players with concussion and 56 controls. In this study some of the injured players had substantial, prolonged biomarkers elevations, remaining elevated for us to 12 weeks.

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The findings suggest that biological changes can extend beyond apparent clinical recovery. The clinical significance of this elevation is uncertain as no study has established a blood concentration above which playing is unsafe or demonstrate that waiting for normalisation prevents another injury.

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At present this persistent elevation creates an important research question, rather than an established return-to-play criteria. We need more data linking these measurements to outcomes that matter including further injury, recovery and longer-term brain health.
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Bringing the research into sport

Our partnership with AUT is intended to help us understand how these measurements might contribute to athlete care.

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AUT's broader programme is examining questions including sampling times, recovery and factors that may influence biomarker concentrations. Our sporting collaboration provides an opportunity to investigate how these measurements relate to the clinical assessments already used in athlete care.

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I am especially interested in how to use these results reliably to support the existing tools we have to make clinical decisions, particularly in rugby league and in New Zealand sporting settings.

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I also note that sporting organisations are keen to incorporate objective measurements, for example the NRL has previously said it would like to incorporate blook and salvia testing into the HIA process.

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Based on current data biomarkers are still a research tool. Interest in a new technology does not establish its readiness for routine use.