Blood Clot Tests Predict Brain Injury Outcomes, but Fall Short as Treatment Guides

When a patient arrives in the intensive care unit with a devastating brain injury, clinicians face a paradox written in blood. The same injury that causes bleeding inside the skull can also push the coagulation system into overdrive, and the balance between these opposing dangers can shift within hours. Conventional laboratory tests, which measure how long blood takes to clot in a plasma sample, often miss this dynamic chaos entirely. A new umbrella review published in the Journal of Emergency and Disaster Medicine takes the most rigorous look yet at whether a faster, more physiologic family of tests can genuinely improve care for patients with traumatic brain injury, subarachnoid hemorrhage, and ischemic stroke, and its conclusions are more nuanced than many clinicians might hope.

The review, led by Ali Msheik of Hamad Medical Corporation in Doha, Qatar, together with colleagues in trauma surgery, neurocritical care, and medical ethics, synthesized all available systematic reviews of viscoelastic hemostatic assays in neurocritical illness. These assays, which include thromboelastography known as TEG, TEG Platelet Mapping, and rotational thromboelastometry known as ROTEM, differ fundamentally from standard coagulation tests. Instead of isolating plasma and timing a single clotting reaction, they measure the actual physical behavior of clot formation in whole blood: how quickly the clot initiates, how strongly it propagates, how firm the final clot becomes, and how readily fibrinolysis breaks it down. In principle, this gives clinicians a real-time picture of hemostasis that standard tests cannot capture.

To assess the accumulated evidence, the researchers followed PRISMA 2020 reporting guidelines, the Joanna Briggs Institute manual for umbrella reviews, and MOOSE recommendations, searching PubMed, Embase, Scopus, the Cochrane Library, and Web of Science from database inception to January 2026. Two physician reviewers with experience in neurocritical care independently screened records, extracted data, and appraised methodological quality. The screening funnel was dramatic: of 272 records identified, 199 were screened after duplicate removal, and only four systematic reviews survived full-text assessment. The authors emphasized that this narrowing reflects the strict restriction to review-level evidence with reproducible methods and extractable neuro-specific data, not a post hoc reshaping of the question.

Those four reviews encompassed 73 study occurrences representing 63 unique primary studies, spanning traumatic brain injury, subarachnoid hemorrhage, and mixed populations with ischemic stroke and coronary artery disease. A corrected covered area analysis quantified how much the underlying evidence overlapped, finding only slight overall redundancy at 5.3 percent. Within traumatic brain injury, however, the two dedicated reviews shared 12 primary studies, a corrected covered area of 29.4 percent, while the subarachnoid hemorrhage and antiplatelet therapy reviews shared no studies with other clusters. This low overall overlap means the field is not merely recycling the same small trials, an encouraging sign for the maturity of the evidence base even as quality concerns remain.

The methodological appraisal revealed uneven rigor. Using AMSTAR-2, a validated tool for assessing systematic reviews, only one review, a 2021 meta-analysis of thromboelastography in traumatic brain injury by Cannon and colleagues, achieved moderate confidence, supported by a registered protocol, a comprehensive search, duplicate screening, and structured bias assessment. The remaining reviews earned low or critically low confidence ratings owing to absent protocols, incomplete reporting of excluded studies, and limited transparency. When the authors then applied GRADE criteria to rate certainty in individual outcomes, most estimates in traumatic brain injury and subarachnoid hemorrhage fell to low or very low certainty, a consequence of predominantly observational designs, inconsistent definitions, and imprecise effects.

Within those constraints, the prognostic signal was remarkably consistent. Across two reviews covering 32 unique studies in traumatic brain injury, viscoelastic assays repeatedly identified clinically relevant coagulation disturbances. Abnormal clot strength and disturbed fibrinolytic activity were associated with mortality across 18 observational studies, with radiographic hemorrhage progression in 14 studies, and with the need for neurosurgical intervention in nine, though confounding and heterogeneous outcome definitions limited those latter findings. In subarachnoid hemorrhage, a single review of 19 primary studies found that hypercoagulable profiles, particularly increased clot firmness, were consistently linked to delayed cerebral ischemia in six studies and to early brain injury severity in four. These associations make biological sense: dysregulated clot formation and breakdown plausibly contribute to secondary brain injury, hemorrhage expansion, and delayed ischemia after aneurysm rupture.

The therapeutic story was different. No review provided convincing evidence that viscoelastic-guided interventions improved outcomes in traumatic brain injury or subarachnoid hemorrhage, meaning the assays currently function as crystal balls rather than steering wheels in these conditions. The one bright spot came from mixed ischemic populations: moderate-certainty evidence from a meta-analysis of ten studies, including randomized trials, suggested that TEG-guided antiplatelet therapy in patients with ischemic stroke and coronary artery disease was associated with fewer composite ischemic and bleeding events than standard care. Mortality effects, however, remained uncertain because reporting was sparse and inconsistent, and because the population blended cardiac and cerebrovascular patients, the finding cannot be directly transferred to pure stroke care without further validation.

The authors are explicit about what this means for practice. Viscoelastic assays, they conclude, may be most appropriately used as adjunctive diagnostic and prognostic tools in neurocritical care rather than as standalone guides for transfusion or hemostatic treatment decisions in brain trauma and aneurysmal hemorrhage. The finding challenges a seductive assumption, one that has driven adoption in trauma and cardiac surgery, that simply identifying a coagulation disturbance and acting on it automatically improves outcomes. In the neurocritical setting, the leap from detection to benefit has not yet been demonstrated in rigorous trials, and current clinical guidelines accordingly do not recommend routine viscoelastic testing in these populations.

Several structural obstacles help explain the gap between prognostic promise and therapeutic proof. Included studies frequently came from single centers using institution-specific protocols, with inconsistent assay platforms, variable clinical cutoffs, and differing transfusion and antiplatelet practices. Without harmonized thresholds and standardized definitions of what counts as an actionable abnormality, clinicians cannot translate an abnormal tracing into a uniform treatment decision, and trialists cannot pool results meaningfully. These limitations reduce generalizability and complicate the interpretation of every association reported to date.

The research agenda that follows is clear. The authors call for large prospective neuro-specific cohorts using standardized viscoelastic thresholds, randomized trials testing VHA-guided transfusion or reversal strategies specifically in traumatic brain injury and subarachnoid hemorrhage, harmonization of assay parameters and clinical definitions, mechanistic studies linking viscoelastic abnormalities to neurovascular pathophysiology, and targeted evaluation of TEG-guided antiplatelet therapy in stroke populations alone. Until that work is done, the review suggests, clinicians and policymakers should read abnormal viscoelastic findings as important prognostic information, valuable for risk stratification and communication, while resisting the temptation to build treatment algorithms on evidence that has yet to bear their weight. For a technology that has already transformed hemostasis management in trauma and cardiac surgery, neurocritical care remains the unfinished frontier.

Subject of Research: Viscoelastic hemostatic assays for prognosis and treatment guidance in neurocritical illness

Article Title: The utility of viscoelastic hemostatic assays in neurocritical illness

Article References: Msheik, A., Peralta, R., Al-Rumaihi, G., Rizoli, S., Al Mokdad, Z., de Oliveira Manoel, A. L., & Al-Thani, H. (2026). The utility of viscoelastic hemostatic assays in neurocritical illness. Journal of Emergency and Disaster Medicine, 2(1), Article 10. https://doi.org/10.1007/s44467-026-00012-1

Image Credits: AI Generated

DOI: 10.1007/s44467-026-00012-1

Keywords: viscoelastic hemostatic assays, thromboelastography, ROTEM, traumatic brain injury, subarachnoid hemorrhage, ischemic stroke, coagulopathy, neurocritical care, umbrella review, antiplatelet therapy, delayed cerebral ischemia, GRADE evidence