Tau proteins in serum predict neurological outcome after hypoxic brain injury from cardiac arrest: results of a pilot study.

OBJECTIVE: To conduct a pilot study to evaluate the prognostic potential of serum tau protein measurements to predict neurological outcome 6 months following resuscitation from cardiac arrest.
METHODS: In this retrospective observational study, we employed a new ultra sensitive digital immunoassay technology to examine serial serum samples from 25 cardiac arrest patients to examine tau release into serum as a result of brain hypoxia, and probe for its significance predicting six-month neurological outcome. Serial blood samples were obtained from resuscitated cardiac arrest survivors during their first five days in an intensive care unit, and serum total tau was measured. Cerebral function assessments were made using Cerebral Performance Categorization (CPC) at discharge from the ICU and six months later. Tau data were analyzed in the context of 6-month CPC scores.
RESULTS: Tau elevations ranged from modest (<10 pg/mL) to very high (hundreds of pg/mL), and exhibited unexpected bi-modal kinetics in some patients. Early tau elevations appeared within 24h of cardiac arrest, and delayed elevations appeared after 24-48 h. In patients with delayed elevations, areas under the curves of tau concentration vs. hours since cardiac arrest were highly predictive of 6-month outcome (P<0.0005).
CONCLUSION: High-sensitivity serum tau measurements combined with an understanding of tau release kinetics could have utility for hypoxic brain injury assessment and prediction of cerebral function outcome.