Blood Levels of GFAP Improves Sensitivity of Clinical Decision Rules for Concussion 

The Food and Drug Administration (FDA) approved combined blood test to detect intracranial lesions after mild to moderate traumatic brain injury (MTBI). A new study, data collected from March 16, 2010 to March 5, 2014 and analyzed on August 11, 2021, shows that use of this blood test significantly improves the sensitivity of clinical decision rules, especially the glial fibrillary acidic protein (GFAP) level, independent from UCH-L1. Participants in the study were evaluated within 4 hours of injury and data forms were completed for each clinical decision rule before the participants’ CT scans.

Different cutoff values of GFAP with UCH-L1 reduced both sensitivity and specificity. The Canadian CT Head Rule (CCHR), the New Orleans Criteria (NOC), and GFAP plus UCH-L1 biomarkers had equally high sensitivities and CCHR had the highest specificity. The CCHR and GFAP had the highest diagnostic performance when combined.

Using combined GFAP and UCH-L1 levels with cutoffs at 67 and 189 pg/mL, respectively, sensitivity was 100% (95%CI, 82%-100%) and specificity was 25%(95%CI, 20%-30%). Negative predictive value (NPV) was 100%; with GFAP and UCH-L1 level cutoffs at 30 and 327 pg/mL, respectively; sensitivity was 91% (95%CI, 70%-98%), specificity was 20%(95%CI, 16%-24%), and NPV was 97%.

In the analysis, 349 (93%) participants, mean age 40 years, had a CT scan performed for evaluation. The number of participants that were men was 230 (66%); 314 (90%) had a Glasgow Coma Scale score of 15, and 23 (7%) had positive CT findings for concussion.