We developed and validated the parsimonious MortalitY in Moderate-Severe TBI plus ICU-Complications (MYSTIC)-Score to predict in-hospital mortality of maximally treated msTBI patients.

Current outcome models of moderate-severe traumatic brain injury (msTBI) include only admission characteristics, lacking adjustments for early deaths, limitations-of-care, or ICU complications.

We analyzed 485 msTBI patients consecutively enrolled in the single-center prospective observational OPTIMISM-study collecting 27 pre-defined ICU complications between 11/2009-5/2019. From that cohort, 2/3 were randomly selected for the MYSTIC-Score derivation and 1/3 for internal validation. Using multivariable logistic regression, we identified independent predictors of in-hospital mortality with validated admission predictors in maximally treated patients without early (<24h) death or limitations-of-care. Based on the model’s parameter estimates, we constructed the MYSTIC-Score and tested its discrimination and calibration in both cohorts using the area-under-the-receiver-operating-characteristic-curve(AUC) and Hosmer-Lemeshow-goodness-of-fit(HL) test.

In the derivation cohort (n=324), the mean age was 50 (SD=22) years, 72% were men, and 91% were non-Hispanic/Latino. In-hospital mortality was 36%. The MYSTIC-Score ranged from 34-189, with higher scores indicating higher likelihood of mortality, and included patient’s age, ethnicity, Marshall-CT-score, motor Glasgow-Coma-Scale, pupillary reactivity, pre-hospital hypotension, hypoxia, presence of traumatic SAH or epidural hematoma (all on admission), brain edema, herniation, Systemic-Inflammatory-Response-Syndrome, sepsis, acute kidney injury, cardiac arrest, and urinary tract infection (all in ICU). The score’s discrimination and calibration were excellent (AUC=0.95; HL-p-value=0.34, with p>0.05 indicating good calibration). In the validation cohort (n=161), ROC-AUC was 0.92 with a HL-p-value=0.01. The calibration curve indicated decreased calibration in the lowest decile of the MYSTIC-Score, likely due to limited power.

The MYSTIC-Score is the first tool to predict the risk of dying in the hospital in maximally treated msTBI patients including ICU complications. Our study highlights that adding ICU-complications to hospital admission criteria strengthens outcome prediction in msTBI. External validation is pending.