Clinical paper A pilot study of methods for prediction of poor outcome by head computed tomography after cardiac arrest

Introduction: In Sweden, head computed tomography (CT) is commonly used for prediction of neurological outcome after cardiac arrest, as rec-ommended by guidelines. We compare the prognostic ability and interrater variability of routine and novel CT methods for prediction of poor outcome.Methods: Retrospective study including patients from Swedish sites within the Target Temperature Management after out-of-hospital cardiac arrest trial examined with CT. Original images were assessed by two independent radiologists blinded from clinical data with eye-balling without pre -specified criteria, and with a semi-quantitative assessment. Grey-white-matter ratios (GWR) were quantified using models with 4-20 manually placed regions of interest. Prognostic abilities and interrater variability were calculated for prediction of poor outcome (modified Rankin Scale 4- 6 at 6 months) for early (<24 h) and late (>= 24 h) examinations.Results: 68/106 (64 %) of included patients were examined < 24 h post-arrest. Eye-balling predicted poor outcome with 89-100 % specificity and 15-78 % sensitivity. GWR < 24 h predicted neurological outcome with unsatisfactory to satisfactory Area Under the Receiver Operating Character-istics Curve (AUROC: 0.54-0.64). GWR >= 24 h yielded very good to excellent AUROC (0.80-0.93). Sensitivities increased > 2-3-fold in examina-tions performed after 24 h compared to early examinations. Combining eye-balling with GWR < 1.15 predicted poor outcome without false positives with sensitivities remaining acceptable.Conclusion: In our cohort, qualitative and quantitative CT methods predicted poor outcome with high specificity and low to moderate sensitivity. Sensitivity increased relevantly after the first 24 h after CA. Interrater variability poses a problem and indicates the need to standardise brain CT evaluation to increase the methods' safety.