Table 5.

Principal Component Analysis of Quantitative CT (qCT) Predictors, Age, and GCS

	Components
Predictors	1	2	3	4	5	6	7
Age	−0.05	0.07	0.98	0.09	0.02	−0.13	0.09
GCS	0.95	−0.11	−0.06	−0.17	−0.06	0.09	−0.21
SAH/IPH volume	−0.05	0.02	0.02	0.05	0.99	0.04	0.06
SDH volume	−0.18	0.27	0.10	0.92	0.07	−0.04	0.18
EDH volume	0.08	−0.02	−0.13	−0.03	0.05	0.99	−0.03
Shift (distance)	−0.12	0.91	0.08	0.28	0.02	−0.02	0.28
Cistern effacement	−0.29	0.34	0.13	0.21	0.08	−0.04	0.86

Principal component analysis of quantitative computed tomography (qCT) predictors, age and GCS. Thick-lined boxes highlight high loading coefficients ≥0.9. Thin-lined boxes demonstrate intermediate loading coefficients from ∼0.3 up to 0.9. A principal component that is driven purely by a single predictor demonstrates a coefficient of 1.0 for a single predictor, and a coefficient of zero for all other predictors under consideration. Here, components 3, 5, and 6 were each driven almost solely (loading coefficient ≥0.98) by a single feature (age, SAH/IPH volume, and epidural hematoma volume, respectively), indicating that these predictors had little collinearity with each other or with other predictors. In contrast, components 1, 2, 4, and 7 consisted of significant contributions from more than one predictor. Components 2, 4, and 7 demonstrated covariances among features related to intracranial mass effect, including subdural hematoma volume, severity of midline shift, and severity of basal cistern effacement, and Component 1 demonstrated a negative correlation of admission GCS with severity of cistern effacement; both of these result from an entirely data-driven principal component analysis approach, yet are also intuitively satisfying.

qCT, quantitative CT; GCS, Glasgow Coma Scale; SAH, subarachnoid hemorrhage; IPH, intraparenchymal hemorrhage; SDH, subdural hematoma; EDH, epidural hematoma.