Early detection of non-ambulatory survivors six months after stroke

 I wonder why they don't use an objective damage diagnosis to make a prediction.
http://www.naric.com/research/rehab/record.cfm?search=2&type=all&criteria=J64204&phrase=no&rec=119300
Abstract: Study assessed the ability of the Trunk Control Test (TCT), administered at 14 days after a stroke, to predict ambulation and motor outcome at 6 months after stroke occurrence. Sixty-eight stroke survivors were prospectively studied from the second week to the sixth month post stroke. Sex, age, stroke type, urinary incontinence, National Institutes of Health Stroke Scale (NIHSS), and TCT scores were taken as independent variables. Gait ability and motor functional outcome were assessed at 6 months post-stroke. Age, sex, urinary incontinence, TCT and NIHSS were significantly related to final modified Rankin Scale score, the motor portion of the Functional Independence Measure (FIM), and the Berg Balance Scale. Age and early TCT alone accounted for 61.1 percent of the variance in the motor FIM rating (at 6 months post-stroke). TCT less than or equal to 50 on day 14 predicts non-independent walkers. The results indicate that early administered TCT is a strong predictor of independent walking ability and motor functional outcome at six months post-stroke.