A study of the internal construct and predictive validity of the SMART assessment for emergence from vegetative state

ABSTRACT

Objective: The Sensory Modality Assessment and Rehabilitation Technique (SMART) was developed to assess the levels of awareness, functional, sensory and communicative abilities of adults in vegetative (VS) or minimally-conscious states following severe brain injury. The current study seeks to ascertain if a total score can be derived from the individual assessments contained within SMART and to test the internal construct and predictive validity of that total score.

Subjects: Persons in VS were recruited over a 3-year period and current status was determined after a 17-year follow-up.

Design: Data were evaluated by fit to the Rasch model. Predictive validity for emergence from VS was ascertained through an Area-Under-the-Curve [AUC] analysis.

Results: Sixty people in VS were assessed on several occasions. Average age on admission was 38.8 years; 30 had anoxic brain damage; 21 traumatic injury. The Rasch analysis indicated the raw score was a sufficient statistic for awareness. Over half [55%] failed to emerge from VS. For those with anoxic brain injury, a SMART cut point of 85 gave an AUC of 0.966 (95% CI = 0.910–1.00) for emergence, as did a cut point of 68 for those with traumatic brain injury.

Discussion: The current analysis suggests that SMART may have important predictive attributes for emergence (or lack thereof). No change in status of those discharged in VS has been reported to this present day.

KEYWORDS:

• Vegetative state
• minimally conscious state
• Rasch
• SMART

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.