Lies, damned lies and diagnoses: Estimating the clinical utility of assessments of covert awareness in the vegetative state

Background: Functional neuroimaging of patients in the vegetative state has been shown to provide diagnostic and prognostic information beyond that which conventional behavioural assessments may allow. However, before these promising approaches may reach large numbers of patients through a standard clinical protocol, it is necessary to determine the utility of these assessments-i.e. the accuracy of their diagnoses. Methods and results: This study demonstrated that, due to the nature of statistical testing and the absence of a 'ground truth' of consciousness, it is impossible to calculate the conventional measures of clinical utility-sensitivity and specificity-for diagnoses made on the basis of functional neuroimaging for command-following. Nevertheless, it is crucial for such measures to be determined in order for valuable clinical resources to be distributed wisely. Therefore, a number of alternative guidelines are offered for the estimation of clinical utility. Conclusions: By evaluating new and existing functional neuroimaging methods against the proposed guidelines, this study argues that it may be possible to achieve dramatically and efficiently improved diagnostic and prognostic accuracy for all vegetative state patients.