The reliability and validity of the PALOC-s: a post-acute level of consciousness scale for assessment of young patients with prolonged disturbed consciousness after brain injury
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The objective of the study was the validation of the Post-Acute Level of Consciousness scale (PALOC-s) for use in assessing levels of consciousness of severe brain injured patients in a vegetative state or in a minimally conscious state. A cohort of 44 successively admitted patients (between 2 and 25 years of age), who were treated in an early intensive neurorehabilitation programme, were included in the study. Each patient was examined, using the Western Neuro Sensory Stimulation Profile (WNSSP) and the Disability Rating Scale (DRS), once every two weeks resulting in 327 examinations (all videotaped). To determine the reliability of the PALOC-s, six observers rated one videotape of each patient. One of the observers rated the same tapes a second time, 3-4 months later. Validity was determined by correlating 100 ratings of one observer with the scores on the WNSSP and the DRS. To determine the responsiveness of the PALOC-s, the size of change between the scores of the first and last examinations was calculated. The inter-observer correlations and agreement scores varied between .82 and .95. The intra-observer correlation and agreement scores varied between .94 and .96. Correlations with the WNSSP varied between .88 and .93, and with the DRS between .75 and .88. The responsiveness was significantly high (t=8.2), with a standardised effect size of 1.30. It is concluded that the PALOC-s is a reliable, valid, and responsive observation instrument provided it is administered after a structured assessment by an experienced and trained clinician. The PALOC-s is feasible for use in clinical management, as well as in outcome research.