Comparing indices of responsiveness for the Coma Near-Coma Scale with and without pain items: An Exploratory study

This study aimed to establish the indices of responsiveness for the Coma/Near-Coma (CNC) scale without (8 items) and with (10 items) pain test stimuli. A secondary purpose was to examine whether the CNC 8 items and 10 items differ when detecting change in neurobehavioral function.

We analyzed CNC data from three studies of participants with disorders of consciousness: one observational study and two intervention studies. We generated Rasch person measures using the CNC 8 items and CNC 10 items for each participant at two time points 14 ± 2 days apart using Rasch Measurement Theory. We calculated the distribution-based minimal clinically important difference (MCID) and minimal detectable change using 95% confidence intervals (MDC₉₅ ).

We used the Rasch transformed equal-interval scale person measures in logits. For the CNC 8 items: Distribution-based MCID 0.33 SD = 0.41 logits and MDC₉₅  = 1.25 logits. For the CNC 10 items: Distribution-based MCID 0.33 SD = 0.37 logits and MDC₉₅  = 1.03 logits. Twelve and 13 participants made a change beyond measurement error (MDC₉₅ ) using the CNC 8-item and 10-item scales, respectively.

Our preliminary evidence supports the clinical and research utility of the CNC 8-item scale for measuring the responsiveness of neurobehavioral function, and that it demonstrates comparable responsiveness to the CNC 10-item scale without administering the two pain items. The distribution-based MCID can be used to evaluate group-level changes while the MDC₉₅ can support clinical, data-driven decisions about an individual patient.