Detection and Interpretation of Impossible and Improbable Coma Recovery Scale-Revised Scores

Objective: To determine the frequency with which specific Coma Recovery Scale-Revised (CRS-R) subscale scores co-occur as a means of providing clinicians and researchers with an empirical method of assessing CRS-R data quality.

Design: We retrospectively analyzed CRS-R subscale scores in hospital inpatients diagnosed with disorders of consciousness (DOCs) to identify impossible and improbable subscore combinations as a means of detecting inaccurate and unusual scores. Impossible subscore combinations were based on violations of CRS-R scoring guidelines. To determine improbable subscore combinations, we relied on the Mahalanobis distance, which detects outliers within a distribution of scores. Subscore pairs that were not observed at all in the database (ie, frequency of occurrence=0%) were also considered improbable.

Setting: Specialized DOC program and university hospital.

Participants: Patients diagnosed with DOCs (N=1190; coma: n=76, vegetative state: n=464, minimally conscious state: n=586, emerged from minimally conscious state: n=64; 794 men; mean age, 43±20y; traumatic etiology: n=747; time postinjury, 162±568d).

Interventions: Not applicable.

Main outcome measure: Impossible and improbable CRS-R subscore combinations.

Results: Of the 1190 CRS-R profiles analyzed, 4.7% were excluded because they met scoring criteria for impossible co-occurrence. Among the 1137 remaining profiles, 12.2% (41/336) of possible subscore combinations were classified as improbable.

Conclusions: Clinicians and researchers should take steps to ensure the accuracy of CRS-R scores. To minimize the risk of diagnostic error and erroneous research findings, we have identified 9 impossible and 36 improbable CRS-R subscore combinations. The presence of any one of these subscore combinations should trigger additional data quality review.