Measuring complexity in neurological rehabilitation: the Oxford Case Complexity Assessment Measure (OCCAM).

Objective: To investigate validity and reliability of a new measure of case complexity, the Oxford Case Complexity Assessment Measure (OCCAM).

Design: Data collection on inpatients and outpatients attending for rehabilitation. In subsets, repeat assessments were undertaken two weeks apart, by clinicians unaware of initial data, and on admission and on discharge from inpatient rehabilitation.

Setting: Specialist neurological rehabilitation service.

Subjects: Patients receiving rehabilitation after acute onset disability.

Interventions: Assessment by clinical staff as part of routine care.

Measures: OCCAM, the INTERMED, Rehabilitation Complexity Scale - Extended (RCS-E), clinical judgement of complexity (0-10 numerical rating scale), length of stay and discharge destination (for inpatients).

Results: For the OCCAM, the Cronbach's α coefficient was 0.69 and item-total correlations were moderate to high except for pathology and time. The correlation coefficients with OCCAM were: INTERMED (ρ = 0.694), RCS-E (ρ = 0.736), and team judgement (ρ = 0.796). Inter-rater agreement was excellent (Weighted κ = 0.95). Correlation between admission and discharge scores was ρ = 0.917. Test-retest agreement was good (intraclass correlation coefficient 0.86). Higher mean admission scores were associated with prolonged stays (38.6 ± 12.2 versus 32.9 ± 13.7, P = 0.04) and failure to return home (48.0 ± 13.7 versus mean 32.1 ± 10.7, P < 0.001). The optimal cut-off of OCCAM to detect patients not discharged home was ≥ 34, with corresponding sensitivity and specificity of 84.6% and 62.8%, respectively.

Conclusions: This preliminary evidence suggests that the OCCAM may measure case complexity reliably, and may predict rehabilitation resource used and outcome. Further research is warranted.