Weighted index explained more variance in physical function than an additively scored functional comorbidity scale

Abstract 

Objective

1) examine association between the Functional Comorbidity Index (FCI) and discharge functional status (FS); 2) examine impact of FCI on FS when added to comprehensive models; and 3) compare additive FCI with weighted FCI and list of condition variables (list).

Study Design and Setting

Patients were drawn from Focus On Therapeutic Outcomes, Inc. (FOTO) database (1/1/06–12/31/07). FS collected using computer adaptive tests. Linear regression examined association between FCI and FS. Three methods of including functional comorbidities (FC) were compared.

Results

Relationship between FCI and FS varied by group (range, 0.02–0.9). Models with weighted index or list had similar R². Weighted FCI or list increased R² of crude models by <0.01 for cervical, shoulder, and lumbar; by 0.01 for wrist/hand, knee, and foot/ankle; by 0.02 for hip; by 0.03 for elbow; and by 0.08 for neurological. Addition of FCI to comprehensive models added <0.01 to R² (all groups). Weighted FCI increased R² by <0.01 for cervical, lumbar, and shoulder; by 0.01 for wrist/hand, hip, knee, and foot/ankle; by 0.02 for elbow; and by 0.04 for neurological; whereas list increased R² by <0.01 for cervical, shoulder, and lumbar; by 0.01 for knee and foot/ankle; by 0.02 for elbow, wrist/hand, and hip; and by 0.05 for neurological.

Conclusion

List of comorbidities or weighted FCI is preferable to using additive FCI.

Keywords: Risk adjustment, Comorbidity, Outcome assessment (health care), Rehabilitation, Physical therapy, Research design, Computerized adaptive testing