A functional diagnostic complexity index for rehabilitation medicine: measuring the influence of many diagnoses on functional independence and resource use.
OBJECTIVE
To develop an index that weights diagnostic information (International Classification of Diseases, 9th revision, Clinical Modification, or ICD-9-CM codes) by the extent to which it is expected to affect functional status and inpatient rehabilitation length of stay (LOS).


METHODS
Eleven nationally prominent physiatrists assigned ICD-9-CM codes to ordinal categories by expected effect on functional recovery. A resulting functional diagnostic complexity index score was calculated for each patient by combining the ranked values of each ICD-9-CM code in the discharge record. Analyses were stratified across the 20 rehabilitation impairment categories (RICs) of the Functional Independence Measure-Function Related Groups.


METHODS
Patients (182,254) discharged from 465 inpatient rehabilitation units in larger hospitals and free-standing rehabilitation hospitals in 1995.


RESULTS
High degrees of diagnostic complexity were associated with low levels of functional independence at admission within each of 20 RICs (Spearman R = .06 to .25). Depending on RIC, patients in the highest (compared with the lowest) complexity category had up to a 35% increase in rehabilitation LOS after accounting for the primary medical reason for rehabilitation and severity of disabilities at admission.


CONCLUSIONS
This prototype index of medical complexity offers a promising approach for analyzing the cumulative effects of diagnoses on patients' initial functional status and rehabilitation LOS.
Stineman
M G
MG
Department of Rehabilitation Medicine, University of Pennsylvania, Philadelphia 19104-2676, USA.
Ross
R N
RN
Williams
S V
SV
Goin
J E
JE
Granger
C V
CV
D000203:Activities of Daily Living / Q000145:classification*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012046:Rehabilitation / Q000706:statistics & numerical data; D012047:Rehabilitation Centers; D016896:Treatment Outcome