title: A functional diagnostic complexity index for rehabilitation medicine: measuring the influence of many diagnoses on functional independence and resource use.
abstract: 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.
authors.affiliation: Department of Rehabilitation Medicine, University of Pennsylvania, Philadelphia 19104-2676, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Stineman
authors.forename: R N
authors.initials: RN
authors.lastname: Ross
authors.forename: S V
authors.initials: SV
authors.lastname: Williams
authors.forename: J E
authors.initials: JE
authors.lastname: Goin
authors.forename: C V
authors.initials: CV
authors.lastname: Granger
mesh_terms: 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