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Table 1 Description of comorbidity measures

From: Predictive performance of comorbidity measures in administrative databases for diabetes cohorts

Measure

Definition

Data Source

Variable Categories for the Predictive Modela

Number of diagnoses

Identifies number of diagnosis codes, to the third digit. Minimum score is 0 and there is no maximum

Hospital records and physician billing claims

0−2 (reference), 3–5, 6–9, 10 or more

Charlson index

Summarizes diagnoses for 17 conditions. Total score can range from 0 to 32

Hospital records and physician billing claims

0−1 (reference), 2–3, 4–5, 6 or more

Elixhauser index

Captures diagnoses for 31 conditions. No total score is produced

Hospital records and physician billing claims

Dummy variables (0 = absent; 1 = present) are used to define the 31 conditions

Number of drugs

Identifies number of prescription drugs using six-digit AHFS codes. Total score can range from 0 to 125

Prescription drug records

0−1 (reference), 2–3, 4–5, 6 or more

Chronic Disease Score (CDS)

Uses AHFS codes to identify number of different prescriptions for treating 17 conditions. Total score can range from 0 to 35

Prescription drug records

0−1 (reference), 2–3, 4–5, 6–7, 8 or more

  1. aVariable categories were defined based on previous research and by examining the frequency distributions for each of the comorbidity measures. Cut-points for the categories were created to minimize sparse cell sizes, AHFS American Hospital Formulary System.