Table 1.
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 |
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.