| Covariate | Definition | Coding |
|---|---|---|
| Patient characteristics | ||
| Age | Age in years | Continuous |
| Male | Male sex | Dichotomous (yes/no) |
| Medicare supplemental | Enrollment in a private health insurance in addition to Medicare | Dichotomous (yes/no) |
| Medicare Advantage | Managed health care – PPO or HMO | Dichotomous (yes/no) |
| Region of residence | Region of residence at index date | Categorical (Northeast, Midwest, West, South, missing) |
| Indexes | ||
| Comorbidity index | Deyo-Charlson Comorbidity Index | Interval (0-33) |
| CHA2DS2-VASc score | Congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, previous stroke or TIA or thromboembolism, vascular disease, age 65-74 years, sex category (female gender) | (1 point each, 2 points for age ≥ 75 years and stroke for a maximum of 9) |
| HAS-BLED score | Hypertension, abnormal liver/renal function, stroke, bleeding history, labile INR, elderly (age > 65), drugs (e.g., antiplatelet or NSAIDs) or alcohol concomitantly (1 point each). Labile INR set to missing for all patients | (1 point each for a maximum of 8) |
| Comorbid illnesses | ||
| Ischemic stroke | ICD-9-CM codes 433.01, 433.10, 433.11, 433.21, 433.31, 433.81, 433.91, 434.00, 434.01, 434.11, 434.91, 436 | Dichotomous (yes/no) |
| Hemorrhagic stroke | ICD 9-CM codes 430.x-432.x | Dichotomous (yes/no) |
| Transient ischemic attack | ICD-9-CM code 435.xx | Dichotomous (yes/no) |
| Renal insufficiency | ICD-9-CM codes 582.xx, 585.xx, 588.xx | Dichotomous (yes/no) |
| Myocardial infarction | ICD-9-CM code 410.xx | Dichotomous (yes/no) |
| Congestive heart failure | ICD-9-CM codes 402.01, 402.11, 402.91, 404.01, 404.03, 404.11, 404.13, 404.91, 404.93, 428.xx | Dichotomous (yes/no) |
| Cerebrovascular disease | ICD-9-CM codes 430.x-435.x | |
| Coronary artery disease | ICD-9-CM codes 410.xx, 411.1x, 411.8x, 412.xx, 413.xx, 414.0 x, 414.2x, 414.3x | Dichotomous (yes/no) |
| Peripheral vascular disease | ICD-9-CM codes 433.xx, 437.0x, 437.1x, 440.xx, 443.xx | Dichotomous (yes/no) |
| Cancer | ICD-9-CM codes 140.xx-239.xx, V10.xx | Dichotomous (yes/no) |
| Osteoarthritis | ICD-9-CM codes 715.xx, 721.x | Dichotomous (yes/no) |
| Diabetes mellitus | ICD-9-CM codes 250.xx AND/OR use of oral glucose-lowering medications (GPI starts with 27, except 2710 and 2730) | Dichotomous (yes/no) |
| Hypertension | ICD-9-CM codes 401.xx, 402.xx, 403.xx, 404.xx | Dichotomous (yes/no) |
| Dyslipidemia | ICD-9-CM code 272.xx OR GPI starts with 39 | Dichotomous (yes/no) |
| Pericarditis | ICD-9-CM code 420.xx | Dichotomous (yes/no) |
| Hyperthyroidism | ICD-9-CM codes 242.0x-242.9x | Dichotomous (yes/no) |
| Coagulation defect factors | ICD-9-CM codes 286.1x, 286.3x, 286.5x, 285.5x, 286.5x, 286.4x, 286.4x, 286.3x, 286.5x, 286.5x, 287.4x, 287.5x, 287.8x, 270.4x | Dichotomous (yes/no) |
| Dementia | ICD-9-CM codes 290.xx, 294.xx, 330.xx, 331.xx | Dichotomous (yes/no) |
| Parkinson’s disease | ICD-9-CM code 332.xx | Dichotomous (yes/no) |
| Gait abnormality | ICD-9-CM codes 334.xx, 781.2x | Dichotomous (yes/no) |
| Dizziness | ICD-9-CM codes 458.0 x, 780.4 x | Dichotomous (yes/no) |
| Diabetic and alcoholic neuropathy | ICD-9-CM codes 357.2x and/or 357.5x | Dichotomous (yes/no) |
| Esophageal varices | ICD-9-CM codes 456.0x-456.2x | Dichotomous (yes/no) |
| Major trauma | ICD-9-CM codes 806.xx, 808.xx, 809.xx, 820.xx, 821.xx, 822.xx, 823.xx, 824.xx, 825.xx, 826.xx, 827.xx, 828.xx, 829.xx, 835.xx, 843.xx, 901.1x, 901.2x, 901.3x, 901.83, 902.0x, 902.1x, 902.5x, 902.51, 902.52, 902.53, 902.54, 902.59, 902.87, 903.0x, 903.1x, 904.0x, 904.1x, 904.2x, 904.4x, 904.5x, 924.xx, 928.xx, 942.xx, 943.xx, 945.xx, 952.xx, 959.6x, 959.7x, 897.xx, 820.xx-929.xx | Dichotomous (yes/no) |
| Pre-index medications | ||
| Antiarrhymics | Any pharmacy claim | Dichotomous (yes/no) |
| Amiodarone | Any pharmacy claim | Dichotomous (yes/no) |
| Diuretics | Any pharmacy claim | Dichotomous (yes/no) |
| Pre-index medications | ||
| Vasopressors | Any pharmacy claim | Dichotomous (yes/no) |
| Antihyperlipidemics | Any pharmacy claim | Dichotomous (yes/no) |
| NSAIDs | Any pharmacy claim | Dichotomous (yes/no) |
| COX-2 inhibitors | Any pharmacy claim | Dichotomous (yes/no) |
| Platelet aggregation inhibitors | Any pharmacy claim | Dichotomous (yes/no) |
| Anti-inflammatory agents | Any pharmacy claim | Dichotomous (yes/no) |
| Proton pump inhibitor | Any pharmacy claim | Dichotomous (yes/no) |
| Stroke | ICD-9-CM codes for ischemic (433.01, 433.10, 433.11, 433.21, 433.31, 433.81, 433.91, 434.00, 434.01, 434.11, 434.91, 436) or hemorrhagic stroke (430.x-432.x) | Dichotomous (yes/no) |
| Arterial embolism and thrombosis | ICD-9-CM codes for 444.xx | Dichotomous (yes/no) |
| Venous thromboembolism (VTE) | Inpatient or emergency department ICD-9-CM codes for deep venous thromboembolism (451.1x, 451.2x, 451.81, 451.83, 451.84, 451.9x, 453.1x, 453.2x, 453.4x, 453.5x, 453.6x, 453.7x, 453.8x, 453.9x, 997.2x) or pulmonary embolism (415.1x) | Dichotomous (yes/no) |
| Major bleeding | ICD-9-CM codes 423.0x, 430.xx, 431xx, 432xx, 852.0x, 852.2x, 852.4x, 853.0x, 455.2, 455.5, 455.8, 456.0, 456.20, 459.0x, 530.7x, 530.82, 531.00, 531.01, 531.20, 531.21, 531.40, 531.41, 531.60, 531.61, 533.01, 533.20, 533.21, 533.40, 533.41, 533.60, 533.61, 534.00, 534.01, 534.20, 534.21, 534.40, 534.41, 534.60, 534.61, 535.11, 535.21, 535.31, 535.41, 535.51, 535.61, 537.83, 562.02, 562.03, 562.12, 562.13, 568.81, 569.3, 569.85, 578, 578.0, 578.1, 578.9, 593.81, 599.7, 719.10, 719.11, 719.12, 719.13, 719.14, 719.15, 719.16, 719.17, 719.18, 719.19, 784.7, 784.8x, 786.3x 1 inpatient claim with ICD-9-CM diagnosis codes 430.xx, 431.xx, 432.xx, 852.0x, 852.2x, 852.4x, 853.0x in any position of the claim and the remaining ICD-9-CM codes in the primary position (primary diagnosis) of the claim |
Dichotomous (yes/no) |
| Exclusions | ICD-9-CM codes 394.0x, 394.1x, 394.2x, 394.9x, 396.xx, V43.3x, Z95.2x, V42.2x, 238.4x, 238.71, 283.2x, 289.81, 289.91, 5855, 5856, | Dichotomous (yes/no) |
| Kidney transplant | ICD-9-CM codes V42.0x, 996.81 or ICD-9-CM procedure codes 55.6x or CPT codes 50340, 50360, 50365, 50370, 50380 | |
| Chronic dialysis | ICD-9-CM codes 792.5x, V56.2x or ICD-9-CM procedure codes 39.95, 54.98 or CPT codes 90935, 90937, 90945, 90947, 99512, 99601, 99602 | |
CPT = Current Procedural Terminology; GPI = Generic Product Identifier; ICD-9-CM = International Classification of Diseases, Ninth Revision, Clinical Modification; INR = international normalized ratio; NSAID = nonsteroidal anti-inflammatory drug; TIA = transient ischemic attack.