Analysis of medical and pharmacy claims
Identification of the AF population took place in administrative medical and pharmacy databases. The medical claims were characterized for emergency room (ER) visits (using revenue codes and outpatient flag), hospital admissions (using facility type code and inpatient flag), office visits (new and established using CPT or ‘Current Procedural Code’ codes and outpatient flag), and outpatient observation under physician monitoring (using CPT codes, outpatient flag, with exclusion of ER revenue codes). These healthcare service types are fast becoming the most common criteria in identifying AF cases. The aforementioned claims were additionally identified using ICD 10 primary and secondary diagnosis codes designated for atrial fibrillation and flutter (I480, I481, I482, I483, I484, I4891, I4892). The outpatient procedures were predominantly identified using CPT codes. All claims for AF primary and secondary diagnoses were also analyzed without the specification of type of healthcare service rendered. Patient duplication is eliminated when using the combined medical as well as the integrated medical and pharmacy data.
The pharmacy claims were analyzed for oral anticoagulant medications (warfarin, direct oral anticoagulants (DOACs)) and rhythm control medications (i.e., amiodarone, disopyramide, dofetilide, dronedarone, flecainide, mexiletine, procainamide, propafenone, quinidine gluconate, quinidine sulfate), with exceptions as previously noted in Tu et al(4). The process of preparing and analyzing medical and pharmacy claims are detailed in suppl fig S1. Each medication was analyzed using both NDC (National Drug Code) and GPI (Generic Product Identifier) codes. This is because NDCs can be ambiguous and many can exist for a single product, leading to inaccuracies in the dispensing of drugs. Therefore, GPI was used to ensure consistency, with many (from NDC) to one (to GPI) mapping.
The details of healthcare service and medication types and codes used in this study are provided in suppl table S1. The exceptions for the use of anticoagulants and rhythm control, which are not applicable to atrial fibrillation/flutter, are provided in supplemental table S2.