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.