SNAP AF-52: Dose Appropriateness and Adherence to Oral Anticoagulation in Adults ≥65 With Atrial Fibrillation in Primary Care (Ordu, Türkiye)

SNAP AF-52 - An Ambidirectional Observational Study to Assess Label-Concordant Dosing and Medication Adherence (Proportion of Days Covered) for Oral Anticoagulants in Adults Aged ≥65 Years With Atrial Fibrillation Managed in Family Health Centers in Ordu, Türkiye, With Same-Day Tertiary Cardiology Referral for Unsafe Findings

SNAP AF-52 is an ambidirectional observational registry conducted in family health centers (primary care) across Ordu, Türkiye, enrolling adults ≥65 years with a pre-existing diagnosis of atrial fibrillation. The study assesses (a) label-concordant dosing of oral anticoagulants (DOACs/warfarin) using drug-specific criteria, and (b) medication adherence via Proportion of Days Covered (PDC) over the prior 12 months (good adherence defined as PDC ≥80%). Unsafe findings (e.g., suspected under-/overdosing, critical drug-drug interactions, very low renal function) trigger same-day referral to tertiary cardiology for evaluation and management. The retrospective window is Dec 1, 2024-Nov 30, 2025; the prospective single-visit inclusion window is Dec 1, 2025-May 31, 2026. No experimental treatment is administered; all care is routine.

Family physicians will screen their ≥65-year attendees with documented AF and record a minimum dataset during a single routine visit: demographics, body weight, most recent serum creatinine (date/value) to compute Cockcroft-Gault creatinine clearance (CrCl), current oral anticoagulant and regimen, common interacting drugs, and pharmacy dispensing dates with days' supply for the last 12 months. The system auto-classifies dose appropriateness per drug label criteria (including apixaban reduction rules; rivaroxaban/dabigatran/edoxaban CrCl thresholds and P-gp/CYP3A4 interactions) and computes PDC with carry-over of early refills; primary nonadherence is defined as no fill within 30 days of the first prescription. Retrospective capture of events includes ischemic stroke/TIA/systemic embolic event (SEE) and hemorrhagic stroke/ISTH major bleeding, plus on-treatment status at the event date.

Participants with potentially unsafe dosing or clinically high-risk interaction (e.g., strong inducers; strong dual inhibitors) or CrCl <15 mL/min are same-day referred to tertiary cardiology. Identifiable data will be stored securely per ethics approval and Turkish data protection (KVKK); only aggregated results will be reported.

Inclusion Criteria:

• Age ≥65 years.
• Established atrial fibrillation (any type) documented in the medical record.
• Presenting to a family health center (primary care) in Ordu province during the prospective window or having records within the retrospective window.
• On an oral anticoagulant (DOAC) at any time in the 12-month window.

Exclusion Criteria:

• Mechanical prosthetic heart valve or moderate-to-severe rheumatic mitral stenosis
• Participation in an interventional drug study affecting anticoagulation
• Lack of minimal data elements required for dose classification (age, sex, body weight, serum creatinine with date, current OAC and regimen)
• Investigator judgment that reliable data cannot be obtained from records