Uptake of direct oral anticoagulants in primary care: an ecological and economic study

SAIL study of stroke, systemic embolism and bleeding outcomes with warfarin anticoagulation in non-valvular atrial fibrillation (S4-BOW-AF)

Aims

In patients with non-valvular atrial fibrillation (NVAF) prescribed warfarin, the association between guideline defined international normalised ratio (INR) control and adverse outcomes in unknown. We aimed to (i) determine stroke and systemic embolism (SSE) and bleeding events in NVAF patients prescribed warfarin; and (ii) estimate the increased risk of these adverse events associated with poor INR control in this population.

Methods and results

Individual-level population-scale linked patient data were used to investigate the association between INR control and both SSE and bleeding events using (i) the National Institute for Health and Care Excellence (NICE) criteria of poor INR control [time in therapeutic range (TTR) <65%, two INRs <1.5 or two INRs >5 in a 6-month period or any INR >8]. A total of 35 891 patients were included for SSE and 35 035 for bleeding outcome analyses. Mean CHA₂DS₂-VASc score was 3.5 (SD = 1.7), and the mean follow up was 4.3 years for both analyses. Mean TTR was 71.9%, with 34% of time spent in poor INR control according to NICE criteria.SSE and bleeding event rates (per 100 patient years) were 1.01 (95%CI 0.95-1.08) and 3.4 (95%CI 3.3-3.5), respectively, during adequate INR control, rising to 1.82 (95%CI 1.70-1.94) and 4.8 (95% CI 4.6-5.0) during poor INR control.Poor INR control was independently associated with increased risk of both SSE [HR = 1.69 (95%CI = 1.54-1.86), P < 0.001] and bleeding [HR = 1.40 (95%CI 1.33-1.48), P < 0.001] in Cox-multivariable models.

Conclusion

Guideline-defined poor INR control is associated with significantly higher SSE and bleeding event rates, independent of recognised risk factors for stroke or bleeding.

Prescribing of direct oral anticoagulants and warfarin to older people with atrial fibrillation in UK general practice: a cohort study

BACKGROUND

Anticoagulation for stroke prevention in atrial fibrillation (AF) has, historically, been under-used in older people. The aim of this study was to investigate prescribing of oral anticoagulants (OACs) for people aged ≥ 75 years in the UK before and after direct oral anticoagulants (DOACs) became available.

METHODS

A cohort of patients aged ≥ 75 years with a diagnosis of AF was derived from the Clinical Practice Research Datalink (CPRD) between January 1, 2003, and December 27, 2017. Patients were grouped as no OAC, incident OAC (OAC newly prescribed) or prevalent OAC (entered study on OAC). Incidence and point prevalence of OAC prescribing were calculated yearly. The risk of being prescribed an OAC if a co-morbidity was present was calculated; the risk difference (RD) was reported. Kaplan-Meier curves were used to explore persistence with anticoagulation. A Cox regression was used to model persistence with warfarin and DOACs over time.

RESULTS

The cohort comprised 165,596 patients (66,859 no OAC; 47,916 incident OAC; 50,821 prevalent OAC). Incidence of OAC prescribing increased from 111 per 1000 person-years in 2003 to 587 per 1000 person-years in 2017. Older patients (≥ 90 years) were 40% less likely to receive an OAC (RD -0.40, 95% CI -0.41 to -0.39) than younger individuals (75-84 years). The likelihood of being prescribed an OAC was lower with a history of dementia (RD -0.34, 95% CI -0.35 to -0.33), falls (RD -0.17, 95% CI -0.18 to -0.16), major bleeds (RD -0.17, 95% CI -0.19 to -0.15) and fractures (RD -0.13, 95% CI -0.14 to -0.12). Persistence with warfarin was higher than DOACs in the first year (0-1 year: HR 1.25, 95% CI 1.17-1.33), but this trend reversed by the third year of therapy (HR 0.75, 95% CI 0.63-0.89).

CONCLUSIONS

OAC prescribing for older people with AF has increased; however, substantial disparities persist with age and co-morbidities. Whilst OACs should not be withheld solely due to the risk of falls, these results do not reflect this national guidance. Furthermore, the under-prescribing of OACs for patients with dementia or advancing age may be due to decisions around risk-benefit management.

TRIAL REGISTRATION

EUPAS29923 . First registered on: 27/06/2019.