The United States Preventive Services Task Force (USPSTF) published a review in JAMA regarding updated evidence on the efficacy of screening for atrial fibrillation (AF).
AF is the most frequently occurring arrhythmia. Age and AF risk are positively correlated, and patients who have AF are at elevated risk for thromboembolic stroke and mortality. In 2018, the USPSTF was unable to come to a consensus about whether older adults should be screened for asymptomatic AF by electrocardiography (ECG) due to a lack of sufficient evidence. This review, comprising 26 studies and 113,784 patients, sought to assess whether results from recent trials found clear evidence about the efficacy of AF screening programs by asking 6 key questions.
Question 1: Does selected screening for AF improve health outcomes?
One study had sufficient evidence to address this question. The fair-quality STROKESTOP study recruited adults aged 75 or 76 years in Sweden and offered ECG screening. After a median follow-up time of 6.9 years, the rate of the composite endpoint of ischemic stroke, hemorrhagic stroke, systemic embolism, hospitalization for a bleeding event, and all-cause mortality was lower among individuals who opted to receive AF screening (5.45 vs 5.68 events per 100 person-years [py]). These rates indicated that AF screening decreased risk for the composite endpoint (hazard ratio [HR], 0.96; 95% CI, 0.92-1.00; P =.045).
Question 2: Does systematic screening identify more patients with undiagnosed AF compared with usual care?
Eight trials were included in this analysis. In general, screening numerically identified more cases of AF compared with no screening (absolute risk difference range, 0.06%-0.60%; risk ratio [RR] range, 1.04-1.58). However, only 1 trial reported a significant effect. Stratified by screening method, the best performing strategies were continuous and 12-month intermittent ECG.
Question 3: What is the accuracy of selected screening tests?
Nine studies addressed this question using differing screening protocols. The accuracy of AF detection varied on the basis of screening strategy. In general, among a population with an undiagnosed AF rate of 1.3% (n=1000), AF screening protocols would identify 4 to 13 true positives, 0 to 237 false positives, 0 to 9 false negatives, and 750 to 987 true negatives.
Question 4: What are the harms of screening for AF with selected tests?
Four randomized clinical trials assessed the harms of AF screening. Compared with controls, patients who were screened by ECG had lower rates of hemorrhagic stroke (0.16 vs 0.18 events per 100 py) and hospitalization due to major bleeding (1.71 vs 1.74 events per 100 py). The trials that used continuous patch ECG reported skin irritation at a rate of 1.2% to 1.5%.
Question 5: What are the benefits of anticoagulation therapy for patients with asymptomatic, screen-detected AF?
Five trials addressed this question; however, no study was new to this review and most of the study populations had long-standing, persistent AF, not asymptomatic, screen-detected AF. Nonetheless, using warfarin over an average time of 1.5 years was associated with decreased risk for all-cause mortality (pooled RR, 0.68; 95% CI, 0.50-0.93; I2, 0%), ischemic stroke (pooled RR, 0.32; 95% CI, 0.20-0.51; I2, 0%), and severely disabling stroke (pooled RR, 0.38; 95% CI, 0.19-0.78; I2, 0%).
Question 6: What are the harms of therapy for patients with asymptomatic, screen-detected AF?
The same 5 trials included in question 5 were used to answer this question. Compared with controls, individuals using warfarin had increased risk for major bleeding events (pooled RR, 1.8; 95% CI, 0.85-3.70; I2, 0%) and for first occurrence of major bleeding (adjusted HR, 1.73; 95% CI, 1.33-2.25).
This review found that there is still a need for long-term research into whether AF screening programs are effective at identifying more cases of asymptomatic AF, ultimately decreasing risk for stroke and related morbidity and mortality. Only 1 trial was found that was designed and powered to evaluated health outcomes of AF screening. This trial, however, had no formal masking and recruited patients with known AF, which may have obscured some findings.
“Although screening can detect more cases of previously unknown AF, evidence regarding effects on health outcomes is limited,” the USPSTF stated. “Anticoagulation was associated with lower risk of first stroke and mortality but with increased risk of major bleeding, although estimates for this harm are imprecise.”
Kahwati LC, Asher GN, Kadro ZO, et al. Screening for atrial fibrillation: Updated evidence report and systematic review for the US Preventive Services Task Force. JAMA. Published online January 25, 2022. doi:10.1001/jama.2021.21811