PHILADELPHIA – A 32-gene screening test for stroke risk identified a subgroup of atrial fibrillation (AFib) patients with an elevated rate of ischemic strokes despite having a low stroke risk by conventional criteria by their CHA2DS2-VASc score in a post-hoc analysis of more than 11,000 patients enrolled in a recent drug trial.
Mitchel L. Zoler/MDedge News
Dr. Nicholas A. Marston
Overall, AFib patients in the highest tertile for genetic risk based on a 32 gene-loci test had a 31% increase rate of ischemic stroke during a median 2.8 years of follow-up compared with patients in the tertile with the lowest risk based on the 32-loci screen, Nicholas A. Marston, MD, said at the American Heart Association scientific sessions. This suggested that the genetic test had roughly the same association with an increased stroke risk as several components of the CHA2DS2-VASc score, such as female sex, an age of 65-74 years old, or having heart failure as a comorbidity, each of which links with an increased risk for ischemic stroke of about 31%-38%, Dr. Marston noted.
The genetic test produced even sharper discrimination among the patients with the lowest stroke risk as measured by their CHA2DS2-VASc score (Circulation. 2012 Aug 14;126[7]: 860-5). Among the slightly more than 3,000 patients in the study with a CHA2DS2-VASc score of three or less, those in the subgroup with the highest risk by the 32-loci screen had a stroke rate during follow-up that was 76% higher than those in the low or intermediate tertile for their genetic score. Among the 796 patients with a CHA2DS2-VASc score of just 1 or 2, those who also fell into the highest level of risk on the 32-loci screen had a stroke rate 3.5-fold higher than those with a similar CHA2DS2-VASc score but in the low and intermediate tertiles by the 32-loci screen.
The additional risk prediction provided by the 32-loci test was statistically significant in the analysis of the 3,071 patients with a CHA2DS2-VASc score of 3 or less after adjustment for age, sex, ancestry, and the individual components of the CHA2DS2-VASc score, which includes factors such as hypertension, diabetes, and heart failure, said Dr. Marston, a cardiologist at Brigham and Women’s Hospital in Boston. The 3.5-fold elevation among patients with a high genetic-risk score in the cohort of 796 patients with a CHA2DS2-VASc score of 1 or 2 just missed statistical significance (P = .06), possibly because the number of patients in the analysis was relatively low. Future research should explore the predictive value of the genetic risk score in patients with a CHA2DS2-VASc score of 0 or 1, the “group where therapeutic decisions could be altered” depending on the genetic risk score, he explained.
Dr. Marston and his associates used data collected in the ENGAGE AF-TIMI 48 (Effective Anticoagulation with Factor Xa Next Generation in Atrial Fibrillation–Thrombolysis in Myocardial Infarction 48) trial, which was designed to assess the safety and efficacy of the direct-acting oral anticoagulant edoxaban in patients with AFib (New Engl J Med. 2013 Nov 28; 369[21]: 2091-2104). The 32-loci panel to measure a person’s genetic risk for stroke came from a 2018 report by a multinational team of researchers (Nature Genetics. 2018 Apr;50[4]: 524-37). The new analysis applied this 32-loci genetic test panel to 11.164 unrelated AFib patients with European ancestry from the ENGAGE AF-TIMIT 48 database. They divided this cohort into tertiles based on having a low, intermediate, or high stroke risk as assessed by the 32-loci genetic test. The analysis focused on patients enrolled in the trial who had European ancestry because the 32-loci screening test relied predominantly on data collected from people with this genetic background, Dr. Marston said.
SOURCE: Marston NA et al. AHA 2019, Abstract 336.