In developing the 2021 secondary stroke prevention guideline, the writing group reviewed prior published AHA/ASA guidelines and scientific statements. Table 2 contains a list of these other guidelines and statements deemed pertinent to this writing effort and is intended for use as a reader resource, thus reducing the need to repeat existing guideline recommendations. 1.5. Class of Recommendation and Level of Evidence Recommendations are designated both a Class of Rec- ommendation (COR) and a Level of Evidence (LOE). The COR indicates the strength of recommendation, encom- passing the estimated magnitude and certainty of benefit in proportion to risk. The LOE rates the quality of scien- tific evidence supporting the intervention on the basis of the type, quantity, and consistency of data from clinical trials and other sources (Table 3). Numerous studies have evaluated strategies for stroke prevention in individuals without a history of stroke/TIA (ie, primary prevention studies) or included individuals with a history of stroke/TIA mixed into the pools of patients studied in smaller numbers. After care- fully reviewing the literature and discussing with AHA methodologists, the writing group decided that many of these prevention strategies were important to include Table 1. Evidence Review Committee Question Question No. Question Section No. 1 In patients with an ischemic stroke or TIA, what are the benefits and risks of DAPT compared to single antiplatelet therapy within 5 y for prevention of recurrent stroke? DAPT indicates dual antiplatelet therapy; and TIA, transient ischemic attack. CLINICAL STATEMENTS AND GUIDELINES Kleindorfer in any guideline on the prevention of recurrent stroke. There is often no reason to think that the mechanism of stroke prevention and benefits would be different in pri- mary versus secondary prevention, although not studied within a purely secondary stroke prevention trial. 