Return to recommendations Stroke risk Why the committee made the recommendations The committee decided to prioritise identifying people above or below a certain risk threshold (discrimination) in its interpretation of the evidence rather than estimating a person's risk of stroke in absolute terms. The evidence suggested that a score of 2 or more is the ideal threshold for the CHA2DS2-VASC in terms of indicating the need for anticoagulation. (Men with a CHA2DS2-VASc score of 1 were regarded as being at intermediate risk, and a group in whom anticoagulation should also be considered.) The evidence showed that this threshold of 2 or more offered a good combination of high sensitivity (0.92) and adequate specificity (0.23). The high sensitivity means that the tool would correctly identify almost everyone who would later have a stroke if they did not receive anticoagulants. Importantly, this will allow them to be prescribed anticoagulants to reduce their risk of stroke. The adequate specificity means that 23% of the people who would not later have a stroke (even when not taking anticoagulants) would be correctly identified as not needing anticoagulation. This would prevent these people from having adverse events from anticoagulants. It also means that 77% of people who would not later have a stroke (without anticoagulation) would be wrongly identified as needing anticoagulation. However, this was thought to be acceptable given the perceived lesser harms from unnecessarily giving anticoagulants compared with not giving anticoagulants to people who need them, together with the inevitable trade-off between sensitivity and specificity. The ATRIA stroke risk score was shown to have better overall accuracy, but although it had better specificity than CHA2DS2-VASc (fewer false-positive results) it had lower sensitivity, meaning that more people at risk would be missed (more false-negative results) compared with the CHA2DS2-VASc score. 