Comment on the Reports of Over-estimation of ASCVD Risk Using the 2013 AHA/ACC Risk Equation
To the Editor:
We read with interest the comment by Ridker and Cook in The Lancet1 on the new atherosclerotic cardiovascular disease (ASCVD) risk equation released by the American College of Cardiology and American Heart Association.2 They showed that the new risk equation overestimates ASCVD risk when applied in several cohort studies. One of these studies was the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study,3 which was used in the American College of Cardiology/American Heart Association guidelines to validate the ASCVD risk equation. As REGARDS investigators, we are writing to provide clarification on design components of REGARDS and other contemporary cardiovascular epidemiology studies cited by Ridker and Cook that could contribute to lower-than-expected event numbers. We offer 4 possible explanations for the apparent overestimation of ASCVD risk by the new equation. In our opinion, these explanations suggest that the ASCVD risk equation may be more valid than has been suggested by Ridker and Cook.
First, the studies used to develop the ASCVD risk equation included “active surveillance” to supplement self-report for identifying possible events. For example, in the Atherosclerosis Risk in Communities (ARIC) Study (1 of the studies used in developing the ASCVD risk equation), investigators identified possible ASCVD events using 2 approaches: (1) study staff telephoned participants or their proxies annually to identify hospitalizations and deaths; and (2) they searched lists of International Classification of Diseases codes from area hospitals …