Navar AM, et al. - Using a cohort of patients with atherosclerotic cardiovascular disease (ASCVD), researchers performed this observational analysis to evaluate the reliability of mortality rates in the Social Security Administration Death Master File (SSDMF) for use in clinical research. They analyzed mortality data of 667,516 adults with ASCVD. The investigators noted marked underestimation of mortality rates in the SSDMF. Furthermore, the undercapture with SSDMF was variable among states and over time. Overall, these results were indicative of non-reliability of SSDMF data and should thus not be used alone by researchers to estimate mortality rates.