“…Dual Medicare–Medicaid enrollees represent a costly and vulnerable population. Research studies on duals—including studies on dual Medicaid enrollment and how it is affected by policy changes (Borella et al, 2018; Ettner, 1997; Gardner & Gilleskie, 2012; McInerney et al, 2017; Pezzin & Kasper, 2002; Ungaro & Federman, 2009), studies on the association between dual enrollment and health care utilization (Moon & Shin, 2006; Rahman, Tyler, Thomas, Grabowski, & Mor, 2015), or studies of health, disability, and service use within the dual-eligible population (Reichard & Fox, 2013)—can offer important lessons for public policy and public health. Investigations of these issues based on survey data will benefit from careful attention to the potential for misclassification of Medicaid participation and ways to address the bias arising from it.…”