The Office of the National Coordinator for Health Information Technology (ONC) is seeking comments on how to achieve widespread exchange of health information through interoperable certified electronic health record (EHR) technology nationwide by the end of 2018, as is called for by the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA).  MACRA also mandates that ONC establish metrics for determining the extent to which this goal has been met.  To that end, the ONC is soliciting input on the following topics:  (1) populations and components of interoperability that should be measured; (2) current data sources and potential metrics that address the MACRA requirement; and (3) other data sources and metrics ONC should consider to measure interoperability more broadly.  Comments on the notice, which will be published tomorrow, will be accepted until June 3, 2016.