Our September, 2017 Quick Question asks, How do you assay for direct oral anti-Xa antithrombotics such as rivaroxaban? The question, provided by friend and colleague, Dave McGlasson, also applies to apixaban, betrixaban, and edoxaban, all FDA-approved oral anti-Xa antithrombotics. What has never been approved is the chromogenic anti-Xa assay, despite release of calibrators and controls with validation data by several distributors and despite countless meetings with FDA review committees. Though pharmaceutical manufacturers claim there is no need to monitor DOACs, clinical evidence and the demands of clnicians make it necessary for laboratories to offer a validated assay. The grapevine asserts that several of us, stymied by the lack of reliable assays, have begun to offer the chromogenic anti-Xa “off-label.” Included in our question is the qualiltative urine test strip, DOASENSE, which was described by Dr. Oksana Volod at the recent ASCLS meeting in San Diego. Let’s learn how many of us are using these, or other approaches. Geo.