Adaptive interventions should include components that aim to prevent missing data on tailoring variables; and they should guide how to make intervention decisions when a tailoring variable is missing. When a tailoring variable (value) is missing, intervention options available to the clinician include (i) using the last known values of the tailoring variable to decide the patient’s current status, (ii) assuming the patient is a non-responder (or a responder) until the tailoring variable can be collected, (iii) specifying a window of time during which the tailoring variable can be collected, and/or (iv) .