Isolated Chronically Elevated D-dimer

I [Geo] have had a number of questions from people who report a chronically elevated D-dimer with no clinical associations or parallel positive laboratory assays. In many cases their original D-dimer was ordered in response to a clinical indication such as chest pain or possible C19 symptoms, and remained elevated long after the original event had been resolved. Naturally, the correspondents worry about some lurking thrombotic event or other condition, in part because we often are not able to offer a conclusive explanation. To respond consistently, I drafted the attached document that attempts to explain the possible causes for the prolonged D-dimer results. You may find this useful, as I suspect many of us are getting this question. Please read it at your leisure and offer your comments.