Standard CTC assays can produce false positives because non-cancer patients can have circulating cells that express tumor markers but not white blood cell markers, and these cells have normal genomes.

“even non-cancer patients can have circulating cells that look like circulating tumor cells using the markers that are generally used which are usually when you know when it's looking for certain tumor cells most assays uh look use uh stain the cells meaning they they look for markers on the cells uh and they want the cells to not express markers from lymphocytes from white blood cells so there's a marker you know that's highly expressed on white blood cells that should not be expressed on the circling tumor cell which which one do you use cd3 people usually use cd45 is the most common marker which is sort of a pan white blood cell marker and then for um on the flip side for a positive marker what is should be expressed in the cancer cell but not the white blood cells um they look for things like cytokeratins which are those you know structural proteins that that are specific to epithelial cells um but as we and others have found healthy patients can also have cells that have cytokeratin expression but no white blood cell marker expression in the circulation and other people have gone further to do single cell sequencing of those to show that their genomes are actually normal those cells have normal genomes they're not mutated like the cancer cells are”