Can bacterial sinus /throat infection, not yet treated, cause elevated cea? labcorp high norm = 3.9. my usual 2.7 - 3.1. reading was 4.4 that day.

No, but your CEA is: CEA levels below 5 ng are considered normal. It is test which we do not like to do unless patient has an established diagnosis of cancer. Infections do not increase the CEA level. You can safely ignore your CEA value of 4.4. Small variation in levels are common, so it can be safely ignored. Only when CEA level rises by 100% and progressively increases, do we take notice of this test.