Labcorp hiv 4th gen test 1 year 10 months after last exposure. what could cause the initial result to be reactive when all subsequent reflex and follow up tests for hiv 1/2 were negative?

Most likely a false + test. Discuss with lab there to get an idea of how often they get a + test that then turns negative. It might be possible you are one of the very rate HIV + with & infection that your own body clears & has cleared. Please discuss with your Dr. Recommend you contact a University Medical School HIV treatment group as they may be interested in learning about you immune system.