At mayo clinic i tested positive for anti dsdna. latest test says negative (l) dsdna. if positive are you always positive?

Depends on lab: A lot of this depends on what your problems are. Specifically however laboratory studies can sometimes cause conflict. It depends on whether the test was done the correct way, and lab tests can vary even day today. Some labs do a better job than others. This may also depend on the technique of the type of dna test that was done. Your physician can help clarify this.