"Negative" is the Engpsh word used to describe a test result that is free of the substance or condition being tested for. In this case, "nucleic acid test negative" means that the person tested did not have a detectable amount of nucleic acid (DNA or RNA) associated with the virus or disease in question.
An example sentence would be: "The patient's nucleic acid test results came back negative, indicating that they do not have an active infection."
Another example sentence would be: "The nucleic acid test was negative, He does not have the virus."