A false positive (or negative) result from an individual animal not resulting from technique errors will continue to occur on multiple tests of the same type. Therefore, the false result is usually caused by some unique characteristics of the particular animal, as opposed to a defective test. This characteristic could be a component of the animal�s blood, which is able to react in a test�s system to show a positive result in the absence of heartworm antigens or a negative result in the presence of heartworm antigens.