These tests have an excellent negative predictive value (meaning that a negative test indicates that substance is NOT cause of the allergy). However the positive predictive value is so-so (meaning that a positive test is not always accurate). Your doctor is the best person to interpret the results.
In Addition the range of allergens used and the the technique is very important. If done incorrectly false negative and false positive may arise. Therefore it should ONLY be done by a Specialist with Allergy Training.