For example, if you had a life-threatening anaphylactic reaction to peanuts but the food allergy test was negative, it would not necessarily mean you could resume eating peanuts. You would have to eat peanuts in a safe and controlled setting, like the allergist's office, to see if anaphylaxis was really due to peanuts. A very positive test would negate the need to have an oral challenge.
On the other hand, if you presented to the allergist with symptoms such as headache or abdominal pain and tests to see if foods were the cause were negative, you could reasonably conclude that food allergy was not the reason for your complaints.
Lastly, if you have had no new symptoms in the intervening five years, you can rely on the previous tests.