Dear Dr. Roach: I recently underwent skin scratch testing for food allergies. I was shocked that among the positive findings was peanuts. I have eaten peanuts all of my life (I’m 55) and have never had any type of reaction to peanuts. I was given an EpiPen and was told to avoid peanuts.

The same skin testing results were confirmed by a second allergist. I’m afraid that avoiding peanuts will sensitize me to them when I feel that I’m currently desensitized. I do have chronic inflammation and rheumatoid arthritis, so I don’t want to ingest something that may cause an inflammatory response. Prior to the skin testing, blood tests showed a very low sensitivity to peanuts. What is your opinion on this? — L.E.

Answer: Most patients and many physicians have trouble with understanding false-positive and false-negative results. Very few (if any) medical tests are perfect, and there is an exception to nearly every rule. Some tests are very far from perfect, and scratch testing for allergies are one of these tests.

Scratch testing is sensitive; it will rarely miss a true case of a peanut allergy. But it isn’t especially specific, meaning that when it says you are positive, it might be wrong. For people in whom a peanut allergy isn’t suspected, the chance of this being a false positive becomes higher.

About 1.5% of the population has a peanut allergy. Since you have eaten peanuts your whole life and haven’t had problems, you have a lower risk than the general population. When putting the numbers into the equation (Bayes’ theorem) by using the published test characteristics for scratch testing, you have less than a 1% chance of a peanut allergy. The test is over 99% likely to be a false positive.

I wouldn’t have told you to stop eating peanuts based on the skin test results. While it is true that avoiding peanuts can lead to sensitization, this is only true in infants and young children; there’s no concern in adults.

Peanuts are not considered a pro-inflammatory food. People who frequently eat peanuts tend to have lower levels of inflammatory markers. I wouldn’t tell you to avoid peanuts from the standpoint of your RA.