The Power of Patch Testing With Peggy Wu, MD

Peggy Wu/UC Davis Health

Peggy Wu, MD, MPH, FAAD and professor of clinical dermatology at University of California Davis has been attending the American Academy of Dermatology (AAD) Annual Meeting since she first started practicing nearly 15 years ago. This year, she is part of 3 sessions at the meeting in New Orleans, Louisiana. Wu answered questions about her sessions with Dermatology Times®.

Dermatology Times: You shared presentations on patch testing in two different sessions, “What to Do When Patch Testing is Negative” and “Contact Dermatitis.” What should your colleagues know about patch testing?

Wu: Patch testing is a very necessary tool in a general dermatologist’s armamentarium. A patch tester is your friend and something you can always refer to because when you think about rashes, and you're trying to figure out what exactly is happening, allergic contact dermatitis is definitely a very common possibility and something that you cannot diagnose unless you're looking for it. You can't really give people good advice on what to do or what to avoid because it's very personalized and very specific to the individual. You can't really do that without patch testing. We have great medications now for dermatitis, but they are not specific for allergic contact dermatitis.There are definitely cases where people have terrible atopic dermatitis and allergic contact dermatitis.The atopic dermatitis gets better, but the allergic contact dermatitis does not. Effectively, the patient does not feel like they are that much better. So, it's important to consider and the results can be very impactful.

Dermatology Times: How important is it to ask for a patient's regimen with medications and lifestyle when you consider patch testing?

Wu: I think the patient history is a huge component.Just because a person comes in for patch testing doesn't mean they have allergic contact dermatitis. I think if you look at the data for the largest consortium of patch testers, it's about 60% will actually come out with a diagnosis of allergic contact dermatitis. So, it's still important to take that history of what a person is taking medication wise, what other symptoms they're having, and previous history of rashes. All of that contributes to that pretest probability whether or not somebody might have allergic contact dermatitis and that's one lens through which you would then gauge the results and fit this into their entire skin health picture.

It's hard to predict what a person will be allergic to. There have been studies showing that, you know, we can't really predict.We can only say this might be allergic contact dermatitis, and you should get patch testing. I always look forward to the final patch test reading day, because you just never know what a person is going to have. But I would say a general trend is, ‘the more things people use, the more likely they are to have developed an allergy,’ just in terms of number of personal care products. There are definitely lists every year that the American Contact Dermatitis Society develops of common allergens, and you can ask patients to preemptively avoid the top 10 allergens like nickel and fragrance. Soyou can go down that list and try that. It does become pretty onerous to the patient. And at some point, just having the patch tests done may be the easier step.

Dermatology Times: You are also part of the “Catching Up on Clinical Guidelines” forum. Tell us about your role.

Wu: This is going to be the first year that we have this focus session. The idea was conceived out of both wanting clinicians to understand what the process is for the AAD to create clinical guidelines. There's a lot of work that goes into it. Then, we will also provide some updates on current guidelines. I've been on the clinical guidelines committee for 5 years and chair of it for the last 2. It’s a privilege to fill that role.

There have been some efforts to expedite our guidelines to have them at a rigor comparable to any other medical specialty, including larger ones. With the new methodology, workgroup size, and regulations,have updated clinical guidelines on actinic keratosis, atopic dermatitis, and a little bit on acne as well.

Dermatology Times: How often should those guidelines be checked and updated?

We try to keep our guidelines updated every 5 years. That's a process that we're trying to optimize at the moment. We recently underwent a needs assessment in which we surveyed our members, some key stakeholders, as to what topics they would like to see prioritized. That was just recently completed. We still have to present all this to the board and get official approval.

I think that these guidelines we’ve written now have the rigor of international and national standards. We are also doing annual sort of scoping updates, looking at the literature and how things how fast things are moving to figure out what we should address sooner rather than later. We've also started a new process of doing more focused and interim updates, whereas maybe not the whole guideline is updated, but only parts of it depending on the need. So, I think I want AAD members to know that our guidelines are a resource to them that we are always trying to listen and know what is important to them.