Patch testing for allergic contact dermatitis with subset of allergens lowers costs

Key takeaways:

• Patch testing for allergic contact dermatitis with quaternium-15 alone captured 53% of patients to the formaldehyde group.
• Adding formaldehyde 1% as a second allergen increased capture rate to 78%.

Instead of patch testing with all allergens in any given group, using an optimized subset of allergens to test for allergic contact dermatitis can provide a similar level of care at a reduced cost, according to a study.

“Allergy to an agent can sometimes be readily detected by a single patch test. Other times, detecting allergy to an agent may require multiple different, related agents to be applied,” Ning C. McKenzie, BA, a medical student at Mayo Clinic Alix School of Medicine, and colleagues wrote. “However, when very closely related, the additional tests may not offer much additional information, and may be associated with additional cost.”

According to the authors, one such agent group that has closely related allergens is formaldehyde. As a common cause of allergic contact dermatitis, formaldehyde is found in many cosmetics and toiletries. Patch testing has shown that when a patient is allergic to one formaldehyde agent, they are usually allergic to others as well.

“At Mayo Clinic, we routinely test to nine formaldehyde-related allergens in our Standard Series, in which our recent study has shown strong potential overlap,” the authors wrote. “This study aims to investigate the cost effectiveness of performing numerous patch tests of a single representative allergen group (formaldehyde), by computationally optimizing the highest yield allergens in a sequential manner.”

In the study, 9,832 patients were tested to all listed allergens in the formaldehyde group which included formaldehyde, quaternium-15, hexahydro-1,3,5-tris(2-hydroxyethyl)triazine, diazolidinyl urea, imidazolidinyl urea, toluenesulphonamide formaldehyde resin, DMDM hydantoin and ethyleneurea melamine formaldehyde mix.

Results showed that 830 patients had positive patch tests. According to the Patch Optimization Platform, which identifies which single formaldehyde-related allergen optimally captured patients with clinically relevant allergic contact dermatitis, quaternium-15 alone captured 53% of patients to the formaldehyde group. When adding formaldehyde 1% as a second allergen, 78% of patients were captured to the formaldehyde group.

The authors identified that 94% of patients can be captured by the following five formaldehyde allergens: quaternium-15, formaldehyde 1%, hexahydro-1,3,5-tris(2-hydroxyethyl)triazine, toluenesulphonamide and either diazolidinyl urea or imidazolidinyl urea. Adding any more allergens beyond these five only yielded a 2% or less increase in benefit.

Since the incremental cost-per-additional-diagnosis increased up to 44-fold as the number of allergens tested increased, using an optimized allergen selection algorithm may be in the best interest of the patient.

“By choosing an evidence-based optimized subset of allergens, clinicians can provide a better or similar level of care for much reduced cost to the patient, practice and health care system as a whole,” the authors concluded.