SKIN TEST PANEL SIZE
A recent question was raised about the size of allergy skin test panels and what is medically appropriate. The concept of medical necessity is somewhat subjective when it comes to allergy testing – I could also use the phrase medically reasonable. A lot depends on the characteristics of the patients coming into the clinic…and this can be highly variable.
The current practice guidelines on Allergy Diagnostic Testing do not currently advocate for any specific number of allergens for skin test panels. It does encourage avoiding panels that test for excessive numbers of allergens or allergens that may not be clinically meaningful.
When considering how many allergens is “too many” or “too few", a clinic must strike a balance between the scientific & clinical rationale for allergen coverage, patient comfort and affordability, and of course, profitability of performing the test procedure.
There is no absolute when it comes to the ideal number of allergens to be tested for inhalant allergy. A variety of factors can affect the number and diversity of allergens selected for testing, including location of the clinic, profile of patients, the types of allergic conditions commonly reported, as well as the layout of testing tray.
During my tenure as Associate Scientific Director with an allergenic extract manufacturer (ALK), I personally evaluated hundreds of allergy skin test panels from Allergy Specialist offices throughout North America. I found that there was a large range in the quantity of allergens selected for routine skin testing for inhalant allergy, and here is my general consensus on the size of panels and their coverage for inhalant allergy:
- Basic or Core Panel: 24 to 36 allergens; tests just the basic allergen classes but risks missing occupational allergens, unique regional allergens, and possibly entire allergen classes or botanical families.
- Average Panel: 40 to 60 allergens; common for standard regional panels, but risks missing allergens unique to other areas of the country and does not provide any areas of redundancy for critical allergen groups (to help minimize false negative test results).
- Comprehensive Panel: 64 to 80 allergens; provides the highest degree of inhalant allergen coverage and includes a reasonable number of cross-reactive allergens to ensure important allergen families are properly covered and interpreted correctly.
- Excessive Panel: 90-120+ allergens; this size panel will often include unnecessary allergens or allergenic extracts with dubious clinical utility. (e.g. Goldenrod, Kapok, Pyrethrum, Cotton Linters, obscure fungal allergens, and some obscure dander allergens)
Below are a few situations when a smaller or more regionalized panel would be clearly justified:
- Pediatric clinic – a smaller test panel has both clinical and practical advantages over a broader testing array when performing skin prick testing on kids.
- Small rural clinics – often have a high percentage of “local” patients so a more diverse set of allergens may not be necessary, or there is a high percentage of patients with a high out-of-pocket responsibility.
- Clinics new to allergy – may opt for a smaller panel to become familiar with the testing procedure and then determine if a more robust panel would be appropriate for their allergic patients.