CDT Allergy Testing & Patch Testing 2

Question 1

According to the ICDRG grading system, what does a '++' reaction indicate?

Accepted Answer

Strong positive with erythema, infiltration, and vesicles

Answer

In the ICDRG scale, '++' (strong positive) indicates erythema, infiltration, papules, and vesicles at the patch test site.

Question 2

A '?' (doubtful/questionable) reaction in patch testing is characterized by:

Accepted Answer

Faint macular erythema without infiltration

Answer

A doubtful or questionable reaction shows only faint macular erythema without any infiltration and is not considered a definitive positive result.

Question 3

What key feature differentiates an irritant reaction from a true allergic reaction on patch testing over time?

Accepted Answer

Irritant reactions fade by the final reading while allergic reactions persist or worsen

Answer

Irritant reactions typically diminish in intensity between the 48-hour and 72–96 hour readings, whereas true allergic reactions persist or increase.

Question 4

When is the final reading of a patch test typically performed?

Accepted Answer

72–96 hours after application

Answer

The final reading is performed at 72–96 hours to allow differentiation between true allergic and irritant reactions that may look similar at 48 hours.

Question 5

What is 'excited skin syndrome' (angry back) in patch testing?

Accepted Answer

False-positive reactions caused by strongly positive nearby test sites

Answer

Angry back syndrome occurs when a strong nearby positive reaction on the test panel influences adjacent sites, producing false-positive results in neighboring allergens.

(CDT) Certified Dermatology Tech Practice Test

(CDT) Certified Dermatology Tech Practice Test

CDT Allergy Testing & Patch Testing 2