Patch Testing — SCE Dermatology MCQ

Correct answer: B — Approximately 30 allergens (updated periodically by the European Society of Contact Dermatitis)

The correct answer is B, approximately 30 allergens, updated periodically by the European Society of Contact Dermatitis (ESCD). The European baseline series is not a fixed panel but a dynamic, evidence-based set of the commonest and most clinically relevant contact allergens (nickel, fragrance mix I and II, balsam of Peru, potassium dichromate, colophony, MI/MCI, paraphenylenediamine and corticosteroids among others), revised as epidemiological data on sensitisation prevalence changes. Its purpose is to screen efficiently for the allergens most likely to explain a patient's contact dermatitis before adding supplementary or bespoke series based on occupational or cosmetic exposure history. The number sits around 25 to 30 (varies slightly by year of revision), which is the discriminating fact tested here, distinguishing it from the much larger or smaller distractor numbers. Why the other options are wrong: A. 100: This vastly overstates the baseline series; panels of this size would only be reached by combining baseline testing with multiple extended or specialist series (occupational, cosmetic, rubber, metal series) in a complex case. C. 200: This figure reflects the total number of allergens available across all commercial and specialist patch test series worldwide, not the screening baseline panel used as first-line testing. E. 5: A panel this small would miss the great majority of relevant allergens and could not achieve the sensitivity required for a screening series; it resembles a rudimentary or incomplete test kit, not the ESCD standard. D. Only 3: This is far too limited to have any diagnostic screening value and does not correspond to any recognised standard patch test series. Key point: The European baseline series is a dynamic ESCD-curated panel of roughly 25 to 30 key contact allergens, periodically revised, designed to detect the majority of clinically relevant contact allergies before extended series are added.

Reference: British Dermatological Nursing Group, Patch Testing: A Best Practice Guide (2016), citing Wilkinson et al. 2012 and Goossens 2010 on the European baseline series; https://bdng.org.uk/wp-content/uploads/2017/02/FINAL130117.pdf