OSCE — Wood lamp examination of intertrigo, hypopigmentation, and scalp scale

Brief (to candidate)

You have a hand-held Wood lamp and a patient with axillary discolouration, truncal hypopigmented scale, and a child contact with scalp scale. In 8 minutes, demonstrate and explain Wood-lamp examination and interpret likely patterns to the examiner.

Candidate instructions

1. State UVA / ~365 nm principle and dark-room setup.
2. Describe skin preparation (clean, dry, no makeup/lint).
3. Map coral-red → erythrasma, yellow-gold → versicolor, green hair → Microsporum.
4. Explain why negative scalp fluorescence does not exclude tinea capitis.
5. Name one false-positive source and one confirmatory test pathway.
6. Mention vitiligo blue-white mapping or urine porphyrin caveat if asked.

Examiner checklist (mark each domain / 10)

Model key actions

• Demonstrate dark-room technique verbally if physical darkening unavailable.
• Give colour table cleanly without over-calling melanoma diagnosis from lamp alone.

Common errors

• Claiming negative lamp excludes all tinea capitis.
• Skipping dark-room requirement.
• Treating every fluorescence as pathognomonic without KOH/culture.