Relevance of doubtful ("equivocal") late patch-test readings

Area of Science:

• Dermatology
• Allergology
• Clinical Immunology

Background:

• Doubtful late patch test readings are often dismissed as clinically irrelevant.
• This can lead to patients not being informed about or avoiding relevant allergens.
• This study investigates the clinical relevance of these doubtful reactions.

Purpose of the Study:

• To determine if doubtful late patch-test reactions (Day 7 reading) are clinically relevant.
• To compare patient-assessed relevance with the strength of patch test reactions at 168 hours.

Main Methods:

• A survey was sent to 407 subjects who underwent patch testing.
• Subjects reported dermatitis improvement and need to avoid allergens.
• Patient responses were correlated with Day 7 patch test reaction strengths from clinical charts.

Main Results:

• 63% of negative, 79% of doubtful (?+), 85% of +, 84% of ++, and 100% of +++ late readings were deemed relevant.
• Doubtful reactions were considered relevant by patients nearly as often as + reactions.

Conclusions:

• Allergens with doubtful late patch test reactions appear to be clinically relevant.
• These findings suggest that doubtful reactions should be disclosed to patients.
• Further validation of survey methods and addressing response bias are recommended.