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The case for patch test readings beyond day 2. Notes from the lost and found department
R L Rietschel1, R M Adams, H I Maibach
1Department of Dermatology, Ochsner Clinic, New Orleans, LA 70121.
Journal of the American Academy of Dermatology
|January 1, 1988
Summary
Delayed patch testing readings are crucial for accurate allergy diagnosis. Follow-up assessments identify false positives and detect additional positive reactions, improving clinical relevance.
Area of Science:
- Dermatology
- Allergology
- Immunology
Background:
- Patch testing is a standard diagnostic tool for allergic contact dermatitis.
- Accurate interpretation of patch test results is essential for effective patient management.
- Standard reading times may miss delayed hypersensitivity reactions.
Purpose of the Study:
- To evaluate the clinical utility of delayed patch test readings.
- To determine the frequency of delayed positive and negative reactions.
- To assess the impact of delayed readings on diagnostic accuracy.
Main Methods:
- Patch tests were applied to patients with suspected allergic contact dermatitis.
- Initial readings were performed at 48 hours.
- Additional readings were conducted between days 3 and 7.
Main Results:
- Delayed readings (days 3-7) identified an additional 34% of positive reactions.
- False-positive reactions occurred in up to 22% of cases at the initial 48-hour reading.
- Persistent reactions beyond 48 hours and reactions changing between readings (lost or found) require clinical correlation.
Conclusions:
- Delayed patch test readings significantly enhance the detection of allergic contact dermatitis.
- Second readings are valuable for distinguishing true positives from false positives.
- Incorporating delayed readings improves the diagnostic yield and clinical relevance of patch testing.