Inter-rater variability in patch test readings and final interpretation using store-forward teledermatology.

Background: Data regarding teledermatology for patch testing are limited.

Objectives: Compare patch test readings and final interpretation by two in-person dermatologists (IPDs) with eight teledermatologists (TDs).

Methods: Patch tested patients had photographs taken of 70 screening series of allergens at 48 hours and second readings. Eight TDs reviewed photos and graded reactions (negative, irritant, doubtful, +, ++, +++) at 48 hours and second readings; in addition, they coded a final interpretation (allergic, indeterminant, irritant, negative) for each reaction. TDs rated overall image quality and confidence level for each patient and patch test reaction, respectively. Percentage of TD-IPD agreement based on clinical significance (success, indeterminate, and failure) was calculated. Primary outcome was agreement at the second reading.

Results: Data were available for 99, 101, and 66 participants at 48 hours, second reading, and final interpretation, respectively. Pooled failure (+/++/+++ vs negative) at second reading was 13.6% (range 7.9%-20.4%). Pooled failure at 48 hours and final interpretation was 5.4% (range 2.9%-6.8%) and 24.6% (range 10.2%-36.8%), respectively. Confidence in readings was statistically correlated with quality of images and disagreement.

Conclusion: For patch testing, teledermatology has significant limitations including clinically significant pooled failure percentages of 13.6% for second readings and 24.6% for final interpretation.