Pilot evaluation of a convenient and cost-effective method of patch testing.
OBJECTIVE
The primary objective of this double-blind randomized, pilot study was to evaluate whether previously prepared stored patches may be as effective as freshly prepared patches are for detecting contact allergy.


METHODS
Two sets of 62 nonaqueous allergens were applied to participants' upper backs. One set was freshly prepared, and the second set was previously prepared and stored for an average of 6 weeks. Right or left back location for each set was randomly assigned. The primary outcome assessment compared the proportions of fresh and strong reactions in pairs with complete discordance (negative on one side and 1+, 2+, or 3+ on the other side).


RESULTS
In 71 patients enrolled, there were 169 positive reactions. Concordance (any combination of a 1+, 2+, or 3+ reaction on both sides) was found in 63% of pairs (95% CI: 55.4, 70.0). Of the 25 pairs with complete discordance, there was no statistically significant difference between the rate of positive reactions for fresh and stored patches.


CONCLUSIONS
Pilot evidence suggests that stored patches may be effective in detecting the majority of allergic contact reactions. Larger studies are needed to evaluate antigen-specific effects as well as effects of varying lengths of antigen storage.
Warshaw
Erin
E
Center for Chronic Disease Outcomes Research, Minneapolis VA Medical Center and the Department of Dermatology, University of Minnesota, Minneapolis, MN, USA.
Liu
An
A
Jerstad
Kelly
K
Lee
Gina
G
Larson
Kathleen
K
Farrell
April
A
Bailey
Jacqueline
J
Nelson
Dave
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000485:Allergens / Q000737:chemistry; D003362:Cost-Benefit Analysis; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis*; D004311:Double-Blind Method; D004356:Drug Storage; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000592:standards*; D010865:Pilot Projects; D011237:Predictive Value of Tests
D000485:Allergens