The ready-to-use T.R.U.E. TEST® patch test system contains 29 allergens and allergen mixes that are responsible for up to 80% of allergic contact dermatitis. Reference 3.
The allergens in T.R.U.E. TEST® require no preparation. The standardized allergens and allergen mixes are already incorporated into hypoallergenic, dehydrated, hydrophilic gels attached to a waterproof backing. Upon application of T.R.U.E. TEST®, a patients´s perspiration and transepidermal water loss quickly re-hydrates the dried gel layer, thereby releasing the allergens onto the skin. References 8 and 10. After 48 hours, T.R.U.E. TEST® is removed. Reactions are then interpreted at 72 to 96 hours after test application.
The homogeneous distribution of allergens assists to minimize the potential for false-positive and irritant reactions. To help ensure accurate testing and interpretation, the placement of allergens is standardized with T.R.U.E. TEST®. Allergen stability has been confirmed by in vitro studies, and an optimized allergen dose level has been determined by in vivo dose-response studies. Reference 12.
The allergen doses in T.R.U.E. TEST® are sufficient to elicit allergic reactions in weakly sensitized patients, yet low enough to minimize the risk of iatrogenic sensitization. Because the allergens are dehydrated, there is minimal risk of allergen overflow and cross-contamination. With no need to mix and formulate allergens, T.R.U.E. TEST® minimizes preparation time. Reference 13.
Unit packaging also contributes to reliability and quick preparation time. Each test panel is wrapped in an airtight foil outer cover for protection from light and moisture. Each allergen patch is attached to an impermeable, flexible plastic backing that promotes optimal contact between skin and allergen, thereby maximizing allergen penetration. The occlusive backing and allergen patches are held firmly in place by a single piece of nonwoven, hypoallergenic, semi-occlusive surgical tape. The porous nature of the tape should minimize the risk of miliaria and irritation.
The design features of T.R.U.E. TEST® help ensure that its prepackaged, standardized allergens perform consistently and reproducibly, with minimal preparation.
World-wide more than 40 clinical studies involving over 5,500 patients have been conducted to evaluate the consistency, reproducibility, optimal dose, performance, safety, efficacy and clinical relevance of T.R.U.E. TEST® patch test system. T.R.U.E. TEST® has been shown consistently to provide a safe, effective, clinically relevant method of diagnosing Allergy Contact Dermatitis (ACD). Reference 12.
Consistency and reproducibility
T.R.U.E. TEST® has been tested clinically for consistency and reproducibility in several studies. Reference 12. In each study, three separate production lots of allergens were evaluated for uniform reactivity. All patients had previously confirmed allergy to the test allergens.
In one study of 39 patients, three production batches of nickel sulfate, ethylenediamine dihydrochloride and epoxy resin produced similar positive results in 90% to 100% of reactions. Reference 12. There were two discordant reactions in patients with known nickel sensitivity. One patient sensitized to nickel sulfate showed two strong (++) reactions to Batches No. 1 and 2 and a negative (-) reaction to Batch No. 3. The second evaluator made the same interpretation. A second nickel-sensitive patient had a weak (+) reaction to Batches No. 2 and 3 and a negative (-) reaction to Batch No. 1. In evaluating this patient, a second evaluator scored strong (++) reactions for Batches No. 2 and 3 and a weak (+) reaction for Batch No. 1. Evaluations were performed at 72, 96, or 120 hours. Reference 12.
A second study was a randomized, double-blind, placebo-controlled investigation conducted with 47 patients, 42 of whom had responses. Reference 12. Balsam of Peru, black rubber mix, Cl+ Me- isothiazolinone, and thiuram mix produced consistent positive reactions in 93% of cases (39/42), with no discordant reactions observed. The reactions were interpreted by two independent observers. The study found complete correspondence between the two evaluations for responses to all allergens evaluated. Reference 12.
In a third study, also a randomized, double-blind, placebo-controlled trial, three lots of p-phenylenediamine generated consistent test reactions in 90% of patients (9/10). Reference 12.There were no discordant reactions in this study.
Taken together, the results of these studies demonstrated good reproducibility from different production lots of allergens contained in TRUE TEST (See Table 1). Reference 12 and 14.