Comparative study of the density of particles in suspensions for patch testing

S3 guidelines: Epicutaneous patch testing with contact allergens and drugs - Short version, Part 1

Epicutaneous patch testing is the diagnostic standard for the detection of allergic contact dermatitis. The present guidelines are aimed at residents and board-certified physicians in the fields of dermatology and allergology as well as other medical specialties involved in establishing the indication for patch testing and its execution in patients with contact dermatitis and other forms of delayed-type hypersensitivity. The target audience also includes other health care providers and insurance funds. Based on a systematic literature search and a formal consensus process (S3), the guidelines were developed by dermatologists in collaboration with pediatricians, occupational medicine physicians, nursing staff as well as patient representatives. The systematic methodological approach and appraisal of evidence upon which the recommendations are based are outlined in a separate method report that also contains evidence tables. The guidelines address general aspects of patch testing as well as medicolegal issues. The recommendations given relate to topics such as the indication for patch testing, informed patient consent, as well as the choice of test substances, test chambers and test site, duration of exposure, reading times and interpretation of test reactions. Furthermore, recommendations are provided with respect to endogenous and exogenous factors, specific patient groups (children, pregnant women, immunosuppressed individuals) as well as possible risks and adverse events associated with patch testing using contact allergens. Note: This publication is part 1 of the short version of the S3 guidelines for "Epicutaneous patch testing using contact allergens and drugs" (registry no. 013 - 018; date: March 20, 2019; valid until December 31, 2021). Part 2 of the short version will be published in the next issue. The long version of these guidelines can be accessed at www.awmf.org. The method report is available as online publication (https://www.awmf.org/leitlinien/detail/ll/013-018.html) and contains the evidence tables in its appendix.

Reproducibility of patch test results: a concurrent right-versus-left study using TRUE Testtm

Wide variations in the reproducibility rate of positive patch test responses have been reported. We hypothesized that a major source of non-reproducibility resides in the methodological pitfalls of routine patch testing. Simultaneous duplicate patch testing on opposite sides of the upper back was performed on 500 consecutive patients, using the TRUE Test system consisting of 2 panels, each one containing 12 standard allergens. A rigorous methodological design was applied and relevance was assessed for all discordant patch test reactions. A total of 435 positive patch test reactions were observed either on one or both sides in 289 patients (58.8%). Of these, 22 (5%) were discordant, i.e. interpreted as positive allergic on one side whilst negative or doubtful on the opposite side. The allergens responsible for discordant reactions were nickel sulfate (4 patients), cobalt chloride (3), lanolin alcohol (3), fragrance mix (2), carba mix (2), thiuram mix (2), colophonium (1), potassium dichromate (1), p-phenylenediamine (1), formaldehyde (1), balsam of Peru (Myroxylon pereirae resin) (1) and thimerosal (1). Of the 19 (4%) patients with discordant patch test reactions, the allergen was deemed to be of definite present or past relevance in 9 patients (1.8% of the total and 3.1% of all patients with positive patch test reactions) and of possible relevance in a further 2 patients. These data suggest that patch testing is a reasonably reproducible procedure as long as methodological error is minimized.

Comparison of colophony patch test preparations

The patch test reactivity to different petrolatum preparations and concentrations of colophony (gum rosin) was compared. A serial dilution test with gum rosin 20%-0.001% gave a clear dose-response relationship with a maximum response to 10% and 20%. Patch testing with 60% in the routine test did not reveal any further cases compared to simultaneous testing with 20%. Irritancy to the 60% concentration was seen in some cases. A good correlation in reactivity was found between commercially-supplied test preparations for routine testing and homogeneous preparations made up in our laboratory. Our results imply that a concentration of 10% is well worth considering for routine testing.

False-positive, follicular and irritant patch test reactions to metal salts

853 hard metal workers were patch tested with nickel sulphate 5%, potassium dichromate 0.5% and cobalt chloride 1%, each in petrolatum. Non-allergic reactions appeared in 6.5% of the nickel tests, 13% of the chromium tests and 18.3% of the cobalt tests. Most of the individuals with positive, poral or pustular reactions were retested with serial dilutions of metal salts in pet. and in water. The accuracy of a positive initial nickel reaction was 83%, a chromium reaction 40% and a cobalt reaction 62%. The nonallergic reactions were partly reproducible and correlated with both the type of patch test material and with individual factors. Weak and moderately strong positive patch test reactions to metal salts may be irritant and should be checked with serial dilution tests or at least be retested. A reduction of the cobalt chloride concentration from 1% to 0.5% in the standard test material is discussed.

The thin layer rapid use epicutaneous test (TRUE-test), a new patch test method with high accuracy

The thin layer rapid use epicutaneous test (TRUE-test) is a new patch test, in which the allergens are incorporated in a thin, flexible solid vehicle on a water impermeable backing. The vehicle shows good stability for allergens, which are crystallized, micronized or emulsified into a gel. The TRUE-test produces an exact dosage, even surface spread and high bioavailability for the allergens. This solves the problems of low bioavailability, uncertain dosage and uneven surface distribution which are commonly seen when petrolatum is used as the vehicle.

Patch test allergens in petrolatum: a reappraisal

Patch test materials in petrolatum, from 3 different manufacturers and 14 different types were evaluated by gross and microscopic examination. The allergens were noted to be suspended as particles or droplets in the vehicle. Obvious variations in both size and structure of the included allergen were found with the same chemicals but of different manufacture. Several materials do not meet the pharmaceutical standards which should be requested regarding stability, particle size and packing. A more detailed declaration is proposed.

24 and 48 h allergen exposure in patch testing. Comparative study with 11 common contact allergens and NiCl2

Patch test reactions to 11 common contact allergens were studied after 24 h and 48 h occlusion with Finn Chambers in 390 patients. Concordant allergic results were found in 96 cases (74%). In 22 patients (17%), the reaction was positive only after 48 h and in 11 cases (8.5%) only after 24 h exposure. Most of the discordant reactions were to nickel, cobalt, neomycin, formaldehyde and perfume mix. Irritant reactions were found in 55 cases, the majority occurring after 48 h occlusion. Nickel chloride tested in parallel with 48 h exposure lead to more positive allergic and toxic reactions than nickel sulphate.