Investigation of the homogeneity of methacrylate allergens in commercially available patch test preparations.

BACKGROUND: The homogeneity of methacrylates in commercial patch test preparations has not yet been investigated. Inhomogeneous patch test preparations may give rise to false-negative or false-positive patch test results in patients suspected of having methacrylate allergy.

OBJECTIVES: To investigate the homogeneity of methacrylates in commercial patch test preparations.

METHODS: Fresh commercial patch test preparations of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (2-HEMA) from three test material suppliers in Europe were analysed quantitatively by means of normal-phase high-performance liquid chromatography.

RESULTS: The initial concentration of MMA in all six patch test preparations was lower than stated on the label, whereas four of six patch test preparations of 2-HEMA were in accordance with the stated concentrations. The concentration of MMA increased markedly from the top segment close to the tip of the syringe to the bottom segment adjacent to the piston in four syringes (3-6). In contrast, syringes with 2-HEMA maintained a constant concentration throughout the test preparation, apart from two syringes (11 and 12).

CONCLUSION: Variations in concentration and heterogeneous distribution of MMA and 2-HEMA in patch test preparations may be an additional cause of variation in patch test results, besides other technical details and reading.