Is p-tert-butylphenol-formaldehyde resin (PTBP-FR) in TRUE Test (R) (Mekos test) sensitizing the tested patients?

Background. In a population study using TRUE Test (R), we noted late reactions to p-tert-butylphenol-formaldehyde resin (PTBP-FR) in 0.5% of subjects tested. Objectives. In order to explore possible test sensitization, differences in the contents of sensitizers within PTBP-FR in test preparations for TRUE Test (R) and Finn Chambers (R) were analysed. Subjects allergic to PTBP-FR and subjects with late reactions to PTBP-FR were retested in order to explore whether these groups reacted to different PTBP-FR sensitizers. Pallents/materials/methods. Four individuals with late reactions and 5 subjects with established allergy to PTBP-FR were retested with defined PTBP-FR sensitizers. PTBP-FR constituents in patches from TRUE Test (R) were analysed with high-performance liquid chromatography. Previously analysed samples of PTBP-FR constituents served as a reference. Results. The pattern of reaction to PTBP-FR sensitizers was similar in both groups. Subjects with suspected sensitization had somewhat stronger reactions than controls. The concentrations of monomers, dimers and trimers were generally higher in the TRUE Test (R) resin than in reference substances. Conclusions. Retesting did not add information regarding causes of possible sensitization. Analysis showed that the resin used in TRUE Test (R) has a lower degree of polymerization or condensation, which may enhance its sensitizing properties. A follow-up of late reactions to PTBP-FR in TRUE Test (R) should be carried out.