How to optimize patch testing with diphenylmethane diisocyanate.
We have previously shown that patch test preparations of polymeric diphenylmethane diisocyanate (PMDI) are more stable than preparations of diphenylmethane-4,4'-diisocyanate (4,4'-MDI). This study was conducted to (i) investigate whether PMDIs yield as many positive reactions as 4,4'-MDI, (ii) study concurrent reactions to 4,4'-MDI and 4,4'-diaminodiphenylmethane (4,4'-MDA), and (iii) follow the course of positive reactions during 4 weeks. It was shown that PMDIs detect as many positive reactions as 4,4'-MDI. Thus, they are better patch test agents being more stable than preparations of 4,4'-MDI. We recommend that PMDIs with a monomer content of at least 35% is used in 2.0% petrolatum (pet.) (i.e. monomer patch test concentration approximately 0.7%). It was shown that reactions to 4,4'-MDI and PMDIs appear late and we recommend readings on both day (D) 3/4 and D7. 4,4'-MDA was shown to be a good marker for 4,4'-MDI and patch testing with 4,4'-MDA in 0.25% pet. can be used instead of PMDI. Concomitant reactions to 4,4'-MDI and 4,4'-MDA are probably not caused by conversion of 4,4'-MDI into 4,4'-MDA by reaction with water. Another explanation is a path of reactions leading to ureas and MDI conjugates with skin constituents, which are hydrolysed into 4,4'-MDA. This complex process depends upon several factors and might explain why positive MDI reactions appear after D7.
Department of Occupational and Environmental Dermatology, Malmö University Hospital, Lund University, S-205 02 Malmö, Sweden. malin.frick@med.lu.se
Malin
M
Frick-Engfeldt
Marléne
M
Isaksson
Erik
E
Zimerson
Magnus
M
Bruze
D000293:Adolescent; D000328:Adult; D000814:Aniline Compounds / Q000009:adverse effects* / Q000737:chemistry; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis* / Q000209:etiology; D004355:Drug Stability; D005260:Female; D006801:Humans; D017953:Isocyanates / Q000009:adverse effects* / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000379:methods*; D011140:Polyurethanes / Q000009:adverse effects* / Q000737:chemistry; D013997:Time Factors; D001559:Benzhydryl Compounds
D000814:Aniline Compounds; D017953:Isocyanates; D011140:Polyurethanes; C087867:polymeric 4,4'-diphenylmethane diisocyanate; C005969:4,4'-diphenylmethane diisocyanate; D001559:Benzhydryl Compounds; C009505:4,4'-diaminodiphenylmethane