Biomedical subjects

Malin Frick-Engfeldt

Publications and source records attributed to Malin Frick-Engfeldt.

3 recordsLinked to original sources

PubMed2007

Variation in the amount of petrolatum preparation applied at patch testing.

The elicitation of a positive patch test reaction in a given individual depends upon the dose of the sensitizer applied, the patch test technique and the occlusion time. The dose is determined by the concentration and volume/amount of test preparation applied. If the same amount/volume of a test preparation is applied all the time with the same test technique (same area of skin) and occlusion time, it is appropriate to use concentration as a dose parameter. Most contact sensitizers are incorporated in petrolatum (pet.). With pet. as vehicle, it is impossible to repeatedly apply an exact volume/amount. This study was performed to investigate the inter- and intra-individual variation of pet. preparation applied at patch testing by 3 technicians. Weighing demonstrated that the 3 technicians had about the same precision in their pet. application. The investigation demonstrates that there is both an inter-individual (statistically significant) and intra-individual variation in the amounts of pet. applied at patch testing for the 3 technicians. Presently, there is no recommendation on what amount of pet. preparation to apply, which merits a decision to be taken based on thorough investigations on the appropriate volumes of pet. preparation to be applied in various patch test systems.

Dermatitis, Contact↗

PubMed2007

Is it possible to improve the patch-test diagnostics for isocyanates? A stability study of petrolatum preparations of diphenylmethane-4,4'-diisocyanate and polymeric diphenylmethane diisocyanate.

We have previously shown that the concentration of diphenylmethane-4,4'-diisocyanate (4,4'-MDI) in commercial test preparations was so low that patch testing with the same was not reliable. The stability of 4,4'-MDI in petrolatum (pet.) was compared with pet. preparations of polymeric diphenylmethane diisocyanate (PMDI), which consists of a complex mixture of monomeric isomers and oligomers of MDI. Preparations of 4,4'-MDI and PMDI were stored under 3 different conditions, i.e. at room temperature, refrigerated and frozen. They were analysed continuously during 1 year with regard to the content of 4,4'-MDI, 3-ring oligomers and 4-ring oligomers using liquid chromatography-mass spectrometry. PMDI preparations kept frozen were stable for a year. All other preparations failed to fulfil the requirements of stability, i.e. +/-20% of the initial concentration. Storage in a freezer prolonged the lifetime for 4,4'-MDI. The decrease in concentration for preparations kept at room temperature and refrigerated was less rapid in PMDI preparations than in 4,4'-MDI preparations. PMDI preparations are better suited for patch testing patients exposed to MDI because they are more stable and homogeneous than 4,4'-MDI preparations. They better reflect possible allergens that workers are exposed to because products used in industry contain both monomers and oligomers.

Chromatography, Liquid↗

PubMed2005

Chemical analysis of 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate and isophorone diisocyanate in petrolatum patch-test preparations.

BACKGROUND: Isocyanates with the general formula R-(N=C=O) are theoretically contact sensitizers. However, allergic contact dermatitis (ACD) from isocyanates is seldom reported. In previous reports, patients reacted to their isocyanate-based work materials but not to commercial patch-test preparations of isocyanates. Therefore, we suspected that the low frequency of reported ACD from isocyanates was partly due to inadequate commercial preparations. A past study also showed the concentrations of diphenylmethane-4,4'-diisocyanate (4,4'-MDI) in petrolatum preparations to be much lower than declared. OBJECTIVE: In this study, 2,4-toluene diisocyanate (2,4-TDI), 1,6-hexamethylene diisocyanate (1,6-HDI), and isophorone diisocyanate (IPDI) were investigated in a similar fashion. METHODS: In preparations from 12 dermatology departments and two suppliers of patch-test allergens, we determined the isocyanate content as the isocyanate-dibutylamine derivative, using liquid chromatography and mass spectrometry. The preparations were considered stable if the ratio between the stated and found concentrations was within the range of 0.8 to 1.2. RESULTS: Although 28 of 36 investigated preparations had ratios outside of the stable range, they were in its vicinity, which indicates that preparations of 2,4-TDI, 1,6-HDI, and IPDI are more stable than are preparations of 4,4'-MDI where previously reported results showed ratios far outside of stable range. CONCLUSION: As opposed to preparations of 4,4'-MDI, preparations of 2,4-TDI, 1,6-HDI, and IPDI can be considered to be stable.

Cyanates↗