Abstract

Background
Colophony (rosin) is a natural product obtained from coniferous trees. It is used in a diverse range of products such as adhesives, ink, paints and soldering fluxes. Some workers exposed to colophony during soldering can develop occupational asthma; at present, no specific IgE test is available to assess sensitization to colophony.

Methods
Serum samples were obtained from exposed symptomatic individuals (n=7), some with a likely diagnosis of occupational asthma, exposed asymptomatic individuals (n=10) and unexposed individuals (n=11). Serum was tested for specific IgE antibodies against a protein extract produced following in vitro challenge of mono-mac-6 cells with colophony extract.

Results
Serum from exposed symptomatic individuals showed increased binding of specific IgE antibodies to a range of colophony–cell protein conjugates [29% (2/7) of samples tested when cut-off >0.1 or 86% (6/7) of samples tested when cut-off >0%] compared with both the exposed asymptomatic [0% when cut-off >0.1, or 20% when cut-off >0% (2/10)] and the non-exposed control populations [0% when cut-off >0.1, or 27% when cut-off >0% (3/11)].

Conclusions
This novel approach for the production of conjugates to assess sensitization to colophony was able to detect specific IgE in colophony-exposed workers with a likely diagnosis of occupational asthma.

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