J Welch

Specific IgE to isocyanates: A useful diagnostic role in occupational asthma

BACKGROUND Isocyanates are the most frequent cause of occupational asthma in industrialized countries. OBJECTIVE We sought to investigate the utility of specific IgE measurement in the diagnosis of isocyanate-induced asthma. METHODS Fifty-eight of 101 patients referred for investigation were diagnosed as having isocyanate-induced occupational asthma by means of history, serial peak flow records, and bronchial provocation tests. Specific IgE antibodies to toluene diisocyanate:human serum albumin (HSA), diphenylmethane diisocyanate:HSA, and hexamethylene diisocyanate: HSA were measured in all patients by Phadebas RAST. RESULTS Twenty patients had a RAST ratio of 2 or greater to at least one isocyanate. Thirteen (28%) of the 46 patients with a positive provocation test response had a RAST ratio of 2 or greater, and nine (20%) had a RAST ratio of 3 or greater. Raising the RAST cut-off from 2 or greater to 3 or greater reduced its sensitivity but increased the specificity of the test to 100%. RAST measurement was most likely to be positive within 30 days of exposure. Serial measurements suggested that the half-life of the IgE antibodies was approximately 6 months. Evidence of cross-reactivity between isocyanate RAST responses was found in eight subjects. CONCLUSION Specific IgE to isocyanates is a more specific than sensitive index of occupational asthma. With a RAST score of 3 or greater, it is wholly specific and therefore diagnostic of isocyanate-induced asthma. The sensitivity of specific IgE measurement is highest when blood is taken less than 30 days from last exposure, which is consistent with the observed half-life.

Occupational asthma caused by cellulase and lipase in the detergent industry

Three employees from two different detergent companies were investigated for occupational asthma, using skin prick tests, serum specific IgE, and specific bronchial challenge. Two were challenged with lipase and one with cellulase. All three cases had immunological evidence of sensitisation to the detergent enzymes with which they worked. Bronchial challenge in each provoked a reproducible dual asthmatic response, which reproduced their work related symptoms. These are the first reported cases of occupational asthma attributable to cellulase and lipase in the detergent industry. Four of the most common enzymes used in this industry have now been reported to cause occupational asthma; continued vigilance and caution are needed when working with these or other enzymes.

Prevalence of sensitization to 'improver' enzymes in UK supermarket bakers.

Supermarket bakers are exposed not only to flour and alpha‐amylase but also to other ‘improver’ enzymes, the nature of which is usually shrouded by commercial sensitivity. We aimed to determine the prevalence of sensitization to ‘improver’ enzymes in UK supermarket bakers.

Occupational allergy to fruit flies (Drosophila melanogaster) in laboratory workers

Objectives Drosophila melanogaster (the ‘fruit fly’) is commonly used in genetic research, but there is only one report of IgE-associated allergy in exposed workers. 4 newly identified cases prompted us to examine the extent of this problem in a university laboratory. Our aim in this study is to determine the prevalence and determinants of sensitisation to fruit flies in a population of exposed workers. Methods In a cross-sectional study, we surveyed 286 employees working in a department carrying out research involving D. melanogaster. Sensitisation was assessed by specific IgE measurement in serum and examined in relation to symptoms and to estimated exposure to fruit flies. Results The overall prevalence of specific sensitisation was 6% with a clear relationship to increasing frequency/intensity of exposure (p trend<0.001). Work-related eye/nose, chest or skin symptoms were reported by substantial proportions of participants but for most of these there was no evidence of specific sensitisation to fruit fly. The overall prevalence of any work-related symptoms and sensitisation was 2.4%, rising to 7.1% in those working in high exposure groups. Conclusions We were able to demonstrate, for the first time, a clear exposure–response relationship between fruit fly exposure and specific sensitisation. Facilities housing fruit flies should carefully consider methods to reduce exposure levels in the workplace.

Allergenicity of grass and oil seed rape pollen

In a recent Viewpoint, Denis Murphy discussed the allergenicity of oilseed rape1xIs rapeseed really an allergenic plant? Popular myths versus scientific realities. Murphy, D. Immunol. Today. 1999; 20: 511–514Abstract | Full Text | Full Text PDF | PubMed | Scopus (7)See all References1. In his interesting article, Murphy suggests that patients allergic to oilseed rape pollen are a subset of the more extensive pool of patients with grass pollen allergies who also recognize crossreacting epitopes in oilseed rape pollen.We have recently completed a study investigating whether oilseed rape sensitization is due to crossreactivity with grass pollen2xSee all References2. The allergens of grass and oilseed rape pollen are of similar molecular weights: 14, 21 and 33 kDa for oilseed rape; and 14, 17, 32 and 39 kDa for grass pollens. Despite allergens of similar molecular weights being present in both pollen types, competitive RAST and inhibition immunoblot studies confirmed that the allergens of grass and oilseed rape pollen were immunologically distinct. Grass pollen was unable to inhibit the binding of IgE to oilseed rape and, similarly, oilseed rape did not inhibit the binding of IgE to grass pollen, although there was complete self-inhibition.Our findings would not support the speculation that sensitization to oilseed rape pollen was predominantly due to crossreactivity with grass pollen. This finding is particularly important for those individuals occupationally exposed to oilseed rape pollen who may also be sensitized to grass pollen.

S103 Occupational allergy to fruit flies (drosophila melanogaster) in laboratory workers

Introduction and Objectives Drosophila melanogaster (the ‘fruit fly’) is commonly used in genetic research, but there is only one earlier report of immunoglobulin E-associated allergy in exposed workers. Four newly identified cases prompted us to examine the extent of this problem in a university laboratory. Our aim was to determine the prevalence and determinants of sensitisation to fruit flies in a population of exposed workers. Methods In a cross sectional study we surveyed two hundred and eighty six employees working in a department carrying out research involving D. melanogaster. Sensitisation was assessed by specific IgE measurement in serum using radioallergosorbent assay (RAST) and examined in relation to work-related symptoms and to estimated exposure to fruit flies. Results The overall prevalence of specific sensitisation was 6% with a clear relationship to increasing frequency/intensity of exposure (p trend <0.001). Work-related eye/nose, chest or skin symptoms were reported by substantial proportions of participants but for most of these there was no evidence of specific sensitisation to fruit fly. The overall prevalence of any work related symptoms and sensitisation was 2.4%, rising to 7.1% in those working in high exposure groups. Conclusions We were able to demonstrate, for the first time, a clear exposure-response relationship between fruit fly exposure and specific sensitisation. Facilities housing fruit flies should carefully consider methods to reduce exposure levels in the workplace.

P53 Determination of specific IgE antibodies to mouse proteins in laboratory animal workers

Introduction Laboratory animal workers are at increased risk of developing specific IgE antibodies to laboratory animal proteins. The major allergen for mouse is Mus m 1 which is predominantly found in the urine. Specific IgE to mouse is determined using either a commercial skin prick test solution of mouse epithelium or ImmunoCAP for either mouse urine or epithelium. Specific IgE to Mus m 1 is used for routine diagnostic testing. The aim of this study was to compare sensitisation using both ImmunoCAP and skin prick test as well as compare mouse urine and epithelium as allergens. At present there is no gold standard for sensitisation to mouse allergens. Methods Laboratory workers exposed to mice were recruited to the SPIRAL (Safe Practice in Reduction of Allergy in Laboratories) study. Sensitisation was determined by the presence of specific IgE to Mus m 1 and mouse epithelium using ImmunoCAP (Phadia) (positive result ≥0.35 kU/l) and by skin prick test to mouse epithelium (positive result is a saline adjusted mean wheal diameter of ≥3 mm). Results Of the participants (321), 11 (3%) were positive by skin prick test, 34(11%) with specific IgE to Mus m 1 and 35 (11%) with a positive specific IgE to mouse epithelium. There were 25/321(8%) participants with a discordant results between SPT and specific IgE to Mus m 1 (Table 1). There were 14 participants with a discordant result between specific IgE to Mus m 1 and mouse epithelium (Table 1).Abstract P53 Table 1 Specific IgE to Mus m 1 and mouse epithelium in laboratory animal workers Mus m 1 specific IgE positive Mus m 1 specific IgE negative Total SPT positive 10 1 11 SPT negative 24 286 310 Total 34 289 321 Mouse epithelium specific IgE positive 26 9 35 Mouse epithelium specific IgE negative 5 286 291 Total 31 295 326 Discussion Laboratory animal workers may have specific IgE antibodies to either Mus m 1 or mouse epithelium. Diagnostic tests for mouse sensitisation may require testing to both Mus m 1 and mouse epithelium to ensure we do not miss any sensitised cases. Skin prick tests appear higher rates of false negative than anticipated and are therefore less reliable in clinical practice if used alone.