An investigation of operating theatre staff exposed to humidifier fever antigens

Discriminant analysis of symptom pattern and serum antibody titres in humidifier related disease

BACKGROUND

The heterogeneous patterns of symptoms among factory workers exposed to aerosols from contaminated air humidifiers were analysed to assess the association between specific symptoms and the serum IgG antibody response to the humidifier water contaminants, and to test the ability of specific symptoms to predict this antibody response.

METHODS

Symptoms from 88 factory workers were surveyed by a doctor administered questionnaire and compared with their serum IgG antibody titres to humidifier water contaminants quantified by enzyme immunoassay.

RESULTS

The strength of association between individual symptoms and antibody showed that fever, shivering or chills, influenza-like symptoms, or headache were individually significantly associated with the presence and higher titres of antibody. This was also true for those subjects whose symptoms were most pronounced during the first day of the working week. Within each subject's full symptom profile there were significant associations between the description of chest tightness, breathlessness, and wheeze; between headache and influenza like symptoms; between fever and shivering or chills; and between intermittent onset and general tiredness. Discriminant analysis of the full symptom profiles showed that there was maximum information content in five independent parameters, namely, the descriptions of fever, headache, and chest tightness, the timing of their onset, and the readiness to describe miscellaneous symptoms in addition to those in the questionnaire. On the basis of these criteria 72% of subjects could be classified according to their antibody state. Cluster analysis with these five independent parameters described four symptom clusters: one associated with high median antibody levels, one with low, and two with zero median levels. These were, respectively: (1) fever with headache and chest tightness; (2) either no or few symptoms; (3) chest tightness and headache with intermittent onset; (4) headache and miscellaneous symptoms with intermittent onset.

CONCLUSIONS

The association between serum antibody titres and specific symptom patterns may identify different categories of disease which constitute the spectrum known as humidifier related disease, and strengthens the hypothesis that antibody may be involved in the pathogenesis of some components of the disease.

Radiographic changes in humidifier fever

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Lung function of workers exposed to antigens from a contaminated air-conditioning system

Following the manifestation of humidifier fever in a number of workers in a carpet yarn texturing plant, a comparative study was begun of a group of workers exposed to fungi from the air-conditioning system and a control group not so exposed. For both group of workers anamnestic data were collected, intracutaneous skin tests were performed, certain lung function parameters were determined, and the presence of antibodies to a number of antigens from the system was tested for. It was found that the group of exposed workers had a significantly higher rate of positive intracutaneous skin test than non-exposed workers. Additionally, their serology was more often positive. Both positive skin test and positive serology were more frequent in non-smokers than in smokers. A positive immediate skin reaction among exposed workers was found to correlate with an FEF25-75 reduction during the working week. A positive delayed skin reaction among exposed workers correlated with a lower FVC prior to the start of the working week than recorded for non-exposed workers. A positive serology in exposed workers did not correlate with a difference in lung function compared with non-exposed workers, nor was there a correlation with a change in lung function in the course of the working week. When humidifier fever is diagnosed, steps should be taken to reduce exposure. It would also appear desirable to keep exposed workers under medical observation and to monitor the subsequent development of their lung function.

Allergy in laboratory animal workers

179 people working with small laboratory animals were studied by questionnaire, lung-function tests, skin tests with common allergen extracts and extracts of the serum and urine of five animal species, and serology. 49 people had symptoms related to animal contact, most commonly rhinitis but also asthma and skin rashes. Skin reactivity to animal extracts was related to symptoms, particularly asthma, but many people with rhinitis only had negative skin tests. Positive skin tests without symptoms were rare. 3 people had additional late skin reactions. Atopic individuals were no more likely than non-atopics to have animal-related symptoms but were more likely to have asthma. Gel diffusion revealed no precipitating antibodies, and no specific IgG was detected with the ELISA technique. Lung-function measurements were normal. Sensitisation to laboratory animals may involve heavy antigen exposure, so that relatively unreactive individuals can be affected. Exclusion of atopic individuals from work with laboratory animals will not eliminate the problem.