Age-dependent interaction between atopy and eosinophils in asthma cases: results from NHANES 2005-2006.

BACKGROUND: Atopy is an established risk factor for asthma, and an elevated eosinophil level is a hallmark of atopic and non-atopic asthma. Whether atopy and eosinophils act independently or interact to influence asthma has clinical and public health implications. OBJECTIVE: To investigate the relationship between atopy and eosinophils in asthma. METHODS: Data on current asthma, atopy (IgE positive to ≥ 1 allergen), and blood eosinophil percent (dichotomized at the median) were obtained for persons aged ≥ 6 years from the National Health and Nutrition Examination Survey 2005-2006. Interaction on an additive scale was evaluated by estimating the prevalences of asthma for combinations of atopy (yes or no) and eosinophil percent (high or low) and calculating the excess prevalence due to interaction. RESULTS: For all ages combined, the adjusted prevalences of asthma were 4.6%, 7.6%, 6.9% and 17.2% for persons with neither factor, atopy alone, a high eosinophil percent alone and both factors respectively. The excess prevalence of asthma due to interaction was 7.2%, indicating synergism. The excess prevalence was greatest in children aged 6-17 years (15.3%), and it decreased with each older age category until it was absent in adults aged ≥ 55 years (-0.2%). In children, 94% of asthma cases attributable to the 2 factors were attributable to the interaction, whereas in the oldest adults, no cases were attributable to the interaction. CONCLUSIONS AND CLINICAL RELEVANCE: Interaction between atopy and an elevated eosinophil level in asthma cases was very strong in children but absent in the oldest adults, which suggests different mechanistic pathways for these factors by age and supports the notion that asthma is a heterogeneous disease. In addition, the age-dependent interaction between the factors has potential implications for the selection of asthma patients for treatments that would target either IgE or a high eosinophil level.

Effect of environmental allergen sensitization on asthma morbidity in inner-city asthmatic children.

BACKGROUND: Asthma causes significant morbidity in children, and studies have demonstrated that environmental allergies contribute to increased asthma morbidity. OBJECTIVE: We investigated the differences between allergen skin tests and specific IgE (SIgE) and the role of IgG in regards to allergen exposure levels, and asthma morbidity in inner-city children. METHODS: Five hundred and six serum samples from the National Cooperative Inner City Asthma Study (NCICAS) were evaluated for SIgE to cockroach (Blattella germanica), dust mite (Dermatophagoides farinae), and Alternaria as well as specific IgG (SIgG) and IgG(4) to cockroach (B. germanica) and total IgE levels. Associations between sensitization to these allergens, exposures, and asthma morbidity were determined. RESULTS: Sensitization to environmental allergens and total IgE correlated with increased health care and medication use, but not with symptoms of wheeze. Sensitization with exposure to cockroach was associated with increased asthma morbidity, whereas dust mite sensitization was correlated with asthma morbidity independent of exposure. There was also a strong correlation between SIgE levels and skin test results, but the tests did not always agree. The relationship between SIgE and asthma morbidity is linear with no obvious cutoff value. Increased Bla g 1 in the home was a good predictor for sensitization; however, this relationship was not demonstrated for Der f 1. Cockroach SIgG correlated with increased health care use, however, there was no modifying effect of SIgG or SIgG(4) on the association between cockroach SIgE and asthma morbidity. CONCLUSIONS: SIgE levels and skin prick test results to environmental allergens can serve as markers of severe asthma for inner-city children. Asthma morbidity increased in a linear manner with SIgE levels. IgG was not an important predictor or modifier of asthma morbidity.

Biological potency of German cockroach allergen extracts determined in an inner city population.

BACKGROUND: Cockroach allergy is an important cause of inner city asthma. To perform valid studies on the diagnosis and treatment of cockroach allergy, biological potencies of test extracts need to be established, and a surrogate in vitro test for biological potency should be chosen. METHODS: Sixty-two cockroach-allergic adult subjects were recruited for quantitative skin testing with three commercial German cockroach extracts. The intradermal D50 values were determined using linear interpolation, and the biologic potencies were determined from D50 data. The extracts were also analysed for relative potency, using a competition ELISA, and for specific allergen content, using a two-site ELISA. RESULTS: Estimates of each extract's D50 were analysable in 48-55 subjects, with D50s between 10.3 and 11.8. All three extracts were bioequivalent using pre-set criteria. The biological potencies of the extracts were 1738-8570 bioequivalent allergy units (BAU)/mL (geometric mean=3300), and these relative potencies were similar to those estimated by competition ELISA and specific allergen content. IgE against cockroach allergens were detected in sera from 34 subjects with analysable D50s, and 17 subjects had IgE directed against specific cockroach allergens. Although the presence of anti-Bla g 5 correlated with the subjects' skin test responses for 2/3 extracts, no single allergen was immunodominant. Antibody responses among the subjects were heterogeneous. CONCLUSIONS: Although commercial cockroach extracts are relatively low in potency, immunotherapeutic doses should be achievable. Biological potency may be estimated using D50 testing, a combination of specific allergen determinations, or by an overall potency assay such as the competition ELISA. CAPSULE SUMMARY: The biological potency of three German cockroach allergen extracts, determined in an inner city population, was 1738-8570 BAU/mL. No one allergen was immunodominant, and surrogate in vitro testing methods were examined.

Make induction day more effective - add a few problems.

INTRODUCTION: Induction courses are important to introduce Pre-Registration House Officers (PRHOs) to their new place of work. Traditionally, such programmes employ lectures, small group discussion and demonstrations. They let PRHOs meet members of various hospital disciplines and services. Since 1991, an interactive induction programme has been held each August for new PRHOs in the Eastern Region of Scotland taking up posts in Dundee Teaching Hospitals NHS Trust. DESIGN: Feedback from participants allows the course to be refined each year. In 1995, three paper-based patient management problems (PMPs) were included in the induction programme. Response was favourable. Most of the participants (82%) suggested the PMPs should be used again, but that more time should be allocated to enable them to tackle the problems. By August 1996, we aimed to provide a relevant and interactive programme that encouraged PRHOs to make immediate use of hospital resources. Two PMPs, in print format described likely case histories, with tasks that mirrored the junior doctors' forthcoming responsibilities. Healthcare team members and laboratory staff provided support as did study boards displaying written sheets of relevant clinical information. RESULTS: In the subsequent evaluation, the PMP component was rated highly by participants. They effectively triggered PRHOs to interact with hospital staff. CONCLUSIONS: We conclude that PMPs provide a valuable learning experience for junior doctors and are a useful addition to an induction day programme. We plan to refine and increase the use of PMPs in undergraduate and postgraduate settings.

Apparent dose equivalents resulting from severe heating of film dosimeters.

Unusual reported dose equivalents due to high-energy photons for two individuals prompted the investigation of the effects of severe heating conditions expected in closed vehicles during southwestern summer months on commercial film dosimeters. A historical review of dosimetry records revealed several additional reported high-energy photon exposures for individuals using only beta-emitting radioisotopes during hot summer months. Between 20-100% of experimentally heated badges had apparent dose equivalents exceeding the minimal detectable dose equivalent that were not flagged as being heat damaged or having unusual exposure patterns by the dosimetry companies. Reported dose equivalents for these badges were as high as 2.1 mSv.