A. Vérot

Dust and airborne exposure to allergens derived from cockroach (Blattella germanica) in low-cost public housing in Strasbourg (France)

BACKGROUND Although a strong association between allergy to cockroach (CR) and asthma has been observed in the United States and Asia, there are little data about the extent of exposure to CR allergen in Europe. OBJECTIVE To determine the levels of CR allergens in dust samples from apartments in Strasbourg and to determine the concentration and size of CR allergens in the air. METHODS Nine apartments in a public housing complex were chosen on the basis of visual evidence of CR infestation. Levels of CR allergens (Bla g 1 and Bla g 2) in kitchen and mattress dust samples were measured by immunoassay with the use of monoclonal antibodies. Air was sampled for 3 to 8 hours in the kitchen under undisturbed conditions, during artificial disturbance, and during normal domestic activity by using an impinger and a parallel glass fiber filter and at flow rates of 2 to 20 L/min. Airborne CR and mite allergens were measured concurrently in the bedroom of one apartment before, during, and after artificial disturbance. RESULTS High levels of Bla g 1 and Bla g 2 were found in kitchen dust from the nine apartments (geometric means of 3919 U/gm [range 530 to 14306 U/gm] and 497 U/gm [range 73 to 1946 U/gm], respectively). Under undisturbed conditions, airborne CR allergens were not detectable in any of the apartments. During vigorous artificial disturbance, Bla g 1 and Bla g 2 were detectable in air samples from seven apartments (geometric means of 4.5 U/m3 [range 0.7 to 17.2 U/m3] and 1.0 U/m3 [range 0.4 to 3.4 U/m3], respectively). Both allergens were predominantly collected on the first stage of the impinger, and 76% to 80% of the airborne allergen was associated with particles greater than 10 microns in diameter. The levels were significantly higher than those collected on the second or third stages of the impinger (p < 0.001). A comparison of the levels of mite and CR allergens showed that the airborne properties of these allergens were similar, that is, measurable only during disturbance and not detectable 30 minutes after disturbance. CONCLUSION Levels of CR allergen in low-cost public housing in Strasbourg can be as high as or higher than the levels measured in towns in the United States. CR allergens become airborne during disturbance and are primarily associated with particles greater than 10 microns in diameter. Patients with asthma living in urban areas of Europe in housing prone to CR infestation should be evaluated for sensitization and exposure to CR allergens.

Receiver Operating Characteristic analysis: A useful method for a comparison of the clinical relevance of two in vitro IgE tests

BACKGROUND The objectives of this study were to demonstrate the usefulness of Receiver Operating Characteristic (ROC) analysis in the definition of a positive threshold in the comparison of two in vitro tests for detecting IgE antibodies and to determine the clinical relevance of specific IgE tests according to the sensitivity and specificity determined by ROC analysis. METHODS Specific IgE levels were compared with the use of both MATRIX (Abbott Laboratories, Chicago, Ill.) and PHADEZYM (Pharmacia, Uppsala, Sweden) tests in 109 patients: 86 allergic patients and 23 control subjects. All allergic patients had a clinical history of allergy to mite, cat, grass pollen, or birch pollen and positive skin prick test results to the suspected allergen. Using various levels of specific IgE, we determined the points of the ROC curves with the best ratio of true positives to false positives for four aeroallergens (i.e., mite, cat, grass pollen, and birch pollen). RESULTS Except for mite allergen there was no correspondence between the positive threshold values determined by ROC analysis with MATRIX and PHADEZYM tests. In terms of class, when ROC analysis was used, the threshold was class III with the MATRIX test and class II with PHADEZYM test for cat, grass pollen, and birch pollen and class III for mite. According to the threshold value, sensitivity and specificity for MATRIX and PHADEZYM tests were similar except for cat, for which the PHADEZYM test had a lower sensitivity (0.71) than the MATRIX test (0.90). With mite allergen the predictive value of only one positive MATRIX test result was 0.96. The specificities of MATRIX and PHADEZYM tests were 100% in both nonatopic and atopic control groups. CONCLUSIONS We conclude that ROC analysis is a reliable method for comparing IgE in vitro tests and that it emphasizes the lack of correspondence between arbitrary units given for each in vitro test. ROC analysis appears to be a good method for helping to standardize IgE in vitro tests.

Urticaria and Rhinitis to Shrubs of Ficus benjamina and Breadfruit in a Banana-Allergic Road Worker: Evidence for a Cross-Sensitization between Moracea, Banana and Latex

Background: We report the case of a road worker with a food allergy to banana, who developed urticaria and rhinitis when cutting shrubs of Ficus benjamina and breadfruit. He did not develop an allergy to latex of Hevea brasiliensis.Results: Sensitization to latex of F. benjamina, H. brasiliensis, breadfruit and banana was demonstrated using skin tests and specific IgE measurements. RAST inhibitions procedures showed that specific IgE to breadfruit latex cross-reacted more strongly with latex of H. brasiliensis and banana than with latex of F. benjamina with the same extract. Conclusion: Given the wide distribution of Moracea trees in tropical regions, sensitization to latex of H. brasiliensis and banana could be a consequence of sensitization to Moracea members; F. benjamina does not seem to be the only Moracea responsible for cross-allergy with latex and fruit. Consequently, it seems interesting to test other members of the Moracea family in patients sensitized to latex of H. brasiliensis and banana. Sensitization to breadfruit could be a risk factor for sensitization to latex of H. brasiliensis.

Controlling Indoor Mite Exposure: The Relevance of the Acarex Test

The Acarex test is an easy, rapid and cost-effective means of assessing exposure to house dust mites. The present study was designed to evaluate the correlation between the Acarex test using a 4-point and a 7-point scale and the major allergens content (Der p1 + Der f1) of house dust samples measured by an ELISA technique and also to assess the validity of the test with regard to both sampling and reading of the colour scale. Some 719 house dust samples from patients’ homes were evaluated using the supplied 4-point scale (classes 0, 1, 2, 3) and again with interpolation of 3 intermediate scale points (classes 0.5, 1.5, 2.5) and Der p1 + Der f1 content using ELISA. Reliability of sampling was studied in 39 dwellings comparing results obtained by householders and technicians. Reproducibility of reading the colorimetric scale was evaluated in 3 trained technicians and 15 untrained people. The correlation between the Acarex and the ELISA results was 0.68 (p ! 0.0001) with class 0 reliable for assessing low allergen levels, class 1 unable to discriminate, and classes 2 and 3 reflecting high allergen levels (class 3 identified 94.2% of samples with an allergen content greater than 10 Ìg Wg–1). Discrepancies between Acarex scores for samples collected by patients and those collected by technicians did not exceed half a scale point. Reproducibility of reading by trained technicians gave intraindividual and interindividual coefficients of variation of 0% for classes 0 and 3 and about 20% or more for the other classes. On average readings by untrained participants had 42% discrepancies, mostly in classes 1 and 2. We conclude that the Acarex test is a useful home test whether used by patients or technicians; misclassifications of colour readings were less frequent at the scale extremes. Copyright