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The importance of the relationship between asthma and allergy is now well-recognized [1‐7]. Studies of asthmatic patients with house dust mite allergy have demonstrated the importance of house dust mite avoidance measures in the control of asthma [8‐11]. MURRAY and FERGUSON [8] showed that a "sterile" bedroom environment was associated with marked improvement in children with asthma due to house dust mite allergy. In adults with the same condition, PLATTS-MILLS et al. [9] showed that airway responsiveness improved over a period of months in an allergen-free hospital environment. Residence at high altitude, where mite allergen levels are low, has also been used successfully in the treatment of asthma [10]. These and other unblinded, open studies in house dust mite-allergic patients have shown that aggressive measures to reduce house dust mite allergen exposure can improve asthma. Moreover, they suggest that sensitization and continuous exposure to an allergen are important risk factors for persistent asthma. Although sensitivity to specific allergens has, for a long time, been demonstrated in vivo by epicutaneous testing, it is only recently that measurement of levels of exposure to allergen (such as house dust mite and cat) has been performed. The production of monoclonal antibodies to these allergens has provided us with tools to assess exposure to the allergens more accurately, and also to assess the efficacy of intervention measures [12, 13]. During the past decade, most studies have measured levels of allergen in dust samples collected from a variety of reservoirs, such as mattresses and carpets, that may not accurately reflect the actual levels of exposure that patients have to the allergen. More recently, measurement of allergen levels in air samples of respirable dust particles have been carried out in an attempt to relate exposure and asthma severity [14, 15]. We now have the tools to study the dose-response relationship in order to better determine the levels of allergen exposure required for sensitization and for asthma exacerbations. Similarly, we should now be able to assess the change in allergen exposure with environmental control measures that is required to improve asthma. The article by VAN DER HEIDE et al. [16] in this issue of the Journal, attempts to address various aspects of allergen exposure and asthma. The authors have studied the effects of high-efficiency air cleaners and impermeable mattress coverings (a well-proven method) in reducing exposure to allergens and severity of asthma. Airway hyperresponsiveness was measured as a reflection of the severity of asthma. The authors demonstrated that "considerable amounts of airborne dust and allergenic particles were captured in the filters of the air cleaner". As with other studies, they found a significant decrease in house dust mite allergen from mattresses encased in an impermeable covering. Measurable house dust mite allergen was also entrapped at all levels of the air filters, but the amount of house dust mite allergen captured by the air filters was not related to the concentration in dust samples from the floor. The high efficiency particulate air (HEPA) component of the air filters captured cat allergen, even in homes without cats (at least in 60% of such homes). Improvement in airway hyperresponsiveness was found in the group treated with active air filters and mattress and pillow covers. A trend to improvement was also found in the group treated with mattress covers and inactive air filters. Thus, even in this relatively small group of allergic patients, the simple expediency of encasing one source of house dust mite allergen, the mattress, appears to have some impact on asthma. Of particular interest in this study is the multiple regression analysis, in which improvement in airway hyperresponsiveness was found to relate to exposure to textile floor covering (carpeting) in the living room, to companion animals in the homes, and to the ability to greatly reduce house dust mite allergen in the mattress. This finding confirms the notion that high levels of allergen exposure are important in sustaining airway hyperresponsiveness in asthma. Furthermore, it defines the presence of a reservoir for allergen (a companion animal in the home and/or the presence of carpeting) as a

Karlsson AS, Renstrom A, Hedren M, Larsson K. Allergy . 2004;59:661–667 To determine if feasible and economically defensible classroom interventions that do not interfere with pet ownership can alter airborne levels of cat allergen. Intermediate-level school classrooms ( n = 25, grades 1–6) in a suburb north of Stockholm, Sweden. Only classrooms with a single group of students using the class during the study period were used. Flooring materials, ventilation, cleaning routines, and room size were similar. The mean number of children per classroom was 25 (range: 18–30), and 21% had cats at home. …

Rationale Exposure to dog or cat allergen is believed to play an important role in the etiology of allergic disease; however, levels of these allergens have never been reported in a representative sample of U.S. homes. This study examined levels of Can f 1 and Fel d 1 in U.S. homes. Methods Data were obtained from the first National Survey of Lead and Allergens in Housing, a cross-sectional survey of 831 homes. Vacuum-collected dust samples from the bedroom bed, bedroom floor, living room floor, and living room sofa were analyzed for concentrations of Can f 1 and Fel d 1. Results All homes—100%—had a detectable level of Fel d 1 in at least one location while 99.9% had a detectable level of Can f 1. Geometric mean levels of each allergen were highest on the living room sofa—5.5 ug/g Can f 1 and 6.2 ug/g Fel d 1. Independent predictors of Can f 1 levels were race, Hispanic ethnicity, and an indoor dog. Independent predictors of Fel d 1 levels were census region, household income, race, Hispanic ethnicity, and an indoor cat. However, almost all of the explainable variation in allergen level was associated with the presence or absence of an indoor pet. Conclusions The potential for exposure to dog and cat allergens is present in essentially all U.S. homes. As one would expect, the presence of an indoor cat or dog is the major predictor of the pet allergen.

1. Gereda JE, Leung DY, Thatayatikom A, et al. Relation between house-dust endotoxin exposure, type 1 T-cell development, and allergen sensitization in infants at high risk of asthma. Lancet. 2000;355:1680-1683. 2. Sporik R, Squillace SP, Ingram JM, et al. Mite, cat, and cockroach exposure, allergen sensitization, and asthma in children: a case-control study of three schools. Thorax. 1999;54:675-680. 3. Perzanowski MS, Ronmark E, Platts-Mills TAE, Lundback B. Effect of cat and dog ownership on sensitization and development of asthma among preteenage children. Am J Respir Crit Care Med. 2002;166:696-702. 4. Crater DD, Heise S, Perzanowski M, Herbert R, Morse CG, Platts-Mills TAE. Asthma hospitalization trends in Charleston, South Carolina from 1956-1997. Pediatrics. 2001;108:E97. 5. Armstrong GL, Conn LA, Pinner RW. Trends in infectious disease mortality in the United States during the 20th century. JAMA. 1999;281:61-66. 6. Martin IR, Wickens K, Patchett K, et al. Cat allergen levels in public places in New Zealand. N Z Med J. 1998;111:356-358. 7. Weinberg EG. Urbanization and childhood asthma: an African perspective. J Allergy Clin Immunol. 2000;105:224-231.

Purpose of the Study. Leukotriene receptor antagonists have been shown to attenuate physiologic changes in the upper and lower airways induced by inhaled allergen challenge. This study looks at the effects of the oral leukotriene receptor antagonist zafirlukast on natural exposure to cat in patients with cat allergy. This study examines clinical, physiologic and inflammatory responses of the upper and lower airways. Study Population. Eighteen asthmatic patients between the age of 12 and 65 participated. All patients had a positive prick skin test to cat allergen and a positive response to a screening cat room challenge. At the time of study entry, all subjects were free of upper and lower respiratory tract symptoms. Methods. This …

VOLUME 109, NUMBER 1 method (Chromogenix AB*, Sweden). RESULTS: Using individual samplers, mean airborne endotoxin levels was 0.16 (+ or 0.19) ng/m3. Using static samplers, airborne endotoxin concentrations were 0,17 (+ or 0.15) ng/m3 in living-rooms and 0.19 (+ or -0.19) ng/m3 in bedrooms. 26 dwellings housed a pet animal. Among the studied factors, only the presence of animals caused significant increase in airborne endotoxin concentrations (i.e., mean of 0.22 ng/m3 compared to 0.14 ng/m3; p = 0.005). CONCLUSIONS: Our results suggest that: 1, Levels of airborne endotoxin found in domestic environment were comparable to those found in animal facilities and dramatically lower than those in swine confinement, poultry and cotton mills. 2. Presence of animals increased airborne endotoxin levels. 1 1 8 A New and Simple Method Used as Cleaning System for Mea suring Mite and Cat Allergens in Homes Simona Battucci*, Christelle Mazuet§, Aude Cahen§, Gabriele Peltre¥ *Procter & Gamble, Roma, Italy §Texcell, Institute Pasteur, Paris, France glnstitute Pasteur, Paris, France Mite and cat allergens are the most common indoor allergens present in homes. The majority of the population is regularly exposed to them in homes. Studies have usually determined levels of exposure through the analysis of dust samples collected by vacuuming house dust. The allergens collected in the dust bags are extracted in a liquid phase and quantified by ELISA. In this study, new disposable dry cloths developed by Procter & Gamble for their high dust collection capacity, Swiffer ®, were used for collecting and measuring allergens in laboratory testing and in real conditions. The dust and allergen binding capacity of Swifter was determined by adding increasing amounts of natural dust to a 16 cm 2 piece of Swiffer and extracting Der pl , Der fl and Fel dl allergen by rapid water extraction. Results showed that 16 cm 2 piece of Swifter (weighing approx 114 rag) is able to capture more than 210 nag of dust on one side. The allergen recovery after the first Swiffer water extraction was up to 81% of allergens. Up to 98% recovery can be achieved with two additional consecutive rapid water extractions. This confirms that no significant difference exists between the amount of allergens extracted from Swifter and the amount of allergens extracted from the dust. We also evaluated the Swiffer's efficiency at removing allergens from typical dusty domestic floors simulated by spraying standardized dust at a density of 340 mg/m 2. To assess the ability of Swifter to bind indoor allergens in real conditions, we conducted tests on Swifter cloths used to clean the floors in 40 homes in Italy, 10 homes in France, 20 homes in Spain, 10 in Portugal, 25 in Belgium. The cloths were wiped across flat, smooth floors made of tiles, marble or wooden parquet. An easy and rapid aqueous extraction of the dust was then performed to detect and quantify the maj or allergen of the Dermatophagoides pteronyssinus mite Der p 1, Dermatophagoides farinae Der f 1 and the major cat allergen Fel d 1. Results show that the two mite allergens are present in most of the homes at very different levels, independently of each other. Differences in the results obtained in different countries are most likely due to differences in local environment, climate conditions and life style. Cat major allergen Fel d 1 levels are high when a cat is present in the homes but still detectable in homes without cat. The results of these different tests show that Swiffer has a high dust and allergen uptake capacity for mites and cat allergens and the methodology used to extract allergens allows to obtain up to 80% with the first extraction, independently from the amount of dust collected and the level of allergens tested (Der p 1, Der f 1 and Fel d 1). 19 Identification of Preschool Children With Asthma J Berg*, GS Rachelefsky§, CA Jones', R McConnell¥, M Tichacek*, R Thompsont~, K Feliciano¥, DM ApodacalE *UCLA, Los Angeles, CA §Allergy Research Foundation Incorporated, Los Angeles, CA gUSC, Los Angeles, CA ~Los Angeles Unified School District, Los Angeles, CA The aim of this study was to facilitate the screening of low-income preschoolers for asthma and allergy. In an effort to aid asthma diagnosis and treatment, we surveyed parents of children that were enrolled in the Los Angeles Unified early education program. Ninety-nine early education centers participated in the survey. The survey is a seven-question instrument, developed for the Breathmobile TM by Dr. Craig Jones at LA countyUSC Medical Center. Surveys were initially returned from 74 centers and the return rate was 19.7%. Twelve centers had return rates of greater than 50%. The second phase of the surveillance will target the 25 centers that did not return any surveys with school supply incentives for teachers that encourage survey completion. Preliminary results indicate that 13% of the preschoolers missed 5 or more days of school per year for respiratory symptoms. Fourteen percent reported repeated episodes of difficulty breathing, with 11.7% having an ER visit or hospitalization during the past 2 years for respiratory symptoms. The majority of the sample was of Latino descent (71%) and had no insurance coverage. Few families had private or workrelated health insurance. Since the early diagnosis and treatment of asthma in preschool children can reduce life long asthma morbidity, school-based surveillance programs are a promising method of surveillance. '~ Prevalence of Asthma and Related Symptoms in Children and l lU I Adolescents From Public and Private Schools an ISAAC Study Susana RR Costa, Virginia Paes Leme Ferriani School of Medicine of Ribeir~o Preto-University of San Paulo, Ribeirao Preto, Brazil The ISAAC written questionnaire was applied to 3165 children aged 6-7 years old, and to 5504 adolescents aged 13-14 years old, registered in 38 public and 15 private schools in Ribeirao Preto, Southeast Brazil. In the group of 6-7 year-old children, the prevalence of wheezing ever, wheezing in the past year, diagnosed asthma, wheezing related to exercise and night cough were: 47.6%/42.8%; 23.7%/21.2%; 8.6%/6.8%; 6.7%/6.0%; 39.1%/36.9%, for boys and girls, respectively. Among the 13-14 year-old children, comparable prevalence results were: 35.9%/44.2%; 14.3%/18.8%; 8.8%/10.6%; 15.8%/17.0%; 25,4%/38.4% for boys and girls, respectively. We have also compared the frequency of positive answers to ISAAC questions No. 1, 2, 6, 7 and 8 among students from public and private schools, and the results are shown below. Overall, there was a significantly higher prevalence of asthma symptoms in adolescents from public schools, comprising children from lower socio-economical families. In keeping with studies in other parts of the world, comparison of reported symptoms and diagnosed asthma revealed significantly lower frequency of diagnosed asthma, suggesting that asthma is underdiagnosed in the population we have studied. It has been recently shown that the question "wheezing in the past year" is the best tool for discriminating asthmatic from non-asthmatic Brazilian children (Camelo-Nunes IC et al JACI 107:$230 abs 755, 2001). In keeping with this, the prevalence of asthma in Ribeirao Preto is 22.5% and 16.7% for 6-7 and 13-14 year-old children, respectively. These results are similar to those reported for other cities in Brazil, and indicate that prevalence of asthma in Brazil is comparable to the prevalence reported in developed countries.

A recent study in the Lancet shows that high levels of cat allergen in the home decrease the risk of asthma by altering the antibody response. It is known that exposure to high levels of house dust mites increases the production of IgE antibodies, but the same does not appear to be true of exposure to cat allergen. Thomas Platts-Mills and colleagues at the University of Virginia's Asthma and Allergic Diseases Center measured levels of cat allergen in the homes of 226 children, aged 12–14, 47 of whom had symptoms of asthma and bronchial hyper-reactivity. The levels of antibodies to dust mite and cat allergens, measured by isotype-specific (IgG and IgG4) radioimmunoprecipitation assays, were compared with sensitization to the allergen concentrations found in house dust. The researchers found an increased prevalence of sensitization and specific IgG antibody associated with increased exposure to dust mites. By contrast, they found that exposure to higher levels of cat allergen is associated with decreased sensitization but a higher prevalence of specific IgG. The authors conclude that, ‘…exposure to cat allergen can produce an IgG and IgG4 antibody response without sensitization or risk of asthma.’ Lancet (2001) 357, 752–756 HM

Ten asymptomatic patients with normal pulmonary function were selected for a double-blind trial of immunotherapy in cat-induced asthma. Each patient had a positive prick test to cat pelt extract and also a positive bronchial challenge response to the same extract. Patients were randomly assigned to active treatment or placebo groups and received weekly or biweekly injections over a 3 to 4-month period. The 5 patients who received the active treatment received a cumulative dose of cat pelt extract that ranged from 16.4 to 44.8 mg of total solid containing 1.7 to 4.7 mg of cat allergen 1. Apparent systemic reactions were observed in 3 patients who received the placebo and 3 patients who received the active treatment. The 5 patients who received the active treatment showed a reduction in skin reactivity to cat pelt extract as well as a significant mean reduction in bronchial sensitivity to the same extract. The 5 patients who received the placebo showed no significant changes in skin reactivity or bronchial sensitivity to cat pelt extract. Bronchial response to histamine did not change significantly in either the active treatment or the placebo groups.

The distribution of the major allergen of the domestic cat, cat allergen 1, was studied in 22 different tissues obtained from a male and female cat and in samples of saliva and urine. Of the cat tissues studied, only extracts of pelt and female brain contained amounts of cat allergen 1 in excess of 0.50 U/ml. Smaller amounts of cat allergen 1 were found in extracts of eye, thyroid, ovary, sublingual gland and large intestine. Unstimulated cat saliva contained a mean of 1.08 U/ml cat allergen 1. Saliva stimulated with ketamine HCl alone, or with ketamine HCl plus pilocarpine, contained 0.68–8.16 U/ml cat allergen 1. In all of the stimulated saliva collections, the total quantity of cat allergen 1 obtained was relatively constant (between 40 and 80 U). These results suggested that the elaboration of cat allergen 1 in saliva is independent of parasympathetic control. Cat allergen 1 could only be detected in cat urine that had been concentrated 9-fold in concentrations of less than 0.5 U/ml. The above results support the hypothesis that the major source of cat allergen 1 is the saliva, and that the presence of cat allergen 1 in the pelt is due to deposition of the allergen during grooming.

The commercial cat and dog allergen extracts are traditionally prepared from pelt, fur or dander. However, there is increased evidence of the allergenicity of saliva and urine of the animals. We have investigated 25 asthmatic children with a positive cat and/or dog RAST result. All 20 subjects with a positive cat RAST gave a positive skin prick test result to cat saliva, cat urine and cat hair. Analogously, all 20 subjects with a positive dog RAST had a positive skin reaction to dog saliva, urine and dander. In RAST inhibition experiments with dog and cat allergen discs, dog saliva appeared to be at least as potent as a commercial dog dander and hair extract, while cat saliva was less potent than the respective commercial extract. Both dog and cat salivas were clearly more potent than the respective urine. Significant cross-reactivity was observed between cat hair and dog dander in the RAST inhibition, whereas saliva and urine were shown to be more species-specific. An experimental dog dander preparation had about the same specificity as, and even higher allergenic activity than, that of dog saliva or urine. Our results suggest that saliva actually may be the best source of cat and dog allergen preparations. The importance of urine warrants further investigation.

Several mouse monoclonal antibodies (MAbs) were obtained which specifically recognized allergen molecules from cat dander extract. Two of them (C5.8 and C5.24) were specific for the main cat allergen, Fel d I. One (C5.25) recognized an important allergen with approximate molecular weight of 30000 Da and a pI between 3.9 and 4.3. A third group of MAbs comprised several hybridomas which were specific either for cat albumin or cat immunoglobulin. The immunochemical characterization and the clinical significance of the cat dander components recognized by these MAbs is presented and discussed.

Thirty homes in Rochester, Minn., 20 of which housed cats, were studied to compare cat and mite allergen concentrations in airborne and settled dust. With Air Sentinels in the bedroom and living room for airborne collections, and a Sample Vac for collections from living room carpet and bedroom mattress, immunochemical quantifications of each were made with various radiometric assays with polyclonal and monoclonal antibodies. The most significant correlations were found between airborne mite in the bedroom and living room (p less than 0.001) and airborne mite in the bedroom and dust from the bedroom mattress (p less than 0.001). Most houses had specific epitopes of both Dermatophagoides pteronyssinus and D. farinae, but D. farinae was present in greater amounts. In seven houses we found greater than 10 micrograms of group I mite allergen per gram of settled dust, indicating that some houses in Minnesota have concentrations of mite allergens high enough to cause allergic disease, even in the winter. Clinical interpretation of these data on air levels is hampered by uncertainty as to whether symptoms are more closely related to average steady-state exposure, which we measured, or to brief heavy concentrations. Further epidemiologic studies are needed to define the concentration of mite and cat allergens in the air that are risk factors for allergic disease. The concentration of cat allergen correlated with mite allergen in the air, but not in settled dust, presumably reflecting the fact that both are influenced by ventilation rate.

In direct RAST analyses of sera from 43 individuals with a history of cat allergy, 39.5% were positive to cat pelt, 37.5% to cat saliva, and 12% each to cat urine and serum. The cat pelt and saliva extracts contained allergen 1, but cat serum and cat urine collected by bladder puncture had no detectable levels of this allergen. A crossed immunoelectrophoresis/crossed radioimmunoelectrophoresis analysis failed to reveal any allergen in urine or serum that was not also present in the saliva or pelt preparations, although urine had two allergens not present in serum. When serum from a patient who was direct RAST positive to cat pelt, serum, saliva, and urine was tested by crossed radioimmunoelectrophoresis, it was determined that a total of six allergens were detectable in cat pelt, three in cat urine, and six in cat serum. Since cat serum contains no detectable cat allergen 1, it may be concluded that at least seven allergens derived from the cat are capable of binding to IgE antibody in humans.

The potency of commercial dog and cat allergen extracts produced by different firms may vary by a factor which may range from several 100 to more than 1,000. In cat extracts, major common components can be demonstrated between pI 4.5–5.0. In addition to these, additional components were seen in the pI ranges 3.0–3.9; 5.3; and 7.5–8.5. In commercial dog extracts, major common components were detected between pI 4.3–4.7. In one dog extract, the presence of additional components with pI 3.0–3.4; 3.5–3.7; 3.9–4.1; 4.9–5.0; 5.1 and 5.2–5.3 was demonstrated. There are indications, that in the sera of allergic patients, IgE antibodies are present which are counterparts of breed-specific allergens.

Eighteen lots of house dust extract from nine commercial sources (obtained as weight per volume or protein nitrogen unit per cubic centimeter) were analyzed for cat allergen content by direct quantitative immunoelectrophoresis after concentration. Cat allergen 1 was measurable (>0.3 units) in 11 extracts with a mean (range) of 5.8 (1.3 to 31.0) U/gm of source material. Cat albumin was measurable (>2.4 units) in 12 extracts with a mean (range) of 53.4 (11.5 to 319.7) U/gm. In order to evaluate whether the cat allergen 1 content is a significant contribution to the allergenic activity of the extract, 17 cat-allergic subjects were tested by prick test with a purified preparation of cat allergen 1. The mean (range) concentration that produced a 3 mm wheal was 0.01 (0.0013 to 1.33) U/ml. Therefore, the commerical house dust extracts studied, when these extracts were diluted to a concentration commonly used for prick testing, would frequently contain enough cat allergen 1 to produce strong prick test reactions in cat-allergic subjects. It is difficult to justify the use of such commerical dust extracts as diagnostic reagents. For comparison purposes, nine dust samples from an apartment housing two cats were similarly analyzed. Cat allergen 1 was measurable in seven samples with a mean (range) of 23.8 (1.8 to 64.3) U/gm. Cat albumin could be measured in all nine samples with a mean (range) of 32.3 (0.16 to 70.8) U/gm. The average amount of cat allergen 1 that could be washed off the surface of the cats was 270 units. Large reservoirs of cat allergen 1 were present. The spread on which the cats commonly slept contained 20,000 units of cat allergen 1. Contamination of a pool of house dust samples with dust from a cat-containing environment would likely be significant.

The available methods for controling dust mites in houses consist of washing bedding regularly, covering mattresses, and, when possible, removing carpets. This leaves the problem of fitted carpets in living rooms, as welt as the problem of sofa and chair upholsteries. These can be improved by vacuum cleaning, controling humidity, and perhaps using certain acaricides. However, there is no perfect regime and very inadequate data on the results of different measures. Control of other allergens in house dust requires intelligent observation and persistence~ Cat allergen may take months to remove. Fungal allergens are still poorly defined, but can be helped by cleaning measures, reducing humidity, and removing plants. Pollen can definitely enter house dust in significant quantities and it may be important to encourage air conditioning during the pollen seasons to reduce this. Although cockroaches are almost certainly an important cause of asthma, very little is known about the factors that influence the quantities of cockroach allergens in houses.

To evaluate the effect of cat removal on cat-allergen content in the home, serial house dust samples were collected from 15 homes during a 9- to 43-week period after cat removal. Samples were obtained with a hand-held vacuum cleaner, and allergen content was quantitated by a radioimmunoassay specific for the major cat allergen, Fel d I. Baseline Fel d I content ranged from 7.8 Food and Drug Administration units per gram of dust to 436.7 U/gm (median 61.2 U/ gm), consistent with levels found in homes with a pet cat. Fel d I levels declined gradually in most homes, and by 20 to 24 weeks after cat removal, eight of 15 reached levels consistent with levels found in control homes without cats. In two of those homes, allergen levels fell much more rapidly after aggressive environmental control measures were undertaken. In the other seven homes, however, the decline occurred at a much slower rate, with three homes demonstrating persistent elevations in Fel d I content for 20 or more weeks. These data demonstrate that the task of allergen elimination from an indoor environment is extremely difficult, even when the source of a specific allergen can be identified and removed.

A two-site solid-phase radioimmunoassay has been developed for the quantitation of the main cat allergen, Fel d I or cat allergen 1. The assay is based on two different monoclonal antibodies which recognize different epitopes on the Fel d I molecule; one antibody (C5/24) was immobilized on the solid phase and the other (C5/8) was labeled with 125I, being the allergen molecule sandwiched between them. The assay is specific for the Fel d I molecule and sensitive enough to detect as little as 0.25 ng/ml of allergen. The Fel d I RIA was compared with a radial immunodiffusion technique for the determination of allergen levels in several cat extracts and a good quantitative correlation was found. The same good correlation was found when the results obtained with the Fel d I RIA were compared with the determination of the total allergenic activity by RAST inhibition. The results indicate that the MAb RIA could be very useful in the standardization of allergenic extracts from feline origin.

Exposure to indoor allergens is an important risk factor for sensitisation and respiratory allergy. The aim of this paper was to evaluate the levels of mite, cat and latex allergens in dust collected from an indoor workplace and to assess whether the exposure to these allergens was associated with the allergy symptoms reported by employees. Sixty dust samples were collected. Allergen concentrations were measured with antibody based ELISAs. All 144 participants compiled a questionnaire exploring possible symptoms of allergy. No association between latex allergen exposure and symptoms was found in spite of the high frequency of latex allergens. Mite allergens were detected in a minority of rooms. Cat allergen was the most important indoor allergen in the sampled workplace and exposure to this allergen could represent a risk for employees.

Summary Exposure to cat and/or cat allergens can confer either an increase in risk, or protection, or will have no effect, depending on the age of the assessment, study design and the choice of study population.

Few data are available from Eastern Mediterranean countries about levels of domestic allergens and endotoxins. Dust samples were collected from mattresses and floors of 457 homes in the Syrian city of Aleppo and analysed for antigens and endotoxins. The most important predictors for detectable levels of house-dust mite allergen Der p 1 were Arabic-style houses (OR 3.21) and newer houses (OR 1.56). In homes without cats, rubber mattresses were associated with detectable cat allergen Fel d 1 in mattress dust (OR 1.6). Cockroach allergen Bla g 2 was significantly more likely to be detected in houses over 20 years old than newer houses. Endotoxin levels were significantly higher in wool/cotton mattresses and older houses.

Validated instruments are not available to assess the residential characteristics. The aim of this study was to assess the reliability and validity of an interviewer-administered home visit report. The validity of 48 items in the Home Visit Report was examined against: observations made by a researcher, measurements of relative humidity, cat allergen, and ergosterol, a biomaker of fungal exposure and a biochemical test. Test-retest reliability of 10 fixed residential characteristics was assessed comparing the responses obtained in the main study with the pilot study, Kappa, ANOVA and Wilcoxon Rank Sum tests were applied to assess the agreement and P < 0.05 was considered as statistically significant. Among 44 items examined for the validity against observations, there was a perfect or almost perfect agreement in 21 (kappa = 0.9-1) and substantial agreement (kappa = 0.6-0.8) in 19. Higher cat allergen levels were observed with cat ownership and cat being allowed indoors. Observed condensation was associated with relative humidity and observed mould was associated with ergosterol levels. The agreement on the type of carpet and the test was substantial (kappa = 0.6). Among 10 items examined for reliability, there was a perfect or almost perfect agreement in 9 (kappa = 0.9-1) and substantial agreement (kappa = 0.7) in one. In conclusion, the Home Visit Report validated in this study provides reliable and valid data.