This study was conducted to examine the impact of building characteristics and indoor air quality on recurrent wheezing in infants. We followed a birth cohort (BAMSE) comprising 4089 children, born in predefined areas of Stockholm, during their first 2 years of life. Information on exposures was obtained from parental questionnaires when the children were 2 months and on symptoms and diseases when the children were 1 and 2 years old. Children with recurrent wheezing, and two age-matched controls per case, were identified and enrolled in a nested case-control study. The homes were investigated and ventilation rate, humidity, temperature and NO2 measured. We found that living in an apartment erected after 1939, or in a private home with crawl space/concrete slab foundation were associated with an increased risk of recurrent wheezing, odds ratio (OR) 2.5 (1.3-4.8) and 2.5 (1.1-5.4), respectively. The same was true for living in homes with absolute indoor humidity >5.8 g/kg, OR 1.7 (1.0-2.9) and in homes where windowpane condensation was consistently reported over several years, OR 2.2 (1.1-4.5). However, air change rate and type of ventilation system did not seem to affect the risk. In conclusion, relatively new apartment buildings, single-family homes with crawl space/concrete slab foundation, elevated indoor humidity, and reported wintertime windowpane condensation were associated with recurrent wheezing in infants. Thus, improvements of the building quality may have potential to prevent infant wheezing.

Sensitization to house dust mites, storage mites and other common inhalation allergens was studied in 144 farmers using SPT and RAST. The study population was selected from a random sample of 808 farmers and consisted of 47 persons who had declared themselves to suffer from asthma, 63 persons who had reported respiratory symptoms, and 34 healthy persons without respiratory symptoms. The most prevalent RAST was towards storage mites and was found in 17% of farmers who suffered from asthma and was estimated to occur in 5% of the random sample of farmers. A positive RAST to house dust mites was found in 17% of farmers who reported to suffer from asthma. Sensitization to pollens, animal dander and grain species was rare. A positive RAST to moulds was not found. There was a strong association between a positive RAST to house dust mites and a positive RAST to storage mites (odds ratio 21.0). A positive RAST to storage mites was significantly associated with living in a dwelling in the past which was recalled as damp (odds ratio 4.9). A high number of house dust mites was found in nearly all dwellings (median count 148 mites/0.1 g dust) and a high number of storage mites was found in some dwellings. This study suggests that in humid and temperate regions of Europe, allergy to storage mites in farmers is not caused exclusively by occupational exposure but damp housing conditions and indoor exposure to storage mites may also be important.

An epidemiological study was performed with a self administered questionnaire in a representative sample of 1685 Danish farmers. The purpose of the study was to assess the prevalence of self reported asthma, wheezing during work, and symptoms of chronic bronchitis and to evaluate possible risk factors for the development of these symptoms. A response rate of 73-3% was obtained. The prevalence ofasthma was 7 7% and ofchronic bronchitis 23 6% in responders. The prevalence of asthma and chronic bronchitis increased from 3-6% and 17-9% in 31-50 year old farmers to 11 -8% and 33 0% in 51-70 year old farmers, and from 5-5% and 17 5% in dairy farmers to 10-9% and 32-0% in pig farmers. A logistic regression analysis with correction for age and smoking habits confirmed that pig farming was a risk factor for asthma (odds ratio 2 03), chronic bronchitis (odds ratio 1 53), and wheezing during work (odds ratio 3-33).

The concentration of house-dust mites (Dermatophagoides spp.) was investigated for four seasons in three locations in each of 50 Danish apartments. Simultaneously the absolute humidity was recorded and the previously known correlation between mite counts and indoor humidity was confirmed. It appeared, however, that apartments which had a low absolute indoor humidity in the winter period (due to low household load of water vapour) did not contain noticeable concentrations of house-dust mites in the summer and autumn despite the fact that the indoor absolute humidity in these apartments could be high enough to allow for a high peak-population of mites. Because of this it is suggested that in a temperate climate avoidance measures against house-dust mites should be supplemented at least by a drying out period in the winter, when this process is convenient to perform because of the low outdoor absolute humidity.

BackgroundStreptococcus pneumoniae and Haemophilus influenzae cause pneumonia and as Neisseria meningitidis they are important agents of meningitis. Although several PCR methods have been described for these bacteria the specificity is an underestimated problem. Here we present a quantitative multiplex real-time PCR (qmPCR) for detection of S. pneumoniae (9802 gene fragment), H. influenzae (omp P6 gene) and N. meningitidis (ctrA gene). The method was evaluated on bronchoalveolar lavage (BAL) samples from 156 adults with lower respiratory tract infection (LRTI) and 31 controls, and on 87 cerebrospinal fluid (CSF) samples from meningitis patients.ResultsThe analytical sensitivity was not affected by using a combined mixture of reagents and a combined DNA standard (S. pneumoniae/H. influenzae/N. meningitidis) in single tubes. By blood- and BAL-culture and S. pneumoniae urinary antigen test, S. pneumoniae and H. influenzae were aetiological agents in 21 and 31 of the LTRI patients, respectively. These pathogens were identified by qmPCR in 52 and 72 of the cases, respectively, yielding sensitivities and specificities of 95% and 75% for S. pneumoniae, and 90% and 65% for H. influenzae, respectively. When using a cut-off of 105 genome copies/mL for clinical positivity the sensitivities and specificities were 90% and 80% for S. pneumoniae, and 81% and 85% for H. influenzae, respectively. Of 44 culture negative but qmPCR positive for H. influenzae, 41 were confirmed by fucK PCR as H. influenzae. Of the 103 patients who had taken antibiotics prior to sampling, S. pneumoniae and H. influenzae were identified by culture in 6% and 20% of the cases, respectively, and by the qmPCR in 36% and 53% of the cases, respectively.In 87 CSF samples S. pneumoniae and N. meningitidis were identified by culture and/or 16 S rRNA in 14 and 10 samples and by qmPCR in 14 and 10 samples, respectively, giving a sensitivity of 100% and a specificity of 100% for both bacteria.ConclusionsThe PCR provides increased sensitivity and the multiplex format facilitates diagnosis of S. pneumoniae, H. influenzae and N. meningitidis and the assay enable detection after antibiotic treatment has been installed. Quantification increases the specificity of the etiology for pneumonia.