title: Cat and house dust mite allergen content is stable in frozen dust over time.
abstract: BACKGROUND
  Dust from indoor environments consists of animal allergens, pollen, endotoxins, and other substances which may exacerbate symptoms in sensitive individuals. In prospective cohort studies, dust is often collected from indoor environments in order to assess allergen exposure and possible relationships to health outcomes. Typically, large numbers of samples are collected and kept frozen until further analysis, sometimes several years later. To date, there is insufficient knowledge about what happens to the dust and its contents during storage.
  
  
  OBJECTIVE
  In the present study, our aim was to analyze allergen content over a 30 month period frozen dust collected from beds in homes in order to simulate a study design of exposure assessment commonly used in epidemiological studies.
  
  
  METHODS
  Thirty-seven dust samples from mattresses in homes were collected using a Duststream dust collector. Each dust sample was subdivided into six aliquots. One tube (baseline) was extracted and analyzed for cat and house dust mite (HDM) allergen content using ELISA, all other tubes were stored at -80 °C until further handling. Approximately every six months (6, 12, 18, and 30 months), dust from one tube was thawed, extracted and analyzed the same way. Data was log-transformed and analyzed using linear regression.
  
  
  RESULTS
  No trend for decreasing or increasing cat (p = 0.606) or HDM (p = 0.928) allergen levels could be observed over time. Levels of cat allergen were considerably higher in mattresses from homes with cats compared to homes without cats (p < 0.001).
  
  
  CONCLUSIONS
  It is important to assess the allergen stability in dust before designing costly and labor-intensive studies of allergen exposure and health outcomes, commonly used in environmental epidemiology. Although the present study showed that cat and HDM allergens remained stable in dust stored at -80 °C during a 2.5 year period, analyses of other allergens or substances in frozen dust and evaluating the effect of longer storage times is desirable.
authors.affiliation: Karolinska Institutet, Institute of Environmental Medicine, Stockholm, Sweden. anne-sophie.merritt@ki.se
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Merritt
authors.forename: Niklas
authors.initials: N
authors.lastname: Andersson
authors.forename: Catarina
authors.initials: C
authors.lastname: Almqvist
mesh_terms: D000485:Allergens / Q000032:analysis*; D000818:Animals; D039741:Antigens, Dermatophagoides / Q000032:analysis*; D002415:Cats; D004391:Dust / Q000032:analysis*; D005615:Freezing; D006801:Humans; D013997:Time Factors
chemical_list: D000485:Allergens; D039741:Antigens, Dermatophagoides; D004391:Dust