title: Synergism between allergens and viruses and risk of hospital admission with asthma: case-control study.
abstract: OBJECTIVE
  To investigate the importance of sensitisation and exposure to allergens and viral infection in precipitating acute asthma in adults resulting in admission to hospital.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Large district general hospital.
  
  
  METHODS
  60 patients aged 17-50 admitted to hospital over a year with acute asthma, matched with two controls: patients with stable asthma recruited from the outpatient department and patients admitted to hospital with non-respiratory conditions (inpatient controls).
  
  
  METHODS
  Atopic status (skin testing and total and specific IgE), presence of common respiratory viruses and atypical bacteria (polymerase chain reaction), dust samples from homes, and exposure to allergens (enzyme linked immunosorbent assay (ELISA): Der p 1, Fel d 1, Can f 1, and Bla g 2).
  
  
  RESULTS
  Viruses were detected in 31 of 177 patients. The difference in the frequency of viruses detected between the groups was significant (admitted with asthma 26%, stable asthma 18%, inpatient controls 9%; P=0.04). A significantly higher proportion of patients admitted with asthma (66%) were sensitised and exposed to either mite, cat, or dog allergen than patients with stable asthma (37%) and inpatient controls (15%; P<0.001). Being sensitised and exposed to allergens was an independent associate of the group admitted to hospital (odds ratio 2.3, 95% confidence interval 1.0 to 5.4; P=0.05), whereas the combination of sensitisation, high exposure to one or more allergens, and viral detection considerably increased the risk of being admitted with asthma (8.4, 2.1 to 32.8; P=0.002).
  
  
  CONCLUSIONS
  Allergens and viruses may act together to exacerbate asthma.
authors.affiliation: North West Lung Centre, Wythenshawe Hospital, Manchester M23 9LT.
authors.forename: Rosalind M
authors.initials: RM
authors.lastname: Green
authors.forename: Adnan
authors.initials: A
authors.lastname: Custovic
authors.forename: Gwen
authors.initials: G
authors.lastname: Sanderson
authors.forename: Jenny
authors.initials: J
authors.lastname: Hunter
authors.forename: Sebastian L
authors.initials: SL
authors.lastname: Johnston
authors.forename: Ashley
authors.initials: A
authors.lastname: Woodcock
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000009:adverse effects* / Q000276:immunology; D001249:Asthma / Q000276:immunology* / Q000821:virology*; D016022:Case-Control Studies; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006760:Hospitalization; D006801:Humans; D007114:Immunization; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014777:Virus Diseases / Q000150:complications*
chemical_list: D000485:Allergens