title: [Effect of the time between symptom onset, swabbing and testing on the detection of influenza virus].
abstract: BACKGROUND
  Influenza surveillance requires the collection of nasopharyngeal swabs in Primary Care for testing in reference laboratories. We evaluated the influence on the laboratory results of the time since the onset of symptoms to swabbing (TSS) and from then until laboratory processing (TSL).
  
  
  METHODS
  We analysed swabs collected in the Sentinel Network of Navarra during the 2009-2010 influenza season. The samples were kept refrigerated until analysed by RT-PCR and viral culture. We analysed the percentage of positive swabs to influenza virus in accordance with the TSS and TSL by logistic regression.
  
  
  RESULTS
  From a total of 937 swabs, 373 (40%) were positive for influenza by RT-PCR. The TSS ranged from 0-15 days. In the adjusted analysis by period, laboratory and age, having a positive influenza culture decreased to less than half when the TSS was 4-5 days (OR=0.47; 95% CI, 0.24-0.94), and having a positive RT-PCR decreased when the TSS was 5 days or more (OR=0.24, 95% CI, 0.09-0.65). TSL does not significantly affect the result of the RT-PCR (OR by each day=0.96; 95% CI, 0.88-1.04), or the result of the viral culture (OR by each day=0.97, 95% CI, 0.89-1.06).
  
  
  CONCLUSIONS
  A TSS over 3 days reduced the likelihood of confirmation of influenza, affecting the viral culture more than the RT-PCR. A TSL within a range of two weeks had no significant effect on the results of the RT-PCR or the viral culture.
authors: Instituto de Salud Pública de Navarra, Pamplona, España. imartinba@navarra.es
authors: Iván
authors: I
authors: Martínez-Baz
authors: Gabriel
authors: G
authors: Reina
authors: Víctor
authors: V
authors: Martínez-Artola
authors: Mirian
authors: M
authors: Fernández-Alonso
authors: Esther
authors: E
authors: Salcedo
authors: Ana
authors: A
authors: Mazón
authors: Jesús
authors: J
authors: Castilla
mesh_terms: D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000175:diagnosis* / Q000821:virology*; D013997:Time Factors; D014773:Virology / Q000379:methods