The role of respiratory viruses in cystic fibrosis.
BACKGROUND
Previous studies have suggested a role played by respiratory viruses in the exacerbation of cystic fibrosis (CF). However, the impact of respiratory viruses could have been underestimated because of the low detection rate by conventional laboratory methods.


METHODS
Children with CF had nasal swabs and sputum samples obtained on a routine basis and when they developed respiratory exacerbations. Nucleic Acid Sequence Based Amplification (NASBA) was used to detect respiratory viruses from nasal swabs. The definition of a respiratory exacerbation was when the symptom score totalled to 4 or more, or if the peak expiratory flow fell by more than 50 l/min from the child's usual best value, or if the parent subjectively felt that the child was developing a cold.


RESULTS
71 patients had 165 reported episodes of respiratory exacerbations. 138 exacerbation samples were obtained of which 63 (46%) were positive for respiratory viruses. In contrast, 23 of 136 asymptomatic nasal swabs (16.9%) were positive for respiratory viruses. There was significantly more viruses being detected during respiratory exacerbations, in particular influenza A, influenza B and rhinovirus (p<0.05). Upper respiratory symptoms significantly correlated with positive respiratory viral detection (p<0.05). This study also showed that viral respiratory exacerbations in CF could be independent from bacterial infections.


CONCLUSIONS
Respiratory viruses are associated with exacerbations in CF and upper respiratory symptoms are strong predictors for their presence. 'Real-time' NASBA has a rapid turn-around time and has the potential to aid clinical decision making, such as the use of anti-virals and administration of antibiotics.
Wat
Dennis
D
Department of Cystic Fibrosis, University Hospital of Wales, Cardiff, UK. Electronic address: denniswat118@hotmail.com.
Gelder
Colin
C
Llandough Hospital, Penarth, UK.
Hibbitts
Sam
S
University of Wales College of Medicine, Cardiff, UK.
Cafferty
Fay
F
Papworth Hospital, Cambridge, UK.
Bowler
Ian
I
Royal Gwent Hospital, Newport, UK.
Pierrepoint
Marcus
M
Neville Hall Hospital, Abergavenney, UK.
Evans
Rachel
R
Singleton Hospital, Swansea, UK.
Doull
Iolo
I
Department of Cystic Fibrosis, University Hospital of Wales, Cardiff, UK.
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000821:virology*; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000302:isolation & purification; D009981:Influenza B virus / Q000302:isolation & purification; D021141:Nucleic Acid Amplification Techniques; D011024:Pneumonia, Viral / Q000150:complications* / Q000175:diagnosis; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000150:complications / Q000175:diagnosis / Q000821:virology*; D012229:Rhinovirus / Q000302:isolation & purification