Use of induced sputum for the diagnosis of influenza and infections in asthma: a comparison of diagnostic techniques.
BACKGROUND
Influenza (Flu) and respiratory syncytial virus (RSV) are important viral pathogens that cause lower respiratory tract infections and severe exacerbations of asthma. Molecular biological techniques are permitting a rapid and accurate diagnosis of infections caused by respiratory pathogens, and have typically been applied to upper respiratory samples. Sputum induction provides an opportunity to directly sample secretions from the lower respiratory tract.


OBJECTIVE
To determine the role of induced sputum reverse-transcription polymerase chain reaction (RT-PCR) in the detection of respiratory pathogens and compare this with detection using serology and immunofluorescent antigen (IFA) testing, we recruited 49 adults from emergency room with exacerbations of asthma. After a medical assessment and spirometry, sputum was induced using ultrasonically nebulised normal saline. Sputum was assayed using IFA and RT-PCR for flu and RSV. Flu serology was performed acutely and at convalescence, 4-5 weeks later.


RESULTS
Influenza A or B was detected in 24% of the samples by PCR, significantly more than the nine cases detected using serology and the one case using IFA (P<0.05). RSV was detected in 37% of samples using PCR and 20% by IFA (P<0.05).


CONCLUSIONS
The combination of induced sputum and RT-PCR provides a useful means of detecting respiratory infection. The technique is safe in both adults and children, and RT-PCR is more sensitive than conventional serology and IFA. The improved sensitivity of induced sputum RT-PCR also permits a more rapid diagnosis and the opportunity of early administration of effective treatments.
Simpson
Jodie L
JL
Department of Respiratory and Sleep Medicine, John Hunter Hospital, Locked Bag 1, Hunter Region Mail Centre, Newcastle, New South Wales 2310, Australia.
Moric
Ivana
I
Wark
Peter A B
PA
Johnston
Sebastian L
SL
Gibson
Peter G
PG
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000032:analysis; D001249:Asthma / Q000150:complications*; D003168:Complement Fixation Tests; D003199:Computer Systems; D003289:Convalescence; D004630:Emergencies; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D009981:Influenza B virus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D007251:Influenza, Human / Q000150:complications / Q000175:diagnosis* / Q000821:virology; D008297:Male; D008875:Middle Aged; D018357:Respiratory Syncytial Virus Infections / Q000150:complications / Q000175:diagnosis* / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D013147:Spirometry; D013183:Sputum / Q000821:virology*; D013997:Time Factors
D000914:Antibodies, Viral; D000956:Antigens, Viral