A comparison of nested polymerase chain reaction and immunofluorescence for the diagnosis of respiratory infections in children with bronchiolitis, and the implications for a cohorting strategy

Cohorting bronchiolitis patients infected with respiratory syncytial virus (RSV) and/or influenza viruses is paramount in preventing cross-infection o f these viruses in hospital. Nested polymerase chain reaction (nPCR) was co mpared with immunofluorescence (IF) for the detection of RSV subtypes A and B in children with suspected bronchiolitis. Co-infection with influenza A( H3N2), Chlamydia spp. and picornavirus/rhinovirus was also investigated usi ng molecular techniques. A total of 50 nasopharyngeal secretions collected from babies admitted with bronchiolitis in the month of January 2000, comprising IF RSV positive (N= 27) and RSV negative (N= 23) specimens, were tested for both RSV subtypes, influenza A(H3N2), Chlamydia spp. and picornavirus/rhinovirus by nPCR. Nested PCR detected 28 specimens positive for RSV (RSV A = 20, RSV B = 8), which was two more than detected by IF Influenza A(H3N2) was detected in th ree specimens, Chlamydia trachomatis in one, and picornavirus in 11, of whi ch nine were confirmed to be rhinovirus by nPCR. Dual infection was detecte d in five cases using nPCR. Nested PCR proved useful in detecting RSV and influenza A(H3N2) infections missed by IF, and also other respiratory tract pathogens not routinely inve stigated. The clinical implications and risk of cross-infection with potent ially virulent viruses due to inaccurate results from insensitive technique s, highlights the need for molecular assays such as nPCR to be employed as a routine method of investigation, provided as part of the laboratory servi ce. Cohorting of patients with clinical bronchiolitis should continue, whil st awaiting laboratory confirmation. (C) 2001 The Hospital Infection Societ y.