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Immunological diagnosis of early Pseudomonas aeruginosa lung infection in cystic fibrosis patients

Abstract number: R2403

Biffi A., Costantini D., Colombo C., Zazzeron L., Clarizia G., Garlaschi M.l., Cariani L.

Objectives: Serological methods to monitor Pa colonisation in patients with cystic fibrosis (CF) are advocated but the diagnostic value of a commercially available P. aeruginosa antibody test to detect early Pa colonisation has not been evaluated.

Methods: Colonisation of 235 CF patients (120 male) aged 10.5 years (range 1–30 years) was assessed by regular culture (every three months) of sputum or oropharyngeal secretions during four consecutive years (2003–2007). At the beginning of the study period all patients were negative for Pa.

Commercially available ELISA tests were performed to detect IgG and IgA against Pa lipopolysaccaride in sera once a year.

A subgroup of 46 patients (22 male) aged 10.5 years (range 2–24 years) showed culture conversion during the follow-up period and serology data of one year before (T-1) and one year after (T+1) the first infection, were compared.

Results: Serum antibody level (mean + SD) of immunoglobulin G (IgG) and immunoglobulin A (IgA) are showed in the table. IgG level at (T+1) was significantly higher when compared to (T-1).

In 13 patients (28%) at (T-1) the IgG levels were above the cut-off (6 U.I./ml), whereas the IgA levels were above the cut-off (8 U.I./ml) in 12 patients (26%).

At (T+1), 25 patients (54%) were positive for IgG antipseudomonas and 10 patients (22%) were positive for IgA.

Conclusions: Serology resulted in a higher number of positive patients than culture suggesting:

–higher diagnostic value of serology than culture,

–culture identification failures (because of lower bacteria densities in the airways in case of first infection),

–antibodies are markers of previous infection occurred several months or years before.

CF patients with positive serological tests and negative cultural tests might be monitored closely.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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