Diagnostic value of serological tests against Pseudomonas aeruginosa in a large cystic fibrosis population

Thorax. 2006 Aug;61(8):689-93. doi: 10.1136/thx.2005.054726. Epub 2006 Apr 6.

Abstract

Background: Serological methods to monitor Pseudomonas aeruginosa colonisation in patients with cystic fibrosis (CF) are advocated but the diagnostic value of a commercially available P aeruginosa antibody test to detect early and chronic P aeruginosa colonisation in a non-research setting has not been assessed.

Methods: Colonisation with P aeruginosa was estimated by regular culture of sputum or oropharyngeal swabs during three consecutive years in 220 patients with CF aged 0-65 years. Commercially available ELISA tests with three P aeruginosa antigens (elastase, exotoxin A, alkaline protease) were performed at the end of the study period. In a subgroup of 57 patients (aged 4-14 years) serological tests were performed annually.

Results: Using culture as the reference standard, the ELISA tests using the advised cut off values had a sensitivity of 79% and a specificity of 89% for chronic colonisation. Receiver-operator characteristic curves were created to optimise cut off values. Applying these new cut off values resulted in a sensitivity of 96% and a specificity of 79%. All three individual serological tests discriminated well between the absence and presence of chronic P aeruginosa colonisation. The sensitivity of the individual antibody test was 87% for elastase, 79% for exotoxin A, and 76% for alkaline protease. First colonisation was preceded by positive serological results in only five of 13 patients (38%).

Conclusion: In patients with CF, serological tests using specific antigens are sensitive for diagnosing chronic P aeruginosa colonisation. However, the failure of serological tests to detect early colonisation in young patients emphasises the need for continued reliance on cultures.

Publication types

  • Evaluation Study

MeSH terms

  • Adult
  • Aged
  • Antibodies, Bacterial / blood*
  • Antigens, Bacterial
  • Cystic Fibrosis / microbiology*
  • Enzyme-Linked Immunosorbent Assay / standards
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pseudomonas Infections / diagnosis*
  • Pseudomonas aeruginosa / immunology*
  • ROC Curve
  • Reference Standards
  • Sensitivity and Specificity

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial