Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients

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Abstract

Background: Patients were defined each successive month as either ‘chronic’ when more than 50% of the preceding 12 months were PA culture positive, ‘intermittent’ when ≤50% of the preceding 12 months were PA culture positive, ‘free of PA’, with no growth of PA for the previous 12 months, having previously been PA culture positive, or ‘never infected’, when PA had never been cultured. Methods: Cross-sectional analysis of 146 children attending the Leeds Regional Cystic Fibrosis Centre was performed to assess relationship between the new definition and clinical scores and investigations. The response variable was regressed on age and sex and the residuals analysed using the Kruskal–Wallis test. Results: The ‘chronic’ group (18% of patients) had significantly worse Shwachman–Kulczycki (SK) and Northern chest X-ray scores, and % predicted FEV1 values than the ‘free’ (28%) or ‘never’ (20%) categories (P<0.004). The ‘intermittent’ group (34%) had a significantly higher SK score than the ‘chronic’ group (P<0.0001), and a significantly lower % predicted FEV1 value than the ‘free’ or ‘never’ groups (P<0.0003). ‘Chronic’ patients were significantly associated with a positive, and ‘never’ patients with a negative, PA antibody result (P<0.001). Conclusions: The validity and importance of identifying these four subgroups is demonstrated. Previous definitions may over-estimate the prevalence of chronic infection.

Keywords

Intermittent
Pseudomonas aeruginosa infection
Evaluation study
Classification

Abbreviations

PA: Pseudomonas aeruginosa
CF: Cystic fibrosis
FEV1: Forced expiratory volume in one second
SK: Shwachman–Kulczycki

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