Diagnostische und prognostische Relevanz der Pseudomonas aeruginosa Antikörperbestimmung bei Patienten mit Cystischer Fibrose

BACKGROUND: Eradication of Pseudomonas aeruginosa in patients with
cystic fibrosis (CF) is possible if initiated early in the course
of colonisation. To detect P aeruginosa as early as possible is
therefore a major goal. This study was undertaken to validate a
commercialised test for the detection of serum Pseudomonas
antibodies in patients with CF. METHODS: A representative cross
sectional analysis of serum antibodies against three Pseudomonas
antigens (alkaline protease, elastase, and exotoxin A) was
performed in 183 patients with CF of mean age 16.7 years and FEV1
85.9% predicted. The results were correlated with microbiological
results from the previous 2 years to calculate sensitivity,
specificity, positive and negative predictive values. The following
2 years were assessed to determine prognostic predictive values.
RESULTS: A combination of all three tested antibodies yielded the
best results with a sensitivity of 86%, specificity of 96%, and a
positive predictive value of 97%. These values were higher if only
patients in whom sputum cultures were available were considered (n
= 76, sensitivity 95%, specificity 100%, positive predictive value
100%). The prognostic positive predictive value was high in
intermittently infected patients (83%) but low in patients free of
infection (33%), whereas the prognostic negative predictive value
was high in patients free of infection (78%) and low in
intermittently infected patients (58%). CONCLUSIONS: Regular
determination of serum antibodies may be useful in CF patients with
negative or intermittent but not with positive P aeruginosa status.
A rise in antibody titres indicates probable infection and
eradication treatment may be initiated even in the absence of
microbiological detection of P aeruginosa.