Table 4

 Prognostic values of serum antibody determination: results from evaluation over the 2 years following the initial determination of antibody titres

Free (N = 66)Intermittent (N = 24)
PPV, positive predictive value; NPV, negative predictive value.
Predictive values were calculated on the basis of the prevalence of P aeruginosa after 2 years based on the serum antibody results (15/66 (22.7%) in the P aeruginosa free group and 13/24 (54.2%) in the intermittently infected group) to determine the probability for a CF patient to shift his or her P aeruginosa status depending on the antibody titre.
PPV % (95% CI)33.3 (0.8 to 90.6)83.0 (51.6 to 97.9)
    n/N1/310/12
NPV % (95% CI)77.8 (76.5 to 94.4)58.0 (27.7 to 84.8)
    n/N49/637/12