Introduction LCI obtained from multiple breath washout (MBW) is a sensitive measure of ventilation inhomogeneity in CF. Persistent colonisation with P. aeruginosa is associated with a decline in LCI in children (Kraemer et al. 2006). Further research is required to investigate the relationship between airways infection and LCI in adults.
Objective To investigate the sensitivity of LCI to P. aeruginosa in adults and children compared with FEV1%pred and FEF25–75%pred.
Methods Stable CF patients from adult & paediatric Northern Ireland CF centres were recruited. LCI was derived from MBW, using 0.2% SF6 and a modified InnocorTMdevice. P. aeruginosa status was determined from routine diagnostic culture of a sputum sample or deep throat swab. Patients categorised as having P. aeruginosa infection met the criteria of chronic infection as defined by the Leeds criteria (Lee et al. 2003).
Analysis Receiver-operator characteristic (ROC) curves and area under the receiver operating curves (AUCROC) indicate the level of sensitivity and specificity where 1.0 = perfect discrimination considering sensitivity and specificity.
Results Sixty-seven adults were recruited (39M), median (IQR) age 27 (16) years. Mean (SD) FEV1%pred 71.8 (20.3), median (IQR) FEF25–75%pred 40.0 (46.7) and mean (SD) LCI 10.3 (3.0) lung volume turnovers. 49% had P. aeruginosa infection.
Forty-three children were recruited (24M), mean (SD) age 11.7 (3.4) years. Mean (SD) FEV1%pred 85.2 (16.6), mean (SD) FEF25–75%pred 66.0 (27.6) and mean (SD) LCI was 7.8 (1.8) lung volume turnovers. 16% had P. aeruginosa infection
Compared to FEV1%pred and FEF25–75%pred, LCI had the greatest sensitivity and specificity to discriminate between CF patients with and without P. aeruginosa in both adults and children. Adult AUCROC (SE) for LCI = 0.82 (0.05), p < 0.0001, compared with FEV1%pred = 0.66 (0.07), p = 0.021 and FEF25–75%pred = 0.64 (0.07), p = 0.044 (Figure 1). Child AUCROC (SE) for LCI = 0.85 (0.10), p = 0.004, compared with FEV1%pred = 0.80 (0.12), p = 0.014 and FEF25–75%pred = 0.67 (0.13), p = 0.152.
Conclusion LCI is more sensitive and specific to the presence of P. aeruginosa airways infection across the age groups in CF compared with spirometry.
This project was funded by a US-Ireland Project Partnership Grant.
References Kraemer, R et al 2006, Respiratory
Research. Lee, T W R et al 2003, Journal of Cystic Fibrosis.
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