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P255 Reproducibility of lung clearance index (LCI) in clinically stable adults with mild cystic fibrosis (CF)
  1. AR Horsley1,
  2. A Shawcross1,
  3. M Oladapo2,
  4. A Maitra2,
  5. S Cunningham3,
  6. AM Jones4,
  7. J Smith1,
  8. F Gilchrist5
  1. 1University of Manchester, Manchester, UK
  2. 2Royal Manchester Children’s Hospital, Manchester, UK
  3. 3Royal Hospital for Sick Children, Edinburgh, UK
  4. 4Manchester Adult Cystic Fibrosis Centre, Manchester, UK
  5. 5Royal Stoke University Hospital, Stoke, UK


Background In order for lung clearance index (LCI) to be a clinically useful measurement, a better understanding is required of short-term variability. LCI-SEARCH is a longitudinal study in children and adults with CF, with LCI measured at each clinical review using a portable closed-circuit wash-in system ( Here we report initial LCI repeatability from the adult cohort.

Methods LCI measurements were performed in triplicate using a closed-circuit wash-in method (Horsley et al. ERJ open). The most recent paired LCI measurements were included providing they were within 6 months of each other, the patient was deemed clinically stable by a physician and the patient scored <2 on a 4 point respiratory symptom score. Repeatability was assessed by Bland-Altman analysis.

Results Of 40 CF adults, paired data were available on 21 (7 subjects had completed only 1 assessment, 1 withdrawn, 11 clinically unstable). These 21 subjects (14 male) completed a median of 5 LCI measurements each (range 2–11), a median of 84 (range 42–189) days apart. Mean age was 28 yrs, mean FEV1 82% predicted, 11 pancreatic sufficient, 11 had never had pseudomonas infection.

Mean (SD) LCI at visit 1 was 8.68 (2.96) vs 8.73 (2.81) at visit 2 (p = ns). Median coefficient of variation for LCI was 3.9% (visit 1) and 4.2% (visit 2). Mean change in LCI between visits was 0.05 (1% of baseline LCI). 95% limits of agreement (LOA) were −1.1 (−13.7)% to 1.0 (11.6)% of baseline LCI. In this very mild cohort, 7 patients had normal LCI (<7); exclusion of these did not substantially alter LOA (−13.9 to 13.1%). There was greater variability in FRC: mean bias −1.5% of baseline (LOA 30 to −33%).

Conclusions Even in this very mild cohort of CF adults, patients are frequently unwell or more symptomatic at routine review. Within-visit repeatability was good, and similar to previous reports. When clinically stable, LCI variability over a period of up to 6months was approximately ± 10%. Addition of more adult as well as paediatric data to this assessment will widen the applicability of these confidence intervals.

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