title: Lung clearance index and moment ratios at different cut-off values in infant multiple-breath washout measurements.
abstract: Multiple-breath washout (MBW) is increasingly used for infant lung function testing. Current guidelines recommend calculating lung clearance index (LCI) and functional residual capacity (FRC) at 2.5% of normalized tracer gas concentration, without clear recommendation for moment ratios (MR). Whether the 2.5% cut-off has the highest discriminative power to detect ventilation inhomogeneity in infants with lung diseases is unknown.
  
  
  
  We used sulfur-hexafluoride MBW measurements from 32 infants with cystic fibrosis, 32 preterm infants, and 32 healthy controls at postmenstrual age of 41-54 weeks. We compared the discriminative power to detect pathological values above the upper limit of normal for 12 different cut-offs between 20% and 1.5% for first and second MR (MR1, MR2), LCI, and FRC.
  
  
  
  MR and LCI results changed significantly at different cut-offs. Mean MR2 in infants with cystic fibrosis increased from 2.4 to 7.2 units between 20% and 1.5% SF6. The ability of MR and LCI to discriminate between health and disease increased significantly with lower cut-offs. The 1.5% cut-off showed highest discriminative power: in infants with cystic fibrosis pathological MR2 values were found in 27 out of 89 (30%) and for LCI in 28/89 (32%). In preterm infants, pathological MR2 values were detected in 39 out of 73 (53%), and for LCI in 35/73 (48%). FRC remained stable throughout the washout.
  
  
  
  In infants, the diagnostic performance of MBW strongly depends on the point of analysis. The cut-off with the highest discriminative power to detect ventilation inhomogeneity in infants with cystic fibrosis and after preterm birth was at 1.5% tracer gas concentration. Pediatr Pulmonol. 2016;51:1373-1381. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Pediatrics, University of Basel Children's Hospital (UKBB), Spitalstrasse 33, Basel 4031, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Egger
authors.affiliation: Department of Pediatrics, University of Basel Children's Hospital (UKBB), Spitalstrasse 33, Basel 4031, Switzerland.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Jost
authors.affiliation: Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital Bern, University of Bern, Switzerland.
authors.forename: Pinelopi
authors.initials: P
authors.lastname: Anagnostopoulou
authors.affiliation: Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital Bern, University of Bern, Switzerland.
authors.forename: Sophie
authors.initials: S
authors.lastname: Yammine
authors.affiliation: Department of Pediatrics, University Children's Hospital Zurich, Zurich, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Singer
authors.affiliation: Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital Bern, University of Bern, Switzerland.
authors.forename: Carmen
authors.initials: C
authors.lastname: Casaulta
authors.affiliation: Department of Pediatrics, University of Basel Children's Hospital (UKBB), Spitalstrasse 33, Basel 4031, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Frey
authors.affiliation: Department of Pediatrics, University of Basel Children's Hospital (UKBB), Spitalstrasse 33, Basel 4031, Switzerland.|Division of Respiratory Medicine, Department of Pediatrics, University Children's Hospital Bern, University of Bern, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Latzin
mesh_terms: D001944:Breath Tests; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000503:physiopathology*; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D007223:Infant; D062071:Infant, Extremely Premature; D007234:Infant, Premature; D008168:Lung / Q000503:physiopathology*; D008171:Lung Diseases / Q000503:physiopathology; D008297:Male; D012123:Pulmonary Ventilation; D012129:Respiratory Function Tests / Q000379:methods*
keywords: infant lung function; lung clearance index; moment ratios; multiple-breath washout