Assessing pulmonary function in 3-year-old children using respiratory oscillometry: a validation study in rural Guatemala.

BACKGROUND: Respiratory oscillometry can inform early-life lung function, but evidence supporting its use in Guatemala is limited. We assessed the validity and reliability of respiratory oscillometry in 3-year-old Guatemalan children and whether these improve with quality control (QC). METHODS: During home visits, we measured respiratory oscillometry resistance (R) and reactance (X) at 7 Hz (R7 and X7), the frequency dependence of resistance (R7-R19) and the area of reactance (AX) in 666 children participating in the Household Air Pollution Intervention Network trial. Standard measurement QC removed artefacts using commercial software and selected the first three measurements with an R7 coefficient of variation of ≤15%. Alternative investigators' methods varied in QC procedures. We evaluated validity as the proportion of variability in tests predicted by a child's height (R2) and, in a subset of 50 children, as agreement with test results after manual QC by a paediatric pulmonologist. Reliability was assessed by the intraclass correlation coefficient (ICC) of repeated tests. RESULTS: We collected oscillometry results from 537 children. Height explained 5-15% of the variability in R7, X7 and AX, but none in R7-R19. The correlation between standard and manually cleaned tests ranged from 0.66 to 0.97, depending on the parameter. Of the first tests, between-day ICCs using the standard method for R7, R7-R19, X7 and AX were 0.68, 0.45, 0.60 and 0.71, respectively, and the best between-day ICCs using an alternative method were 0.75, 0.57, 0.69 and 0.74, respectively. DISCUSSION: We demonstrated good validity and reliability of respiratory oscillometry measurements collected at home from preschool-aged Guatemalan children. Investigators' automated QC methodology performed equally to or better than standard methodology.