Observer variability of lung function measurements in 2-6-yr-old children

The aim of this study was to assess the within-observer and between observe r variability of lung function measurements in children aged 2-6 yrs. Two observers examined 22 asthmatic children independently according to a p redefined protocol. Each observer obtained duplicate measurements of respir atory resistance by the interrupter technique (Rint), respiratory resistanc e (Rrs,5) and reactance (Xrs,5) at 5 Hz by the impulse oscillation techniqu e and the specific airway resistance (sRaw) by whole body plethysmography. The within-subject so (sDw) was not significantly different in the two obse rvers. The ratio sDw between observers/mean sow within observers was 0.94, 1.25, 1.35 and 2.86 for Xrs,5, Rrs,5, sRaw and Rint, respectively, indicati ng greater between-observer variability of the latter. The systematic diffe rence between observers assessed by the difference between observer means ( expressed as a percentage of their mean value) was 11, 7, 6 and 2% for Xrs, 5, sRaw, Rrs,5 and Rint, respectively. These differences were statistically significant, except that for Rint. In conclusion, specific airway resistance, impulse oscillation technique an d respiratory resistance assessed by the interrupter technique measurements in young children are subject to influence by the observer, and the random variability between observers appears to be particularly great for respira tory resistance assessed by the interrupter technique. The authors suggest that the between-observer variability should be investigated when evaluatin g novel methods for testing lung function.