Reproducibility of home spirometry in children with newly diagnosed asthma.

We evaluated the reproducibility of home spirometry in 110 children aged 5-10 years with newly diagnosed asthma according to the criteria proposed by the American Thoracic Society (level of reproducibility < or = 5%). Flow-volume spirometry was performed in the clinic. Spirometric values were then monitored twice daily at home for 24 days (mean), using a novel device, the Vitalograph(R) Data Storage Spirometer (Vitalograph, Ltd., Buckingham, UK). During this period, the mean (SD) compliance in performing the spirometric tests was 94% (7). In the whole study population, the mean (SD) percentage of reproducible spirometric measurements was 77% (17), although there was wide individual variation (range, 21-100%). In the 5-6-year age group (n = 51), the mean (SD) percentage of reproducible spirometric values was 72.8% (18.6), in the 7-8-year group (n = 38) 77.1% (13.8), and in the 9-10-year group (n = 21) 84. 5% (13.7) analysis of variance, P = 0.02). We conclude that most of the children aged 5-10 years could perform reproducible spirometric tests during home monitoring, although there was wide individual variation. Younger children were less likely to perform reproducible tests than older children. However, a considerable proportion of the measurements (23%) did not meet the criteria of acceptable reproducibility. In order to improve the quality of home monitoring, nonreproducible measurements should be excluded from the calculations. Copyright 2000 Wiley-Liss, Inc.