PEAK FLOW VARIATION IN CHILDHOOD ASTHMA - A 3-YEAR ANALYSIS

Measuring peak expiratory flow (PEF) variation has been suggested as a indicator of asthma disease severity and also of nonspecific bronchia l hyperreactivity. To test these assumptions, we examined the relation ships between PEF variation, methacholine reactivity, symptom scores, and medication requirements in 74 children with tightly controlled all ergic asthma. The level of mean diurnal variation (MDV) for the group was 7.1%, which is generally regarded as normal. We found statisticall y significant correlations between MDV and both methacholine reactivit y (r = 0.43, p = 0.0001) and symptom scores (r = 0.28, p = 0.016). The se asthma variables were analyzed longitudinally in 33 children who we re followed up at 6-month intervals for at least 36 months. Visit-to-v isit changes in MDV were generally not reflective of changes in other variables. However, group levels of MDV gradually decreased over time, especially in children with initial MDV of more than 8%. This reducti on in group MDV coincided with similar reductions in group medication requirements and methacholine reactivity. We conclude that children wi th moderately severe asthma that is tightly controlled may have normal levels of PEF variation. The correlation between PEF variation and ot her asthma variables is statistically significant but too weak to be u seful in the treatment of individual patients. In contrast, measuremen t of MDV may be a useful indicator of disease severity in group studie s of asthma.