Prevalence of bronchial reactivity to inhaled methacholine in New Zealand children.

Abstract

The prevalence of bronchial hyperreactivity to inhaled methacholine and of a clinical history of symptoms of asthma was determined in a birth cohort of 9 year old New Zealand children. A history of current or previous recurrent wheezing was obtained in 220 of 815 children. Of 800 who had spirometric tests, 27 (3.4%) had resting airflow obstruction (FEV,/FVC < 75%). Methacholine challenge was undertaken without problem in 766 children, the abbreviated protocol being based on five breaths and four concentrations. A fall in FEV, of more than 20% was observed in 176 children (23% of challenges, 22% of the full cohort) after inhalation of methacholine in concentrations of up to 25 mg/ml. The prevalence of bronchial reactivity in children with symptoms was related to the frequency of wheezing episodes in the last year, and the degree of reactivity to the interval since the last episode. Sixty four children (8.0%) with no history of wheeze or recurrent dry cough were, however, also responsive to methacholine 25 mg/ml or less, while 35% of children with current or previous wheezing did not respond to any dose of methacholine. Bronchial challenge by methacholine inhalation was not sufficiently sensitive or specific to be useful as a major criterion for the diagnosis of asthma in epidemiological studies. The occurrence of airway reactivity in children without symptoms of asthma, however, raises the possibility that adult onset asthma and the development of airways obstruction in some subjects with chronic bronchitis could have origins in childhood.Asthma, although one of the most common diseases of childhood, is underdiagnosed and undertreated.'`3 The prevalence of childhood asthma is difficult to determine with certainty; estimates in New Zealand have ranged from 5% to 25%.' 4 -7 We have previously reported a high prevalence of a history of wheezing in 7 year old children.' Our results were in keeping with Australian findings that 11-12% of children have clinically important wheezing in the first 7-10 years of life, and that a further 20% may have mild or trivial wheezing not labelled as asthma.8 9 Some of the variation in reported prevalence is attributable to differing interpretations of a history of wheezing, and the demonstration of bronchial reacAddress for reprint requests:

Methacholine inhalation challenge: a shorter, cheaper and safe approach

“…In the protocol used by Sears et al [15] in an epidemiological setting, the concentration of MCh was increased in ten-fold steps. Simulating the Sears et al [15] protocol on the records of patients from the present study, rather than random population, it was calculated that 179 of 449 patients (40%) would have reacted with a severe bronchoconstriction (i.e. DFEV1 >40%).…”

Sex Differences in Factors Associated with Childhood- and Adolescent-Onset Wheeze

“…Research Study (7,21,24,(28)(29)(30)(31)(32)(33)(34) were born April 1972 through March 1973. A population-representative birth cohort of 1,037 children was assessed at age 3.…”

Non specific bronchial hyperreactivity in infants

“…Com relação à medida da HRB pelos TBP com metacolina, estudos recentes têm sugerido que ambas podem ser melhoradas se forem realizadas medições de modo seriado ao longo do tempo 10,28,30,36 . Em estudos evolutivos, têm-se observado graus mais acentuados de HRB entre crianças, muitas vezes precedendo às vezes até em anos o aparecimento dos sintomas 32,[36][37][38][39][40] .…”