Methacholine, cold air and exercise challenge tests in the diagnosis of bronchial responsiveness at school age: A follow-up study from birth to school age

The aim of the present study was to compare three bronchial challenge tests for assessing bronchial hyperresponsiveness (BHR) in twin pairs followed up from birth to school age. We studied three different bronchial challenge tests (methacholine inhalation challenge, cold air inhalation challenge and exercise-bronchodilation tests) at school age in 29 children born at or before 38 weeks gestation (median 35 weeks gestation) from multiple pregnancies. The children had been followed up from birth and were examined at the age of 7-15 years (median age 10 years). Bronchial hyperresponsiveness was found in 28-34% of children when these tests were analyzed separately. Eight children (28%) were exercise responders; two of them and three additional children were bronchodilator responders. Thus, 11 children (38%) had a pathologic result in the exercise-bronchodilation test. Ten children (34%) responded to cold air and nine children (31%) responded to methacholine inhalation. At least one test was pathologic in 18 children (62%), but only two children (7%) responded in all three challenges. A positive result in the exercise-bronchodilation test was associated with cold air reactivity, but not with methacholine reactivity. The exercise and cold air tests detected predominantly the same children. No differences were found in bronchial challenge test results between children who, at birth, were appropriately grown and those who had intrauterine growth retardation. Bronchial hyperresponsiveness was common (up to 62%) at school age in children born as moderately preterm. The outdoor exercise-bronchodilation test found 61% of all BHR cases. Bronchial hyperresponsiveness was not associated with intrauterine growth status. The most sensitive test was the cold air inhalation challenge and a good agreement was seen between this test and the exercise challenge outdoors.