Exercise challenge test protocol under scrutiny
MedWire News: Results from the exercise challenge test (ECT) to assess pediatric asthma must be interpreted in light of the child’s age, Israeli researchers believe.
Their study showed that the time to maximal bronchoconstriction post-ECT is age-dependent, implying that the schedule of post-exercise spirometry “should be cautiously trimmed.”
Daphna Vilozni (Sheba Medical Center, Tel-HaShomer, Ramat Gan) and colleagues studied the relation between age and time to maximal bronchoconstriction (known as “Nadir-t”) following the ECT.
The standard ECT protocol requires spirometry to be performed at 3, 5, 10, 15, 20, and 30 minutes after cessation of exercise, they explain. This is time-consuming, however, so in practice fewer measurements are generally used.
For the present study, Vilozni et al evaluated data on 131 children aged 3–18 years who underwent the ECT in line with standard protocols. Baseline FEV1 values were 90.5% of predicted, the FEV1 nadir was 23.6% below baseline, and the Nadir-t was reached at 5.1 minutes, on average, after stopping exercise.
There was a significant positive correlation between children’s age and Nadir-t, the researchers report in the journal Respiratory Medicine. This remained significant irrespective of whether a positive ECT was defined as a 10% or a 15% fall from baseline FEV1.
Children under 10 years of age reached Nadir-t at 3.4 minutes post-exercise, on average, while older children reached Nadir-t at 6.6 minutes, on average. This difference was statistically significant.
Vilozni et al say that their results demonstrate that the time to maximal post-exercise bronchoconstriction is age-dependent and is reached more rapidly by younger children.
“The protocol of post-exercise FEV1 is of major importance,” the authors remark.
“Additional earlier measurements, particularly in the younger age groups, may detect patients with positive ECT who would have been missed otherwise.”
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By Joanna Lyford