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Introduction. In the exercise challenge test (ECT), a drop in forced expiratory volume in the first second (FEV1) of between 10 and 15% is the determinant variable for a diagnosis of exercise-induced bronchospasm. Hypothesis. The use of FEV1 plus mean forced expiratory flow between 25% and 75% of the forced vital capacity (FEF25-75%) may increase the sensitivity of the ECT in asthmatic children. Specific objective. To compare FEV1 and FEF25-75% changes in a group of asthmatic and healthy children. Methodology. This was a cross-sectional study. Asthmatics were categorized by their severity (GINA) and after 1 month without controller therapy, an ECT was done under standard protocol. As well, a questionnaire about rhinitis and asthma was conducted with the entire population. ROC curves were used for analysis. Results. A total of 147 children (34 healthy and 113 asthmatics, 18 and 58 males, respectively) were evaluated. Divided into healthy children and intermittent, mild and moderate persistent asthmatics, they had similar average ages (9.4, 9.48, 8.97, and 11.2 years, respectively). Using a 15% fall in FEV1, we obtained 29% sensitivity and 100% specificity. However, when we used a 10% fall in FEV1, sensitivity was 47% and specificity was 97%. Adding a 28% fall in FEF25-75%, sensitivity was 52% and specificity was 94%. Conclusion. This study suggests that test sensitivity can increase by using a lower FEV1 cut-off (10%) and adding a 28% fall in FEF25-75%. [ABSTRACT FROM AUTHOR]