ADENOSINE, METHACHOLINE, AND EXERCISE CHALLENGES IN CHILDREN WITH ASTHMA OR PEDIATRIC CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background - Bronchial hyperreactivity to methacholine is present in c hildren with asthma and other types of paediatric chronic obstructive pulmonary disease (COPD), while hyperreactivity to exercise is more sp ecific for asthma. Adenosine 5'-monophosphate (AMP) is a potent bronch oconstrictor and, like exercise, may provoke asthma by activating mast cells. This study investigated the suitability of AMP as a specific c hallenge for asthma in children. Methods - Bronchial provocation chall enges with methacholine and AMP were performed in a double blind fashi on using tidal breathing in 51 children with asthma, 21 with paediatri c COPD of various types, and in 19 control children. Each subject also underwent a standardised exercise challenge after inhalation challeng es were completed. Sensitivity and specificity curves were constructed and the intersection point of sensitivity and specificity for each ty pe of challenge was determined. Results - When the asthmatic patients were;compared with the children with COPD, the intersection points for AMP, exercise and methacholine were 90%, 85%, and 50%, respectively. When compared with the controls the same intersection points were 98%, 84%, and 92%, and when children with paediatric COPD were compared wi th controls they were 55%, 50%, and 82%. Conclusions - Methacholine di stinguishes both asthma and paediatric COPD from controls with a sensi tivity of 82-92%, but does not distinguish between asthma and paediatr ic COPD; exercise and AMP distinguish asthma from controls with a sens itivity and specificity of 84-98% but they also distinguish asthma fro m paediatric COPD with a sensitivity and specificity of 85-90%. AMP in halation is a practical aid for diagnosing asthma and distinguishing i t from COPD in children of all ages.