Inhaled mannitol identifies methacholine responsive children with current asthma

Bronchial provocation testing using mannitol can identify currently active asthma in adults (AJRCCM 1998;158:1120-26). AIM: To investigate responses to mannitol in 25 physician diagnosed, currently treated asthmatic (16M, 9F) & 10 non-asthmatic (5M, 5F) children (6-13yrs). METHOD: Children performed a methacholine challenge via the Cockcroft method (Clin Allergy 1977;7:235-243) followed by a mannitol challenge (AJRCCM 1997;156:758-765) on separate days. Dose of mannitol and concentration of methacholine to provoke a 15% (PD.s) and 20% (PCzo) fall in FEV1 respectively were compared. RESULTS: Twenty-one asthmatics were identified with mannitol. Three children regularly taking steroids with borderline methacholine responsiveness (PC20 4-16mg/ml) did not respond to mannitol. One could not complete the mannitol challenge due to cough on inhalation. There was a good association between PD 15 vs PC 20 (r P = 0.75, p<0.001). The Geomean (95%CI) PD 15 was 40 mg (20,81) compared with PC 20 of 0.6 mg/ml (0.35-1.02) (n=21). Mannitol challenges were significantly faster to perform than methacholine (median (range) 14min (5-32) vs 29 min (19-49), p<0.001). Responses to mannitol were repeatable with PDis for the 1st challenge 29 mg (Cl:17,50) & for the 2nd 33 mg (Cl:20,55) p=0.44 (n=9). Time to recover spontaneously & with bronchodilator to baseline FEV. was similar for both challenges (ANOVA p=ns). There were no significant falls in SaOz. There were no significant falls in FEVi in non-asthmatic children (mean (SD) 3.1% (2.9)). CONCLUSION: Mannitol is a fast, repeatable and safe challenge that can be used to identify children with current asthma.