Mannitol and exercise challenge tests in asthmatic children

Bronchial hyperresponsiveness (BHR), a characteristic feature of asthma, can be assessed through standardized bronchial provocation tests (BPT). Exercise as a BPT is used in diagnosing and monitoring exercise induced bronchoconstriction (EIB). Recently a novel osmotic BPT has been developed, using dry powder mannitol. The aim of this study was to investigate the clinical utility of the mannitol challenge to identify asthmatic children with EIB.

Thirty-three clinically stable children, aged 9-18 years, with a history of EIB, performed both mannitol and exercise provocation challenges. Data were composed of a cross tabulation comparing the reaction on exercise provocation challenge to mannitol challenge. Correlations between post-exercise fall in FEV1 and response-dose ratio (RDR) and PD1) of mannitol were calculated.

Twenty-five children completed both tests. Pearson's correlation between log-transformed RDR for mannitol and post-exercise fall in FEV1 was r(p) = 0.666 (P < 0.001). There was no significant relationship between the log PD1) of mannitol and post-exercise fall in FEV1. Children on long acting bronchodilator agents (LABA) were significantly (P < 0.05) more likely to have a positive response on the mannitol challenge. Positive and negative predictive values of the mannitol challenge for EIB were 69% and 91%.

Mannitol challenge appears to be a suitable alternative for an exercise provocation test to assess EIB in asthmatic children. Given the negative predictive value of 91%, it is especially useful to exclude EIB.