Histamine challenges discriminate between symptomatic and asymptomatic children

The aims of this study were to investigate a threshold value for branchial responsiveness in children aged 7 yrs, which discriminates between symptoma tic and asymptomatic children, and to identify determinants of this respons iveness. Titrated branchial histamine challenges using the reservoir method were per formed in 645 children aged 7 yrs, from the birth cohort Multicentre Allerg y Study (MAS). When defining a reference population of healthy children within the MAS coh ort? the 95th percentile of the provocative concentration causing a 20% fai l in forced expired volume in one second PC20 among these asymptomatic stud y subjects amounted to 0.60 mg.mL(-1) This resulted in a specificity of 93. 0% and a sensitivity of 45.9%, for discriminating between "current wheezers " and "non-current wheezers". Determinants of airway responsiveness at this age were pulmonary function, sensitization to indoor allergens, total immu noglobulin E and current wheeze, The results indicate that a very low cut-off provocative concentration caus ing a 20% fall in forced expired volume in one second (<1.0 mg.mL(-1)) defi nes airway hyperresponsiveness in children aged 7 yrs using the reservoir m ethod. Provocation protocols far histamine challenges in this age group sho uld therefore start with concentrations markedly below 1.0 mg.mL(-1).