Abstract

Increased bronchial hyperresponsiveness (BHR) is an essential feature of asthma. In clinical studies methacholine challenge is generally used to measure BHR. However, adenosine monophosphate (AMP) - an indirect stimulus- has been suggested to be a better marker for airway inflammation since it is more closely related with asthmatic inflammatory processes. In order to assess the responsiveness of asthmatic airways to AMP and compare its diagnostic value with respect to methacholine challenge we performed methacholine and AMP bronchoprovocation tests in 22 asthmatics (19 women, 3 men; median age 34.77±15.38 yrs), 10 smoker and 11 nonsmoker healthy volunteers. For each type of challenge, sensitivity and specificity curves were constructed. Intersection points of these curves were used as cut-off points in differentiating asthmatics from controls. The median PC20 values were as follows: asthmatics 3.39±5.02 mg/mL, smokers 39.17±22.23 mg/mL, nonsmokers 57.66±15.28 mg/mL for methacholine; asthmatics 44.73±85.30 mg/mL, smokers and nonsmokers 800±0 mg/ml for AMP. Methacholine distinguished asthmatics from smokers and nonsmokers with a sensitivity and specificity of 94%-96% at 6.8 mg/ml and 13 mg/mL concentrations, respectively. AMP distinguished asthmatics from both controls at 100 mg/mL concentration with 100% sensitivity and specificity. In our study population AMP bronchoprovocation was found to be a more appropriate screening test and inflammatory marker differentiating asthma from healthy controls.