The effect of challenge method on sensitivity and reactivity to adenosine 5'-monophosphate in subjects with suspected asthma.
BACKGROUND
The following two methods of inhalation challenge have been used to determine the airway responsiveness: the tidal-breathing method; and the dosimeter method. The objective of the study was to determine the influence of the challenge method on the response to adenosine 5'-monophosphate (AMP).


METHODS
This study measured airway responsiveness to AMP by dosimeter and tidal-breathing methods in 25 subjects with suspected asthma. The two AMP challenges were conducted in random order, on separate days, at the same time of day, at intervals of 1 to 5 days. Concentration-response curves were characterized by the provocative concentration of a substance causing a 20% fall in FEV1 (PC20) and slope.


RESULTS
The dosimeter PC20 values were significantly higher than the tidal-breathing PC20 values, with geometric mean (95% confidence interval [CI]) values of 50.35 mg/mL (95% CI, 19.50 to 129.72 mg/mL) and 28.97 mg/mL (95% CI, 11.99 to 69.98 mg/mL; p = 0.02), respectively. The mean difference in the PC20 values obtained with each method was 0.80 doubling concentrations (95% CI, 0.16 to 1.44 doubling concentrations). The mean values for the slope were 17.0%/log mg/mL (95% CI, 12.5 to 21.5 mg/mL) with the tidal breathing method and 13.8%/log mg/mL (95% CI, 9.0 to 18.7 mg/mL; p = 0.03) with the dosimeter.


CONCLUSIONS
The tidal-breathing method produces AMP PC20 values that are significantly lower than the dosimeter method and slope values that are significantly higher than the dosimeter method. These data suggest that the results obtained with each method of testing may not be comparable.
Prieto
Luis
L
Sección de Alergología, Hospital Universitario Dr. Peset, C/ Gaspar Aguilar 90, 46017 Valencia, Spain. prieto_jes@gva.es
Reig
Isabel
I
Rojas
Rocio
R
Ferrer
Anna
A
Domenech
Juan
J
D000249:Adenosine Monophosphate / Q000494:pharmacology*; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000379:methods*; D018592:Cross-Over Studies; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D036501:Metered Dose Inhalers; D008875:Middle Aged; D011897:Random Allocation; D012680:Sensitivity and Specificity; D013990:Tidal Volume / Q000502:physiology
D000249:Adenosine Monophosphate