Abstract
Background
Little is known how subject characteristics affect the airway responsiveness to mannitol, what is the upper limit of a normal response, and what is the reproducibility of the response among healthy subjects.
Methods
Mannitol testing was performed in 125 healthy, nonsmoking subjects with an age range of 18–82 years and an almost equal male-to-female ratio. 25 of them repeated the test. The airway response to mannitol was expressed as the final percentage fall in forced expiratory volume in 1 s (FEV1) after the final cumulative dose of mannitol (FFALL) and as response-to-dose ratio (RDR), calculated as FFALL divided by the final cumulative dose of mannitol. The upper limits of the normal response were calculated as mean+1.65×sd.
Results
Neither age, gender, height, body mass index, atopy, nor baseline FEV1 affected the responses statistically significantly. The mean±sd FFALL was 5.29±4.90% with an upper limit of 13.4%. The mean±sd RDR was 0.78±0.71% per 100 mg with an upper limit of 1.96% per 100 mg. In the repeated tests, the intraclass correlation coefficients were 0.46 and 0.35, respectively.
Conclusion
The subject characteristics do not have a significant effect on the airway responsiveness to mannitol. Therefore, the same upper limits of a normal response can be used in all adult nonsmoking subjects. Among healthy subjects with very mild airway responsiveness to mannitol, FFALL and RDR are poorly reproducible.
