Exhaled breath condensate pH in adult Croatian population without respiratory disorders: how healthy a population should be to provide normative data?

The aim of this study was to obtain preliminary exhaled breath condensate (EBC) pH values for healthy adult Croatian subjects, and to evaluate criteria for defining respiratory health of population providing normal EBC pH values in epidemiologic studies. In 109 adults without a history of lower airway symptoms (AS), four groups were described by narrowing the definition of "health" down to 1) without lower AS; 2) without lower and upper AS; 3) without AS, with normal FEV(1) and bronchial normoreactivity; 4) without AS, with normal FEV(1), bronchial normoreactivity, normal total IgE, and with negative skin prick test. Median EBC pH values did not differ between the groups (7.72, 7.73, 7.73, 7.73), but as health criteria got stricter, we observed a slight, nonsignificant increase in minimal pH values (6.95, 7.10, 7.20, 7.37). Median EBC pH values with interquartile range in the total sample (7.72; 7.63 to 7.76) were within the range previously reported by other authors. They did not differ regarding sex, smoking habit and atopic status, and were not associated with age, FEV(1) or total IgE. The non-significant trend in EBC pH observed with stricter criteria of respiratory health and atopic status indicates the need for further research on criteria for defining healthy population in a larger sample.