Ishizuka et al. Allergy, Asthma & Clinical Immunology 2011, 7:15 http://www.aacijournal.com/content/7/1/15 Page 5 of 8 of male than female students (p < 0.05) (B). Nocturnal attacks of cough were observed significantly more often in women than in men (p < 0.05). Among students with nocturnal attacks of cough, FENO was ≥ 38.0 ppb in a smaller percentage of female than male students (C). confirmed by challenge testing, not history or symp- toms. Information obtained from the questionnaire which only asks asthmatic symptoms and history of asthma is not enough to make diagnosis of asthma, because clinical suspicion of asthma should be con- firmed by objective measures of pulmonary function [20]. Strictly, current asthma symptoms on the ECRHS questionnaire are not equal to clinically current symp- toms because this questionnaire is designed to detect asthma symptoms over 1 year. Although we must also emphasize that the ROC curve was constructed only to classify subjects of this study and that it was not con- structed to help diagnose asthma, a previous study using the same offline method proposed that the optimal cut- off value of FENO was 38.0 ppb for detecting allergic airway inflammation in an adult population [10]. This cut-off value was equal to that we used in this study. In our survey, two symptoms, wheeze and a nocturnal attack of cough were most frequently reported. FENO was ≥ 38.0 ppb in more than 75% of subjects who had wheeze. In those students who had experienced wheez- ing, the percentage whose FENO was ≥ 38.0 ppb was significantly higher in men than in women. This sug- gests that wheeze as a subjective symptom correlates with the presence of chronic eosinophilic airway inflam- mation especially in men. In fact, wheeze is the most Figure 3 The percentage of students with wheezes or coughs whose FENO was ≥ 38.0 ppb. The percentage of students whose FENO was ≥ 38.0 ppb was higher in students with wheezes than in those with nocturnal attacks of cough (A). Among students with wheezes, FENO was ≥ 38.0 ppb in a significantly higher percentage Figure 4 The prevalence of asthma symptoms in students ranging in age from 18 to 24 years. Overall, 77 (13.2%) of 584 students experienced any asthmatic symptoms within the last year. One-year prevalence of asthma symptoms in university students ranging in age from 18 to 24 years was expected to be 13.2% at a maximum (A). FENO was over 38.0 ppb in 42 of the 77 students. The prevalence of asthma symptoms was estimated to be 7.2% by considering FENO levels (B).