Fraction of exhaled nitric oxide in healthy elderly Tunisian subjects

• Current knowledge: Interpretation of FeNO data relies upon comparison of measured values with predicted ones available from published norms (e.g., fixed values, reference equations or normal values tables).
• In North-Africa, no local FeNO norms exist for elderly population and the use of norms derived from other populations is a questionable practice.
• What this paper contributes to our knowledge: The available published young and middle-aged adults' FeNO norms did not reliably predict FeNO in the present study population. Thus, a table of normal values according to age ranges was established.
• For elderly Tunisian, each measured FeNO value higher than 34 ppb will be considered as abnormal.
• In an additional healthy-validity-group, no subject with an abnormal FeNO was found. In another asthmatic-validity-group, 30% of subjects have an abnormal FeNO value.

IntroductionExhaled-fraction-of-nitric-oxide (FeNO) norms are absent in healthy elderly North-African subjects.Objectivesi) to identify FeNO influencing factors of elderly Tunisians older 50 years and more; ii) to assess the applicability of some published FeNO norms for elderly in local population; iii) to set-up FeNO norms and to prospectively evaluate their validity in two elderly validation-groups (healthy and asthmatic subjects).MethodsA convenience sample of healthy and asthmatic elderly Tunisians was recruited. Subjects responded to a medical questionnaire and then FeNO levels were measured by an online method (Medisoft, Sorinnes (Dinant), Belgium). Clinical, anthropometric and spirometric data were collected. Three groups of subjects were identified: group I (healthy-elderly; n = 100, 57 females); group II (healthy-validation; n = 17, 4 females) and group III (asthmatic-validation; n = 10, 9 females). ANOVA was performed to compare the three groups' data.ResultsNo significant factor, among those evaluated, influenced Tunisian elderly FeNO values. The available published FeNO norms did not reliably predict FeNO in Tunisian elderly population. The mean ± SD (minimum–maximum) of FeNO (ppb) for group I was 14 ± 6 (3–34). For Tunisian people, each elderly FeNO value higher than 34 ppb will be considered as abnormal. There was no statistical significant difference between FeNO (ppb) mean values of group I and groups II (15 ± 8) or III (18 ± 13). No subject of group II had a FeNO value higher than 34 ppb. Thirty percent of group III subjects had a FeNO value higher than 34 ppb.ConclusionIn practice, FeNO value of more than 34 ppb is considered abnormal in elderly Tunisian population.