Fraction of exhaled nitric oxide (FeNO ) norms in healthy North African children 5-16 years old

Defining the normal range of fractional exhaled nitric oxide in children: one size does not fit all

Background

The normal range of fractional exhaled nitric oxide (F ENO) is influenced by demographic factors. However, single, fixed cut-off values are used for clinical interpretation in children despite rapid growth. We aimed to define the normal range of F ENO during childhood and evaluate its utility in a diagnostic setting.

Method

F ENO percentile charts were developed using data from nonasthmatic children in a population-based birth cohort (Manchester Asthma and Allergy Study). Children were skin prick tested, F ENO measured at the ages of 8, 11, 13-16 and 18 years and clinical information collected. This chart was externally validated in the Study of Eczema and Asthma to Observe the Influence of Nutrition (SEATON) cohort before being prospectively tested in symptomatic, treatment-naïve patients with suspected asthma in a diagnostic setting (Rapid Access Diagnostics for Asthma study).

Results

Height, weight, body mass index and age were predictive of F ENO in univariate analysis using 1220 F ENO measurements. Only height remained significant after adjustment in the overall, nonatopic and atopic populations, and was included in the predictive equations for 50th, 75th 90th and 98th percentiles. The proposed percentile lines corresponded to the 57th (95% CI 53rd-61st), 80th (76th-83rd), 90th (87th-92nd) and 98th (96th-99th) percentiles in the SEATON cohort (660 measurements). When tested in 73 symptomatic treatment-naïve children and young adults (median (interquartile range) age: 11 (8-14) years), an F ENO >90th percentile gave a 96% specificity and positive predictive value of 97%, identifying 59% of children who were subsequently diagnosed with asthma after extensive testing.

Conclusion

We developed a height-based F ENO percentile chart which quantifies the probability of asthma in symptomatic children and merits further validation towards clinical implementation.

Elevated nitric oxide and carbon monoxide concentration in nasal-paranasal sinus air as a diagnostic tool of migraine: a case - control study

BACKGROUND

A recent study showed that 60-s paranasal air suction results in an immediate pain relief in acute migraine. This is the study to assess the Nitric Oxide (NO) and Carbon Monoxide (CO) concentration in nasal-paranasal sinus air of migraine patients and to compare it with healthy controls.

METHODOLOGY

The NO and CO levels of air sucked out from nasal-paranasal sinuses of 20 migraine adolescent and young adults among school students, aged 16 -19 years, and 22 healthy similar aged school students as controls were measured as key responses using a portable NO and a portable CO analyzer.

RESULTS

Patients had comparatively high values compared to the controls for paranasal NO (both left and right sides), paranasal CO (both left and right sides), Fraction Exhaled NO (FeNO) and Fraction Exhaled CO (FeCO). Patients had median paranasal NO contents of 132.5 ppb and 154 ppb on left and right sides respectively compared to 36 ppb and 34.5 ppb corresponding values in controls (P <  0.0001). Similar pattern was observed with paranasal CO (P <  0.0001). FeNO and FeCO content were also higher in patients (P <  0.0001). Receiver characteristic operating curves of all gas measurements showed that they all could classify patients and controls effectively and NO was the most effective followed by paranasal CO. After air suction, the mean pain scores of general headache and tenderness dropped by a very large margin in migraine patients (P <  0.0001).

CONCLUSIONS

Suctioned out high nasal-paranasal sinus NO and CO levels can be used to distinguish migraine patients from healthy subjects. In fact, suctioned out paranasal NO measurements of both sides with a cutoff point of 50 ppb provided a perfect classification of patients and controls. Increased sinus NO and CO during acute episode of migraine is an observation we had and we agree that further studies are needed to conclude that NO and CO can be a causative molecule for migraine headache.

TRAIL REGISTRATION

Clinical Trial Government Identification Number - 1548/2016. Ethical Clearance Granted Institute - Medical Research Institute, Colombo, Sri Lanka (No 38/2016). Sri Lanka Clinical Trial Registration number: SLCTR/ 2017/018 (29/06/2017). Approval Granting Organization to use the device in the clinical trial- National Medicines Regulatory Authority Sri Lanka (16/06/2018), The device won award at Geneva international inventers exhibition in 2016 and President award in 2018 in Sri Lanka. It is a patented device in Sri Lanka and patent number was SLKP/1/18295. All methods were carried out in accordance with CONSORT 2010 guidelines.

Patterns and determinants of exhaled nitric oxide trajectories in schoolchildren over a 7-year period

Fractional exhaled nitric oxide (F _ENO50 ), a marker of allergic airway inflammation, is used in respiratory research and asthma clinical care; however, its trajectory with increasing age during childhood has not been well characterised. We examined F _ENO50 longitudinally during a period of important somatic growth to describe trajectories across childhood and adolescence in healthy participants and evaluate clinical factors as potential determinants of trajectories.F _ENO50 was collected at six visits over 8 years in a population-based cohort of 1791 schoolchildren without asthma (median age at entry 8.4 years). Smooth sex-specific F _ENO50 trajectories were estimated using generalised additive mixed models, with participant-level random effects. We evaluated whether sex-specific trajectories were influenced by race/ethnicity, body mass index (BMI) percentile, allergic rhinitis or puberty.Different F _ENO50 patterns were observed by sex in later childhood and several factors were associated with either F _ENO50 level or change in F _ENO50 as participants aged. F _ENO50 -age trajectories were similar by sex until age ∼11.5 years, after which males had greater F _ENO50 change than females. This divergence in F _ENO50 -age trajectories coincides with puberty. Males with higher starting BMI percentile had attenuated F _ENO50 -age slopes. Among males, F _ENO50 levels were lower in non-Hispanic white subjects. Among both sexes, participants with rhinitis had higher F _ENO50 F _ENO50 levels within individuals tracked over time; however, there was considerable variation in F _ENO50 patterns across participants.F _ENO50 trajectories from longitudinal data provide evidence of sex differences coinciding with puberty, suggesting potential hormone link. Improved understanding of determinants of F _ENO50 trajectories is needed to realise the potential for using individualised predicted F _ENO50 trajectories.

Does Ramadan Fasting Affect Spirometric Data of Healthy Adolescents?

Purpose:

Several studies raised the effects of Ramadan fasting on healthy adults spirometric data, but none was performed in children. The aim of this study was to compare the spirometric data of a group of faster adolescents (n = 26) with an age-matched non-faster one (n = 10).

Methods:

This comparative quasi-experimental study, including 36 healthy males aged 12 to 15 years, was conducted during the summer 2015 (Ramadan: June 18 to July 16). Three sessions (Before-Ramadan [Before-R], Mid-Ramadan [Mid-R], After-Ramadan [After-R]) were selected for spirometry measurements. Spirometry was performed around 5.5 to 3.5 h before sunset and the spirometric data were expressed as percentages of local spirometric norms.

Results:

The two groups of fasters and non-fasters had similar ages and weights (13.35 ± 0.79 vs 12.96 ± 0.45 years, 46.8 ± 9.2 vs 41.7 ± 12.6 kg, respectively). There was no effect of Ramadan fasting on forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), FEV₁/FVC, peak expiratory flow, and maximal mid-expiratory flow. For example, during the Before-R, Mid-R, and After-R sessions, there was no significant difference between the fasters and non-fasters mean FVC (101 ± 11 vs 99 ± 14, 101 ± 12 vs 102 ± 14, 103 ± 11 vs 104 ± 13, respectively) or FEV₁ (101 ± 13 vs 96 ± 16, 98 ± 11 vs 97 ± 16, 101 ± 10 vs 98 ± 16, respectively).

Conclusions:

Ramadan fasting had no interaction effect with the spirometric data of Tunisian healthy male adolescents.

School-aged asthma children with high fractional exhaled nitric oxide levels and lung dysfunction are at high risk of prolonged lung dysfunction

Background

Long-term management of bronchial asthma based on the fractional exhaled nitric oxide (FeNO) value alone is not conclusive yet. Therefore, we combined FeNO testing and spirometry, a commonly used test in routine practice, to evaluate acute exacerbation and respiratory function in children with bronchial asthma.

Objective

We combined FeNO testing and spirometry, commonly used in routine practice, to evaluate acute exacerbations and respiratory function in children with bronchial asthma.

Methods

Subjects were school aged children 7 years and older with bronchial asthma who underwent FeNO testing in January 2015 to May 2016. We evaluated the changes in the frequency of acute exacerbations and respiratory function in the 30 subsequent months. Subjects were divided into 2 groups: those with initial FeNO levels ≥ 21 parts per billion (ppb) (high FeNO) and < 20 ppb (normal FeNO) groups.

Results

There were 48 children (33 boys) in the high FeNO group and 68 children (46 boys) in the normal FeNO group. Spirometry was conducted on 83 children (72%) prior to the initial FeNO test, revealing no difference in the ratio of detecting lung dysfunction between the 2 groups. The observation period was 25.8 ± 0.7 and 24.7 ± 0.6 months for the high and normal FeNO groups, respectively. The children in the high FeNO group with lung dysfunction in the initial FeNO test continued to exhibit lung dysfunction at the test at 30 months. In the normal FeNO group, even if lung dysfunction was observed at the initial FeNO, it improved within the 20-month point, and the improvement was maintained thereafter.

Conclusion

Children with bronchial asthma with high FeNO levels and lung dysfunction are at a higher risk of prolonged lung dysfunction.

Normal values of offline exhaled and nasal nitric oxide in healthy children and teens using chemiluminescence

Nitric oxide (NO) can be used to detect respiratory or ciliary diseases. Fractional exhaled nitric oxide (FeNO) measurement can reflect ongoing eosinophilic airway inflammation and has a diagnostic utility as a test for asthma screening and follow-up while nasal nitric oxide (nNO) is a valuable screening tool for the diagnosis of primary ciliary dyskinesia. The possibility of collecting airway gas samples in an offline manner offers the advantage to extend these measures and improve the screening and management of these diseases, but normal values from healthy children and teens remain sparse.

METHODS

Samples were consecutively collected using the offline method for eNO and nNO chemiluminescence measurement in 88 and 31 healthy children and teens, respectively. Offline eNO measurement was also performed in 30 consecutive children with naïve asthma and/or respiratory allergy.

RESULTS

The normal offline eNO value was determined by the following regression equation -8.206 + 0.176 × height. The upper limit of the norm for the offline eNO value was 27.4 parts per billion (ppb). A separate analysis was performed in children, pre-teens and teens, for which offline eNO was 13.6 ± 4.7 ppb, 16.3 ± 13.7 ppb and 20.0 ± 7.2 ppb, respectively. The optimal cut-off value of the offline eNO to predict asthma or respiratory allergies was 23.3 ppb, with a sensitivity and specificity of 77% and 91%, respectively. Mean offline nNO was determined at 660 ppb with the lower limit of the norm at 197 ppb.

CONCLUSION

The use of offline eNO and nNO normal values should favour the widespread screening of respiratory diseases in children of school age in their usual environment.

Does Ethnicity Influence Fractional Exhaled Nitric Oxide in Healthy Individuals?: A Systematic Review

BACKGROUND

Fractional exhaled nitric oxide (Feno) is used clinically as a biomarker of eosinophilic airway inflammation. Awareness of the factors influencing Feno values is important for valid clinical interpretation.

METHODS

We undertook a systematic review of PubMed, Cochrane Library, Scopus, and Web of Science databases and reference lists of included articles to evaluate whether ethnicity influences Feno values, and to determine if this influence affects clinical interpretation according to current guidelines. We included all studies that performed online Feno measurements on at least 25 healthy, non-Caucasian individuals, and examined the effect of ethnicity on Feno.

RESULTS

From 62 potential studies, 12 studies were included. One study recruited only children (< 12 years of age), six studies recruited children and/or adolescents, four studies recruited adults only, and a single study involved children, adolescents, and adults. In total, 16 different ethnic populations representing 11 ethnicities were studied. Ethnicity was considered a significant influencing factor in 10 of the included studies. We found the geometric mean Feno to be above the normal healthy range in two studies. We also identified five studies in which at least 5% of participants had Feno results above the age-specific inflammatory ranges.

CONCLUSIONS

Ethnicity influences Feno values, and for some ethnic groups this influence likely affects clinical interpretation according to current guidelines. There is a need to establish healthy Feno reference ranges for specific ethnic groups to improve clinical application.

Fraction of exhaled nitric oxide in healthy Chilean schoolchildren aged 8-15 years

BACKGROUND

The fraction of exhaled nitric oxide (FENO) measured using portable devices is increasingly used in the clinical setting to assess asthmatic children. However, there is little and variable information on the reference values obtained using these devices in healthy children from different populations.

METHODS

190 healthy non-smoker children (8-15 years old) were randomly selected from public schools participating in this study. The objective was to determine FENO reference values for healthy Chilean schoolchildren. Healthy individuals were identified by medical interview and parent questionnaire on the use of asthma medications, and current and past symptoms of asthma, rhinoconjunctivitis and eczema. FENO was measured at schools using a portable device with electrochemical sensor (NIO MINOX). Reference values of FENO were expressed as geometric mean and upper limit of the 95% reference interval (right-sided). The relationship of FENO with gender, age, height, body mass, and other factors was assessed by multiple regression, and the difference between groups was contrasted by ANOVA.

RESULTS

The FENO geometric mean was 15.4ppb with a 95% reference interval upper limit (right-sided), of 27.4ppb (90%CI 25.6-29.2). The 5th and 95th percentiles were 9.0ppb and 28.0ppb, respectively. Height was the only factor significantly associated to FENO (p=0.022). There was no significant difference in mean FENO regarding age, gender, weight, parent reported rhinoconjunctivitis and eczema.

CONCLUSION

This study suggests that FENO values higher than 27ppb are likely to be abnormal and would reflect airway inflammation in children as those in the present study.

Fraction of exhaled nitric oxide in healthy elderly Tunisian subjects

INTRODUCTION

Exhaled-fraction-of-nitric-oxide (Fe_NO) norms are absent in healthy elderly North-African subjects.

OBJECTIVES

i) to identify Fe_NO influencing factors of elderly Tunisians older 50 years and more; ii) to assess the applicability of some published Fe_NO norms for elderly in local population; iii) to set-up Fe_NO norms and to prospectively evaluate their validity in two elderly validation-groups (healthy and asthmatic subjects).

METHODS

A convenience sample of healthy and asthmatic elderly Tunisians was recruited. Subjects responded to a medical questionnaire and then Fe_NO 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.

RESULTS

No significant factor, among those evaluated, influenced Tunisian elderly Fe_NO values. The available published Fe_NO norms did not reliably predict Fe_NO in Tunisian elderly population. The mean ± SD (minimum-maximum) of Fe_NO (ppb) for group I was 14 ± 6 (3-34). For Tunisian people, each elderly Fe_NO value higher than 34 ppb will be considered as abnormal. There was no statistical significant difference between Fe_NO (ppb) mean values of group I and groups II (15 ± 8) or III (18 ± 13). No subject of group II had a Fe_NO value higher than 34 ppb. Thirty percent of group III subjects had a Fe_NO value higher than 34 ppb.

CONCLUSION

In practice, Fe_NO value of more than 34 ppb is considered abnormal in elderly Tunisian population.

Fraction of exhaled nitric oxide (FeNO ) norms in healthy Tunisian adults

Aims. To establish Fe_NO norms for healthy Tunisian adults aged 18–60 years and to prospectively assess their reliability. Methods. This was a cross-sectional analytical study. A convenience sample of healthy Tunisian adults was recruited. Subjects responded to a medical questionnaire, and then Fe_NO levels were measured by an online method (Medisoft, Sorinnes (Dinant), Belgium). Clinical, anthropometric, and plethysmographic data were collected. All analyses were performed on natural logarithm values of Fe_NO. Results. 257 adults (145 males) were retained. The proposed reference equation to predict Fe_NO value is lnFe_NO (ppb) = 3.47−0.56× height (m). After the predicted Fe_NO value for a given adult was computed, the upper limit of normal could be obtained by adding 0.60 ppb. The mean ± SD (minimum-maximum) of Fe_NO (ppb) for the total sample was 13.54 ± 4.87 (5.00–26.00). For Tunisian and Arab adults of any age and height, any Fe_NO value greater than 26.00 ppb may be considered abnormal. Finally, in an additional group of adults prospectively assessed, we found no adult with a Fe_NO higher than 26.00 ppb. Conclusion. The present Fe_NO norms enrich the global repository of Fe_NO norms that the clinician can use to choose the most appropriate norms.