Measurement of exhaled nitric oxide in the evaluation for eosinophilic esophagitis in children

Exhaled Nitric Oxide as Biomarker of Type 2 Diseases

Nitric oxide (NO) is a short-lived gas molecule which has been studied for its role as a signaling molecule in the vasculature and later, in a broader view, as a cellular messenger in many other biological processes such as immunity and inflammation, cell survival, apoptosis, and aging. Fractional exhaled nitric oxide (FeNO) is a convenient, easy-to-obtain, and non-invasive method for assessing active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid the diagnosis and monitoring of several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory and/or immunological conditions, including allergic rhinitis, chronic rhinosinusitis with/without nasal polyps, atopic dermatitis, eosinophilic esophagitis, and food allergy. In this review, we aim to provide an extensive overview of the current state of knowledge about FeNO as a biomarker in type 2 inflammation, outlining past and recent data on the application of its measurement in patients affected by a broad variety of atopic/allergic disorders.

Diagnostic role of fractional exhaled nitric oxide in pediatric eosinophilic esophagitis, relationship with gastric and duodenal eosinophils

BACKGROUND

Eosinophilic esophagitis (EoE) is an eosinophilic-predominant inflammation of the esophagus diagnosed by upper endoscopy and biopsies. A non-invasive and cost-effective alternative for management of EoE is being researched. Previous studies assessing utility of fractional exhaled nitric oxide (FeNO) in EoE were low powered. None investigated the contribution of eosinophilic inflammation of the stomach and duodenum to FeNO.

AIM

To assess the utility of FeNO as a non-invasive biomarker of esophageal eosinophilic inflammation for monitoring disease activity.

METHODS

Patients aged 6-21 years undergoing scheduled upper endoscopy with biopsy for suspected EoE were recruited in our observational study. Patients on steroids and with persistent asthma requiring daily controller medication were excluded. FeNO measurements were obtained in duplicate using a chemiluminescence nitric oxide analyzer (NIOX MINO, Aerocrine, Inc.; Stockholm, Sweden) prior to endoscopy. Based on the esophageal peak eosinophil count (PEC)/high power field on biopsy, patients were classified as EoE (PEC ≥ 15) or control (PEC ≤ 14). Mean FeNO levels were correlated with presence or absence of EoE, eosinophil counts on esophageal biopsy, and abnormal downstream eosinophilia in the stomach (PEC ≥ 10) and duodenum (PEC ≥ 20). Wilcoxon rank-sum test, Spearman correlation, and logistic regression were used for analysis. P value < 0.05 was considered significant.

RESULTS

We recruited a total of 134 patients, of which 45 were diagnosed with EoE by histopathology. The median interquartile range FeNO level was 17 parts per billion (11-37, range: 7-81) in the EoE group and 12 parts per billion (8-19, range: 5-71) in the control group. After adjusting for atopic diseases, EoE patients had significantly higher FeNO levels as compared to patients without EoE (Z = 3.33, P < 0.001). A weak yet statistically significant positive association was found between the number of esophageal eosinophils and FeNO levels (r = 0.30, P < 0.005). On subgroup analysis within the EoE cohort, higher FeNO levels were noted in patients with abnormal gastric (n = 23, 18 vs 15) and duodenal eosinophilia (n = 28, 21 vs 14); however, the difference was not statistically significant.

CONCLUSION

After ruling out atopy as possible confounder, we found significantly higher FeNO levels in the EoE cohort than in the control group.

Plasma Biomarkers and Fractional Exhaled Nitric Oxide in the Diagnosis of Eosinophilic Esophagitis

OBJECTIVES

Eosinophilic esophagitis (EoE) is a chronic disease which requires endoscopy with biopsies for diagnosis and monitoring. We aimed to identify a panel of non-invasive markers that could help identify patients with active EoE.

METHODS

In this prospective cohort study, we enrolled 128 children aged 5-18 years old, scheduled for endoscopy for suspected esophageal or peptic disease. On the day of the endoscopy, fractionated exhaled nitric oxide (FeNO) was measured; and blood was collected for peripheral absolute eosinophil count (AEC), plasma amino acids, and plasma polyamine analysis. Patients were grouped into controls (n = 91), EoE in remission (n = 16), or active EoE (n = 21), based on esophageal eosinophilia and history of EoE.

RESULTS

AEC was not statistically significant different among the groups compared ( P = 0.056). Plasma amino acids: citrulline (CIT), β-alanine (β-ALA), and cysteine (CYS) were higher in active EoE compared to controls ( P < 0.05). The polyamine spermine was lower in active EoE versus controls ( P < 0.05). Receiver operator characteristic (ROC) curve to assess the predictive capability of a combined score made of FeNO, β-ALA, CYS, and spermine had an area under curve (AUC) of 0.90 (95% CI: 0.80-0.96) in differentiating active EoE from controls and 0.87 (95% CI: 0.74-1.00) when differentiating active EoE from EoE in remission.

CONCLUSION

A panel comprising FeNO, 2 plasma amino acids (β-ALA, CYS) and the polyamine spermine can be used as a non-invasive tool to differentiate active EoE patients from controls.

Minimally invasive biomarker studies in eosinophilic esophagitis: A systematic review

BACKGROUND

Eosinophilic esophagitis (EoE) is a chronic, inflammatory disease of the esophagus that currently requires repeated endoscopic biopsies for diagnosis and monitoring because no reliable noninvasive markers have been identified.

OBJECTIVE

To identify promising minimally invasive EoE biomarkers and remaining gaps in biomarker validation.

METHODS

We performed a systematic review of EMBASE, Ovid MEDLINE, PubMed, and Web of Science from inception to June 6, 2017. Studies were included if patients met the 2007 consensus criteria for EoE diagnosis, a minimally invasive biomarker was assessed, and the study included at least 1 control for comparison.

RESULTS

The search identified 2094 studies, with 234 reviewed at full-text level, and 49 included in the analysis (20 adult, 19 pediatric, 7 pediatric and adult, and 3 not stated). Most (26 of 49) were published after 2014. Thirty-five studies included healthy controls, 9 analyzed atopic controls, and 29 compared samples from patients with active and inactive EoE. Minimally invasive biomarkers were obtained from peripheral blood (n = 41 studies), sponge or string samples (n = 3), oral or throat swab secretions (n = 2), breath condensate (n = 2), stool (n = 2), and urine (n = 2). The most commonly reported biomarkers were peripheral blood eosinophils (n = 16), blood and string eosinophil granule proteins (n = 14), and eosinophil surface or intracellular markers (n = 12). EoE biomarkers distinguished active EoE from healthy controls in 23 studies, atopic controls in 2 studies, and inactive EoE controls in 20 studies.

CONCLUSION

Several promising minimally invasive biomarkers for EoE have emerged; however, few are able to differentiate EoE from other atopic diseases.

Poor Relationship Between Fractionated Exhaled Nitric Oxide and Disease Activity in Eosinophilic Esophagitis

Current eosinophilic esophagitis care requires monitoring with repeat endoscopy and biopsy, which has significant cost, risk, and inconvenience for patients. Fractionated exhaled nitric oxide testing (FeNO) is a standardized non-invasive test with proven utility in evaluation of asthma. Elevated FeNO has reported use in other eosinophilic inflammatory conditions; however, its use in eosinophilic esophagitis has not been fully evaluated. To assess the utility of FeNO in predicting severity of eosinophilic esophagitis activity. Fifty patients received fractionated exhaled nitric oxide testing within 1 week of endoscopic evaluation with biopsy for determination of peak eosinophil counts. Presence of furrows was also evaluated with respect to FeNO levels. Spearman correlation was calculated between FeNO and peak eosinophil counts (PEC) with subgroup analysis performed based on PPI use. Spearman correlation was performed on the change in FeNO and PEC on the patients receiving repeat testing. FeNO was poorly correlated to PEC (Spearman correlation 0.22). With a cut-off FeNO value of > 40 ppb, specificity of FeNO for detecting presence of ≥ 15 eos/hpf was 0.94 and sensitivity was 0.16. FeNO showed weak relationship to presence of furrows. Within the subgroup of patients not taking PPI, the spearman correlation was 0.21. Delta- FeNO versus Delta-PEC had spearman correlation of 0.72 for patients receiving repeat testing. FeNO likely has limited clinical utility for predicting severity of esophageal eosinophilia. In patients with FeNO levels > 40 ppb, specificity of testing was high, but very few patients reached this FeNO level.

Promising Modalities to Identify and Monitor Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is an allergen-mediated condition characterized by symptoms of esophageal dysfunction and histologic evidence of intense eosinophilic inflammation involving the esophagus in the absence of overlapping conditions such as gastroesophageal reflux disease. Since the initial description as a distinct entity approximately 2 decades ago, there has been a remarkable increase in the recognition of this clinicopathologic entity. The current approach to diagnose and monitor EoE requires repeated esophagogastroduodenoscopies, with associated sedation/anesthesia, to visualize mucosal abnormalities, and to obtain multiple biopsy specimens for histologic assessment and to evaluate treatment response. Frequent esophagogastroduodenoscopies with multiple biopsies can increase the risk of procedural complications, place significant financial burden on families, and escalate health care costs. In addition, this burdensome approach may contribute toward delayed diagnosis and suboptimal monitoring, thereby increasing the likelihood of complications such as esophageal narrowing and stricture formation, which may require escalation of care including endoscopic interventions. Clinical progression and complications associated with EoE can be attenuated through early identification and optimal management. Therefore, developing reliable, safe, less-cumbersome, and cost-effective modalities for early diagnosis and effective monitoring of EoE is an area of active research. These efforts have been substantially supported by the development of new biomaterials, analytic methodologies, and the application of novel concepts. Herein, we summarize modalities that have shown promise to advance the diagnosis and monitoring of EoE and could improve the care of affected individuals and advance the field.

Prospective assessment of serum periostin as a biomarker for diagnosis and monitoring of eosinophilic oesophagitis

BACKGROUND

Periostin is highly expressed in eosinophilic oesophagitis (EoE), but has not been extensively studied as a non-invasive biomarker.

AIM

To assess whether serum periostin distinguished EoE from controls at baseline, had utility for monitoring treatment response, or was associated with IL-13 levels.

METHODS

This was a sub-analysis of a prospective cohort study of adults undergoing out-patient upper endoscopy. Incident cases of EoE were diagnosed per consensus guidelines. Controls were subjects with either GERD or dysphagia without EoE. EoE patients were treated with swallowed/topical steroids and had repeat endoscopy/biopsy. Serum periostin levels for cases and controls were compared at baseline, and pre/post-treatment levels were compared for cases. Serum IL-13 and tissue expression of periostin were also assessed.

RESULTS

A total of 61 incident EoE cases and 87 controls were analysed. Despite a marked increase in tissue periostin expression in cases, the median baseline serum periostin level was only slightly higher in cases than controls (22.1 ng/mL vs. 20.7; P = 0.04); there was no change in post-treatment levels. There was also no difference in serum periostin for cases by histologic response or atopic status. There was a strong trend towards higher serum IL-13 levels in cases in the highest periostin quartile (57.1 pg/mL vs. 2.6; P = 0.07).

CONCLUSIONS

Serum periostin levels were similar in cases and controls, and there were no changes post-treatment. Given elevated IL-13 levels in the EoE patients with the highest periostin levels, future studies could explore periostin as a biomarker in EoE, perhaps in the setting of anti-IL-13 therapy.