Evaluation of the peripheral blood eosinophil count as a predictor for fractional exhaled nitric oxide or bronchodilator reversibility test outcome

The value of bronchodilator response in FEV1 and FeNO for differentiating between chronic respiratory diseases: an observational study

BACKGROUND

There is no uniform standard for a strongly positive bronchodilation test (BDT) result. In addition, the role of bronchodilator response in differentiating between asthma, chronic obstructive pulmonary disease (COPD), and asthma-COPD overlap (ACO) in patients with a positive BDT result is unclear. We explored a simplified standard of a strongly positive BDT result and whether bronchodilator response combined with fractional exhaled nitric oxide (FeNO) can differentiate between asthma, COPD, and ACO in patients with a positive BDT result.

METHODS

Three standards of a strongly positive BDT result, which were, respectively, defined as post-bronchodilator forced expiratory volume in 1-s responses (ΔFEV1) increasing by at least 400 mL + 15% (standard I), 400 mL (standard II), or 15% (standard III), were analyzed in asthma, COPD, and ACO patients with a positive BDT result. Receiver operating characteristic curves were used to determine the optimal values of ΔFEV1 and FeNO. Finally, the accuracy of prediction was verified by a validation study.

RESULTS

The rates of a strongly positive BDT result and the characteristics between standards I and II were consistent; however, those for standard III was different. ΔFEV1 ≥ 345 mL could predict ACO diagnosis in COPD patients with a positive BDT result (area under the curve [AUC]: 0.881; 95% confidence interval [CI] 0.83-0.94), with a sensitivity and specificity of 90.0% and 91.2%, respectively, in the validation study. When ΔFEV1 was < 315 mL combined with FeNO < 28.5 parts per billion, patients with a positive BDT result were more likely to have pure COPD (AUC: 0.774; 95% CI 0.72-0.83).

CONCLUSION

The simplified standard II can replace standard I. ΔFEV1 and FeNO are helpful in differentiating between asthma, COPD, and ACO in patients with a positive BDT result.

Low Serum IL-18 Levels May Predict the Effectiveness of Dupilumab in Severe Asthma

Objective Dupilumab, a monoclonal antibody specific for the human interleukin (IL)-4 receptor α, is used to treat severe asthma, especially in patients with elevated blood eosinophil counts and fractional exhaled nitric oxide (FeNO). The therapeutic response to dupilumab is highly variable. In this study, we explored new serum biomarkers to accurately predict the effect of dupilumab and examine the effect of dupilumab based on changes in the clinical parameters and cytokine levels. Methods Seventeen patients with severe asthma treated with dupilumab were enrolled. Responders, defined as those with a >0.5-point decrease in the Asthma Control Questionnaire (ACQ) score after 6 months of treatment, were included. Results There were 10 responders and 7 non-responders. Serum type 2 cytokines were equivalent between responders and non-responders; the baseline serum IL-18 level was significantly lower in responders than in non-responders (responders, 194.9±51.0 pg/mL; non-responders, 323.4±122.7 pg/mL, p=0.013). The cut-off value of IL-18 at 230.5 pg/mL could be used to distinguish non-responders from responders (sensitivity 71.4, specificity 80.0, p=0.032). Conclusion A low baseline serum IL-18 level may be a useful predictor of an unfavorable response to dupilumab in terms of the ACQ-6.

Markers of eosinophilic airway inflammation in patients with asthma and allergic rhinitis

Background: Measurement of airway inflammation is an important step to determine phenotype of asthma and allergic rhinitis (AR). Objective: To assess the level of nitric oxide in exhaled air (FeNO), nasal fraction of nitric oxide (nasal NO), their relationship with clinical control and blood eosinophils in patients with steroid-naive mild and moderate asthma and AR. Methods: One hundred forty-seven patients (65 men), ages 26-49.5 years (mean age, 32 years) with AR (n = 81) or AR and concomitant asthma (n = 46) and 20 healthy subjects were included in a single-center cohort study. All the patients underwent spirometry with reversibility test. Control of asthma and AR was assessed by using the Asthma Control Questionnaire and the visual analog scale, respectively. Levels of FeNO and nasal NO were measured by chemiluminescent analyzer, peripheral blood eosinophils were counted by automatic analyzer. Results: The FeNO level was significantly elevated in the patients with asthma and concomitant AR compared with the healthy subjects and was associated with control of both asthma and AR. There was no correlation between nasal NO and control of AR. Receiver operating characteristic analysis revealed that the level of eosinophils of 150 cells/μL may be a cutoff for lower airway eosinophilic inflammation. Blood eosinophils count was unable to distinguish eosinophilic and non-eosinophilic upper airway inflammation. Conclusion: We confirm that FeNO but not nasal NO is a marker of eosinophilic airway inflammation in patients with mild-moderate steroid-naive AR and concomitant asthma. A blood eosinophil level of ≥150 cells/µL may be a simple marker of eosinophilic airway inflammation in patients with asthma. However, its low specificity requires repeated measurements and use in combination with other biomarkers.

Eosinophilic granulomatosis with polyangiitis in allergic asthma: Efforts to make early diagnosis possible

Background: Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare autoimmune disease that can affect multiple organ systems in the body. A majority of patients with EGPA present with asthma-like symptoms and may be misdiagnosed with refractory asthma. It is necessary to distinguish EGPA from asthma and provide a theoretical basis for effective future prevention and treatment. Objective: This study aimed to compare the clinical features of EGPA and the clinical features of allergic asthma in an effort to make an early diagnosis possible. Methods: We reviewed the basic information, test results, pre-onset conditions, and prognosis of 44 adult patients with EGPA who were admitted to our hospital between January 2013 and June 2021, and conducted a 1:1 matched case-control study to compare patients with EGPA and patients with allergic asthma. Results: The 44 patients with EGPA were older than those with allergic asthma, but more than half of the patients with EGPA had been diagnosed with bronchial asthma, with a history of 10 months to 40 years, and had previously used inhalers or systemic steroids. The proportion of male-to-female cases was ∼1:1, with seven antineutrophil cytoplasmic antibodies (ANCA) positive cases (15.9%), 20 limited EGPA cases (45.45%), and 24 systemic EGPA cases (54.55%). Although the peripheral blood eosinophil count and percentage were lower in the male patients than in the female patients, male patients with higher five-factor scores might indicate worse prognosis. The fractional exhaled nitric oxide (FeNO) level, eosinophil percentage and count, and total immunoglobulin E (IgE) level were higher in the EGPA group than in the allergic asthma group. Unlike in allergic asthma, the FeNO level is not correlated with the blood eosinophil count or percentage in EGPA. Seven patients received cardiac emission computed tomography (ECT) tests, with abnormalities suggested in six patients. Results of an electrocardiogram, color-Doppler echocardiography, myocardial enzyme level, and troponin level suggested no obvious abnormality. Conclusion: The proportion of patients with EGPA who tested positive for ANCA is not high, and patients with high eosinophil counts should be alert to the possibility of having EGPA. For patients with infiltration of eosinophils into the airway, a diagnosis should not be based on peripheral blood eosinophil counts. It is recommended that the FeNO level and pulmonary function should also be monitored for patients who present with symptoms in other body systems. The sensitivity of cardiac ECT tests is higher than routine tests, so timely screening by cardiac ECT is recommended for all patients with EGPA.