Elevated exhaled nitric oxide in anaphylaxis with respiratory symptoms

Area of Science:

• Allergy and Immunology
• Respiratory Medicine
• Diagnostic Biomarkers

Background:

• Anaphylaxis is a severe allergic reaction with diagnostic challenges, often relying solely on clinical symptoms.
• Fractional exhaled nitric oxide (FeNO) is a marker of airway inflammation, influenced by atopic status.
• The utility of FeNO in diagnosing anaphylaxis requires investigation.

Purpose of the Study:

• To evaluate the role of fractional exhaled nitric oxide (FeNO) measurements in patients experiencing anaphylaxis.
• To determine if FeNO levels can aid in the diagnosis of anaphylaxis, especially in differentiating it from other conditions.

Main Methods:

• FeNO levels were measured in 52 adult patients within 24 hours of anaphylaxis onset and again after one month.
• Measurements were repeated a third time in some patients two months or more post-onset.
• Analysis included comparisons between initial and follow-up measurements, with stratification based on asthma history and respiratory symptoms.

Main Results:

• Overall FeNO levels did not differ significantly between acute and one-month post-anaphylaxis measurements in all 52 patients.
• In 43 patients without a history of asthma, FeNO levels significantly decreased from acute onset (36.7 ± 27.5 ppb) to one month later (28.8 ± 19.5 ppb).
• This FeNO decrease was observed in patients with respiratory symptoms (31 patients) but not in those without (12 patients).

Conclusions:

• Elevated FeNO levels in anaphylactic patients without asthma are associated with the presence of respiratory symptoms.
• The findings suggest FeNO may be a useful diagnostic indicator for anaphylaxis in specific patient subgroups.
• Further prospective studies are needed to confirm the diagnostic value of FeNO in anaphylaxis.