What question did this study set out to answer?

This study aims to determine the prevalence of small airway disease (SAD) in patients with post-viral cough and compare Z-scores and cut-off values for assessment.

May 20, 2026

C67-02 Cut-off Values or Z-scores? A Comparative Analysis of Impulse Oscillometry in Small Airway Assessment After Post-viral Cough

Key Points

This study aims to determine the prevalence of small airway disease (SAD) in patients with post-viral cough and compare Z-scores and cut-off values for assessment.
Descriptive cross-sectional study at a respiratory center involving patients with post-viral cough from May 2024 to August 2025.
SAD assessed using PulmoScan Oscillometry according to ERS guidelines applying R5-R20 and Z-score measurements.
Statistical analyses conducted using SPSS v30, comparing paired proportions with McNemar’s test and Chi-square tests.
Post-viral cough diagnosed in 48.4% (n = 181), with SAD prevalence at 60.2% using cut-off and only 27.8% using Z-scores (p < 0.001).
SAD observed in 67.1% of acute cough cases and 60.8% in subacute cases (p < 0.05).
FeNO values showed lower results in 86.6% of assessed patients, with no differences based on viral diagnosis, sex, or FeNO.

Abstract

Abstract Rationale The immunity debt hypothesis suggests increased vulnerability to pathogens due to reduced exposure during the pandemic. One year after COVID-19 restrictions ended, influenza rates exceeded 130% in winter and summer. Viral airway injury may cause small airway lesions linked to physiological dysfunction. Small airway disease (SAD) involves bronchiole narrowing from inflammation, edema, or bronchoconstriction, causing persistent cough. Respiratory passages 2 mm are assessed through oscillometry, with R5-R20 as the primary parameter in Z-score formulas. This study aimed to determine SAD prevalence in post-viral cough (PVC) patients and compare Z-scores and cut-offs. Methods A descriptive cross-sectional study was conducted at a respiratory center on patients with post-viral cough between May 2024 and August 2025. Cough was categorized as acute, subacute, or chronic. SAD was assessed using PulmoScan Oscillometry per ERS guidelines, defined by R5-R20 0.07 kPa/(L/s) and Z-score 1.645; X5, AX, and Fres were included. FeNO was measured in some patients. Frequencies, percentages, and parametric/non-parametric statistics were used. McNemar’s test compared paired proportions, and Chi-square test was used. SPSS v30 was used with p 0.05 significance. Results PVC was diagnosed in 48.4% (n = 181) of patients. 64.6% were female, mean age 45.6 years (SD 24.9), BMI 25.9 kg/m2 (SD 5.8). Most reported acute (49.7%) or subacute (28.8%) cough. Influenza was most prevalent (28.6%, n = 35), and FeNO (n = 112) showed lower values in 86.6% of cases. SAD prevalence using cutoff was 60.2%, but 27.8% with z-score (p 0.001). In acute and subacute cough, SAD was observed in 67.1% and 60.8% versus 31.8% and 29.4% (p 0.05). Similar trends appeared for X5, AX, and Fres. No differences were found between viral diagnosis, sex, and FeNO values. Conclusions Oscillometry shows clinical value for post-viral cough patients. SAD prevalence was higher using cutoff values versus Z-scores. Research is needed to define Latin American population cutoff levels. Results could enable earlier use of small-particle bronchodilators/corticosteroids. This abstract is funded by: None

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