Evaluation of the Global Lung Function Initiative 2012 reference values for spirometry in an Iranian population

Area of Science:

• Pulmonary Medicine
• Spirometry
• Respiratory Physiology

Background:

• Spirometry is crucial for diagnosing and monitoring chronic obstructive pulmonary disease (COPD).
• The Global Lung Function Initiative 2012 (GLI-2012) spirometric norms are widely used but their applicability across diverse ethnic groups is debated.
• Evaluating the GLI-2012 norms in specific populations is essential for accurate respiratory health assessments.

Purpose of the Study:

• To assess the applicability of the GLI-2012 spirometric reference values in a healthy Iranian population.
• To determine if GLI-2012 norms accurately reflect lung function parameters in Iranian adults and children.
• To identify potential discrepancies in spirometry interpretations when using GLI-2012 norms for Iranians.

Main Methods:

• A cross-sectional study involving 622 healthy, non-smoking Iranians (204 males, 418 females, aged 4-82 years).
• Calculation of Z-scores for forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and forced expiratory flow averaged over the middle 50% of FVC (FEF25-75%).
• Analysis of mean Z-scores and the prevalence of values below the lower limit of normal (LLN), with a clinical significance threshold set at a mean Z-score outside ±0.5.

Main Results:

• Mean Z-scores for FEV1, FVC, and FEV1/FVC were generally within acceptable ranges for adults, but FEF25-75% showed a significant negative deviation in males.
• The prevalence of FEV1/FVC below LLN was low in adults (≥21 years) but markedly higher in individuals under 21 years (46.2% in boys, 40.0% in girls).
• The GLI-2012 norms showed notable discrepancies, particularly for spirometric values in Iranian children under 10 years and potentially overestimating airway obstruction in those under 21.

Conclusions:

• The GLI-2012 spirometric reference values are not perfectly applicable to the Iranian population, especially in younger age groups.
• While GLI-2012 norms may be appropriate for Iranian adults over 21 years, caution is advised due to potential overestimation of airway obstruction in individuals under 21.
• Further research and potential ethnic-specific adjustments to spirometry norms are recommended for the Iranian population to ensure accurate respiratory disease diagnosis and management.