Effect of changing reference equations for spirometry interpretation in Thai people

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Clinical Diagnostics

Background:

• Spirometry interpretation varies based on reference equations, potentially leading to misdiagnosis.
• No prior studies evaluated discordance between Global Lungs Initiative (GLI) 2012, NHANES III, Knudson, and Siriraj equations in Thai individuals.
• Accurate spirometry interpretation is crucial for diagnosing and managing respiratory diseases.

Purpose of the Study:

• To determine differences and agreement in spirometry results using four distinct reference equations in a Thai population.
• To assess the impact of using GLI2012, NHANES III, Knudson, and Siriraj equations on spirometry interpretation.
• To provide data for selecting appropriate reference equations for Thai adults.

Main Methods:

• Retrospective analysis of 2,492 spirometry results from Thai adults (aged 8-80).
• Interpretation of spirometry data using GLI2012, NHANES III, Knudson, and Siriraj reference equations.
• Statistical analysis including Nominal Analysis of Variance (NANOVA) and Kappa statistic to evaluate differences and agreement.

Main Results:

• Significant differences (P<0.001) were observed in spirometry diagnosis and severity classification across the four equations.
• Moderate to good agreement levels were found among the equations (Kappa values for diagnosis: 0.56-0.77; for severity: 0.67-0.82).
• The choice of reference equation impacts the interpretation of respiratory function patterns and their severity.

Conclusions:

• The use of GLI2012, NHANES III, Knudson, and Siriraj reference equations significantly alters spirometry data interpretation in Thai adults.
• Findings underscore the importance of equation selection for accurate clinical assessment.
• Further research may be needed to establish the most appropriate reference equations for the Thai population.