The evaluation of changing from the Thai spirometry to the Global Lung Initiative 2012 reference equations on spirometry interpretation in Thai People

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Warawut Chaiwong Chaicharn Pothirat Chalerm Liwsrisakun Sureeporn Uthaikhup


Background: Spirometry is the most common lung function test for determining diagnosis and severity of respiratory diseases. Inappropriate reference equations used can lead to potential errors in the interpretation of spirometry results. The GLI2012 reference equations have recently been recommended for worldwide use but have not been studied in Thai people.

Objective: To quantify the differences and agreements on the interpretation of spirometry results between the Siriraj and GLI2012 predicted values in Thai people.

Methods: A retrospective study of 2,582 spirometry results were derived from Thai people (age ≥ 18 years old) who were referred by their physicians for spirometric testing between January 2005 and December 2015. The spirometry results were estimated using both Siriraj and GLI2012 reference equations. Respiratory function patterns were interpreted as normal, restriction, obstruction, or mixed defect. Level of abnormal patterns were classified as mild, moderate, moderately severe, severe or very severe. Chi-square test was used to analyze differences in classification for the diagnosis and severity and Kappa statistic was used to determine agreement of interpretation between the Siriraj and GLI2012 references equations.

Results: The spirometry diagnosis and the severity classification were significantly different between the two sets of reference equations (p<0.001). The levels of agreement for diagnosis and level of severity between the two sets of reference equations were good (Kappa values were 0.76 and 0.69, p<0.001, respectively).

Conclusion: Changing from the Siriraj to GLI2012 reference equations alters the interpretation of spirometry results in Thai people, which may modify clinical decision in management of respiratory diseases.


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Chaiwong W, Pothirat C, Liwsrisakun C, Uthaikhup S. The evaluation of changing from the Thai spirometry to the Global Lung Initiative 2012 reference equations on spirometry interpretation in Thai People. Thai Journal of Physical Therapy [Internet]. 19Jun.2018 [cited 20Jul.2018];40(2):69-8. Available from:
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