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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.
2. Sood A, Dawson BK, Henkle JQ, Hopkins-Price P, Quails C. Effect of change of reference standard to NHANES III on interpretation of spirometric 'abnormality'. Int J Chron Obstruct Pulmon Dis. 2007; 2: 361-7.
3. Stanojevic S, Wade A, Stocks J. Reference values for lung function: past, present and future. Eur Respir J. 2010; 36: 12-9.
4. Lung function testing: selection of reference values and interpretative strategies. American Thoracic Society. Am Rev Respir Dis. 1991; 144: 1202-18.
5. Rosenfeld M, Pepe MS, Longton G, Emerson J, FitzSimmons S, Morgan W. Effect of choice of reference equation on analysis of pulmonary function in cystic fibrosis patients. Pediatr Pulmonol. 2001; 31: 227-37.
6. Subbarao P, Lebecque P, Corey M, Coates AL. Comparison of spirometric reference values. Pediatr Pulmonol. 2004; 37: 515-22.
7. Dejsomritrutai W, Nana A, Maranetra KN, et al. Reference spirometric values for healthy lifetime nonsmokers in Thailand. J Med Assoc Thai. 2000; 83: 457-66.
8. Pothirat C, Chaiwong W, Phetsuk N, Liwsrisakun C. Misidentification of airflow obstruction: prevalence and clinical significance in an epidemiological study. Int J Chron Obstruct Pulmon Dis. 2015; 10: 535-40.
9. Dejsomritrutai W, Nana A, Chierakul N, et al. Prevalence of bronchial hyperresponsiveness and asthma in the adult population in Thailand. Chest. 2006; 129: 602-9.
10. Thetkathuek A, Yingratanasuk T, Demers PA, Thepaksorn P, Saowakhontha S, Keifer MC. Rubberwood dust and lung function among Thai furniture factory workers. Int J Occup Environ Health. 2010; 16: 69-74.
11. Quanjer PH, Stanojevic S, Cole TJ, et al. Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations. Eur Respir J. 2012; 40: 1324-43.
12. Pereira CA, Duarte AA, Gimenez A, Soares MR. Comparison between reference values for FVC, FEV1, and FEV1/FVC ratio in White adults in Brazil and those suggested by the Global Lung Function Initiative 2012. J Bras Pneumol. 2014; 40: 397-402.
13. Backman H, Lindberg A, Sovijarvi A, Larsson K, Lundback B, Ronmark E. Evaluation of the global lung function initiative 2012 reference values for spirometry in a Swedish population sample. BMC Pulm Med. 2015; 15: 26.
14. Brazzale DJ, Hall GL, Pretto JJ. Effects of adopting the new global lung function initiative 2012 reference equations on the interpretation of spirometry. Respiration. 2013; 86: 183-9.
15. Quanjer PH, Brazzale DJ, Boros PW, Pretto JJ. Implications of adopting the Global Lungs Initiative 2012 all-age reference equations for spirometry. Eur Respir J. 2013; 42: 1046-54.
16. Dejsomritrutai W, Chuaychoo B. Impact of GLI-2012 Spirometric References and Lower Limit of Normal on Prevalence of COPD in Older Urban Thai Persons. J Med Assoc Thai. 2016; 99: 276-81.
17. Embling LA, Zagami D, Sriram KB, Gordon RJ, Sivakumaran P. Effect of changing from the National Health and Nutritional Examination Survey III spirometry reference range to that of the Global Lung Initiative 2012 at Gold Coast Hospital and Health Service. J Thorac Dis. 2016; 8: 3739-43.
18. Miller MR, Hankinson J, Brusasco V, et al. Standardisation of spirometry. Eur Respir J. 2005; 26: 319-38.
19. Altman DG. Practical statistics for medical research: Chapman and Hall; 1991.
20. Ben Saad H, El Attar MN, Hadj Mabrouk K, et al. The recent multi-ethnic global lung initiative 2012 (GLI2012) reference values don't reflect contemporary adult's North African spirometry. Respir Med. 2013; 107: 2000-8.
21. Culver BH. How should the lower limit of the normal range be defined? Respir Care. 2012; 57: 136-45.
22. Cole TJ, Stanojevic S, Stocks J, Coates AL, Hankinson JL, Wade AM. Age- and size-related reference ranges: a case study of spirometry through childhood and adulthood. Stat Med. 2009; 28: 880-98.
23. McHugh ML. Interrater reliability: the kappa statistic. Biochem Med (Zagreb). 2012; 22: 276-82.
24. Hoehler FK. Bias and prevalence effects on kappa viewed in terms of sensitivity and specificity. Journal of Clinical Epidemiology. 2000; 53: 499–503.