Background: Spirometric reference values vary substantially across ethnic groups, and remain largely poorly characterized among Africans. We derived spirometric reference equations for adult Cameroonians and compared their performance with those derived from other ethnic groups. Methods: Spirometric variables according to the American Thoracic Society/European Respiratory Society 2005 guidelines were acquired in voluntary healthy non-smoker subjects in Yaounde (Capital City) and Foumbot (semi-urban area in West Region), in Cameroon during November 2011 to January 2012 (Yaounde) and August 2012 (Foumbot). Reference equations were derived separately for men and women from multiple linear regressions. Results: A total of 411 subjects (206 men) met the inclusion criteria. The mean age was 39.5 ± 16.1 years (min - max: 18 - 85 years) for men and 39.2 ± 14.1 years (18 - 90 years) for women. Age and height were the only variables significantly associated with spirometric values in the final linear regression models. Derived reference values were lower than those derived from Global Lung Initiative 2012 equations for different ethnic groups, except for the forced expiratory volume in 1 second/forced vital capacity ratio (FEV1/FVC ratio). The mean FEV1/FVC ratio was 0.88 ± 0.07 for Cameroonian men and 0.89 ± 0.07 for Cameroonian women. Variations in the performance of derived models in bootstrap internal validation were marginal. Conclusion: This study highlights the importance of deriving specific predictive equations for each ethnic group. The use of adjustment factors applied to Caucasian equations when compared with the values derived in our study leads to an overestimation of the values for FEV1 and FVC.
References
[1]
M. R. Miller, J. Hankinson, V. Brusasco, F. Burgos, R. Casaburi, A. Coates, R. Crapo, P. Enright, C. P. van der Grinten, P. Gustafsson, R. Jensen, D. C. Johnson, N. MacIntyre, R. McKay, D. Navajas, O. F. Pedersen, R. Pellegrino, G. Viegi and J. Wanger, “Standardisation of Spirometry,” European Respiratory Journal, Vol. 26, No. 2, 2005, pp. 319-338.
http://dx.doi.org/10.1183/09031936.05.00034805
[2]
“Lung Function Testing: Selection of Reference Values and Interpretative Strategies. American Thoracic Society,” American Review of Respiratory Disease, Vol. 144, No. 5, 1991, pp. 1202-1218.
http://dx.doi.org/10.1164/ajrccm/144.5.1202
[3]
P. H. Quanjer, G. J. Tammeling, J. E. Cotes, O. F. Pedersen, R. Peslin and J. C. Yernault, “Lung Volumes and Forced Ventilatory Flows. Report Working Party Standardization of Lung Function Tests, European Community for Steel and Coal. Official Statement of the European Respiratory Society,” European Respiratory Journal Supplement, Vol. 16, 1993, pp. 5-40.
[4]
S. Stanojevic, A. Wade and J. Stocks, “Reference Values for Lung Function: Past, Present and Future,” European Respiratory Journal, Vol. 36, No. 1, 2010, pp. 12-19.
http://dx.doi.org/10.1183/09031936.00143209
[5]
M. Oscherwitz, S. A. Edlavitch, T. R. Baker and T. Jarboe, “Differences in Pulmonary Functions in Various Racial Groups,” American Journal of Epidemiology, Vol. 96, No. 5, 1972, pp. 319-327.
[6]
N. L. Lapp, H. E. Amandus, R. Hall and W. K. Morgan, “Lung Volumes and Flow Rates in Black and White Subjects,” Thorax, Vol. 29, No. 2, 1974, pp. 185-188.
http://dx.doi.org/10.1136/thx.29.2.185
[7]
A. Fulambarker, A. S. Copur, A. Javeri, S. Jere and M. E. Cohen, “Reference Values for Pulmonary Function in Asian Indians Living in the United States,” Chest, Vol. 126, No. 4, 2004, pp. 1225-1233.
http://dx.doi.org/10.1378/chest.126.4.1225
[8]
B. Korotzer, S. Ong and J. E. Hansen, “Ethnic Differences in Pulmonary Function in Healthy Nonsmoking Asian-Americans and European-Americans,” American Journal of Respiratory and Critical Care Medicine, Vol. 161, No. 4, 2000, pp. 1101-1108.
http://dx.doi.org/10.1164/ajrccm.161.4.9902063
[9]
P. H. Quanjer, S. Stanojevic, T. J. Cole, X. Baur, G. L. Hall, B. H. Culver, P. L. Enright, J. L. Hankinson, M. S. Ip, J. Zheng and J. Stocks, “Multi-Ethnic Reference Values for Spirometry for the 3-95-yr Age Range: The Global Lung Function 2012 Equations,” European Respiratory Journal, Vol. 40, No. 6, 2012, pp. 1324-1343.
http://dx.doi.org/10.1183/09031936.00080312
[10]
F. Boutros-Toni, B. Pigearias, P. Konate and J. Lonsdor- fer, “Spirometric Reference Values in Black Females,” Bulletin Européen de Physiopathologie Respiratoire, Vol. 19, No. 4, 1983, pp. 331-338.
[11]
P. Dufetel, B. Pigearias, J. Lonsdorfer, G. Derossi, C. Diaine and P. J. Faltot, “Spirometric Reference Values in Senegalese Black Adults,” European Respiratory Journal, Vol. 2, No. 4, 1989, pp. 352-358.
[12]
S. J. Louw, J. G. Goldin and G. Joubert, “Spirometry of Healthy Adult South African Men. Part I. Normative Values,” South African Medical Journal, Vol. 86, No. 7, 1996, pp. 814-819.
[13]
Y. A. Mengesha and Y. Mekonnen, “Spirometric Lung Function Tests in Normal Non-Smoking Ethiopian Men and Women,” Thorax, Vol. 40, No. 6, 1985, pp. 465-468.
http://dx.doi.org/10.1136/thx.40.6.465
[14]
E. Hnizdo, G. Churchyard and R. Dowdeswel, “Lung Function Prediction Equations Derived from Healthy South African Gold Miners,” Occupational and Environemental Medicine, Vol. 57, No. 10, 2000, pp. 698-705.
[15]
T. M. Knudsen, O. Morkve, S. Mfinanga and J. A. Hardie, “Predictive Equations for Spirometric Reference Values in a Healthy Adult Suburban Population in Tanzania,” Tanzania Journal of Health Research, Vol. 13, No. 3, 2011, pp. 1-10.
http://dx.doi.org/10.4314/thrb.v13i3.64540
[16]
B. G. Ferris, “Epidemiology Standardization Project (American Thoracic Society),” American Review of Respiratory Disease, Vol. 118, No. 6, 1978, pp. 1-120.
[17]
“Calcul de la Surface Corporelle et du Poids Maigre,” 2011. http://www.aly-abbara.com/echographie/biometrie/surface_corporelle_ccreatinine_eau_poids.html
[18]
“Standardization of Spirometry, 1994 Update. American Thoracic Society,” American Journal of Respiratory and Critical Care Medicine, Vol. 152, No. 3, 1995, pp. 1107- 1136. http://dx.doi.org/10.1164/ajrccm.152.3.7663792
[19]
F. E. Harrell, “Regression Modeling Strategies,” Springer-Verlag, New York, 2001.
http://dx.doi.org/10.1007/978-1-4757-3462-1
[20]
W. Van Ganse, L. Billet and B. Ferris, “Medical Criteria for the Selection of Normal Subject,” In P. Arcangeli, J. E. Cotes and A. Cournand, Eds., Introduction to the Definition of Normal Values for Respiratory Function in Man, Panminerva Medica, Alghero, 1969.
[21]
P. H. Quanjer, J. Stocks, T. J. Cole, G. L. Hall and S. Stanojevic, “Influence of Secular Trends and Sample Size on Reference Equations for Lung Function Tests,” European Respiratory Journal, Vol. 37, No. 3, 2011, pp. 658-664. http://dx.doi.org/10.1183/09031936.00110010
[22]
M. R. Miller, P. H. Quanjer, M. P. Swanney, G. Ruppel and P. L. Enright, “Interpreting Lung Function Data Using 80% Predicted and Fixed Thresholds Misclassifies More than 20% of Patients,” Chest, Vol. 139, No. 1, 2011, pp. 52-59. http://dx.doi.org/10.1378/chest.10-0189
[23]
S. Mukhopadhvay, K. A. Macleod, T. J. Ong and S. A. Ogston, “‘Ethnic’ Variation in Childhood Lung Function May Relate to Preventable Nutritional Deficiency,” Acta Paediatrica, Vol. 90, No. 11, 2001, pp. 1299-1303.
http://dx.doi.org/10.1111/j.1651-2227.2001.tb01579.x
[24]
M. Golshan, M. Nematbakhsh, B. Amra and R. O. Crapo, “Spirometric Reference Values in a Large Middle Eastern Population,” European Respiratory Journal, Vol. 22, No. 3, 2003, pp. 529-534.
http://dx.doi.org/10.1183/09031936.03.00003603
