Preliminary Study On Spirometric Reference Equations For Elderly Chinese In Jinan

BackgroundThe interpretation of spirometry depends on the comparison between observed values and predicted values which vary on different ethnicity,sex,age,height,and weight.Different reference values lead to different interpretation even for the same individual.As the susceptible population of chronic respiratory disease,the elderly has unique respiratory physiological characteristics.Making correct decision on spirometry of the elderly with appropriate reference values is of great significance for the prevention,diagnosis,and treatment of respiratory diseases.At present,there are numerous published lung function reference equations for Chinese populations,but these frequently include low proportions of elderly people,and few of them focus on the elderly.This study aims to validate the applicability of published predicted values for spirometry to the elderly,and to develop reference equations for elderly Chinese in Jinan.The study was divided into two parts.Part One:Applicability of Global Lung Function Initiative 2012 reference equations for spirometry to elderly Chinese in JinanObjectiveTo validate the applicability of Global Lung Function Initiative 2012 reference values for spirometry to elderly Chinese in Jinan.MethodsWe recruited healthy never-smokers aged 60-84 to take spirometry.FVC(forced vital capacity),FEV1(forced expiratory volume in 1 second),FEV1/FVC were recorded.Z-scores were computed using the GLI-2012 reference values.Comparisons of GLI-2012 predicted values and observed values,lower limit of’ normal(LLN)computed using GLI-2012 and Zhongshan-2011 equations were performed by paired t test.Results1.438 subjects(228 females,210 males)were completely qualified.2.The Z-scores of FVC,FEV1 and FEVi/FVC for males were,respectively,0.23± 1.34,0.27± 1.31,0.03±0.71;for females were 0.22±0.95,0.08±0.89,-0.28±0.65.3.The predicted mean values of GLI-2012 were in good agreement with observed values.However,the LLN of FEV1/FVC predicted by GLI-2012 equations were lower than that of Zhongshan-201 1.The 95%confidence interval of mean difference for males was[-5.79,-5.55]%(t=-91.310,,P<0.001).The proportion of abnormal FEV1/FVC in the sample was 0.9%(4/438)in terms of the GLI-2012 LLN,which was similar to the proportion when using x-3s as the cut off value(0.7%,3/438).ConclusionsThe GLI-2012 predicted mean values for spirometry were appropriate for the elderly in Jinan,but it underestimated the LLN of FEV1/FVC and may lead to the missed diagnosis of obstructive ventilatory defects.Part Two:Spirometric reference equations for elderly Chinese in Jinan aged 60-84 yearsObjectivesThis part aimed at developing spirometric reference equations for elderly Chinese in Jinan aged 60-84 years and to compare them to previous equations.MethodsThe project covered all of Jinan city and the recruitment period lasted 9 months from January 1,2017 to September 30,2017,434 healthy people who had never smoked(226 females,208 males)aged 60-84 years were recruited to undergo spirometry.Vital capacity(VC),forced vital capacity(FVC),forced expiratory volume in 1 second(FEV1),FEV1/FVC,FEV1/VC,forced expiratory volume in 6 seconds(FEV6),peak expiratory flow(PEF),forced expiratory flow at 25%,50%,75%,and 25%-75%of FVC exhaled(FEF25%,FEF50%,FEF75%,FEF25%-75%)were analyzed.Reference equations for mean and the lower limit of normal(LLN)were derived using the LMS method.Comparisons between new and previous equations were performed by paired t-test.Results1.New reference equations were developed from the sample.2.The LLN of FEV1/FVC,FEF25%-75%computed using the 2012-GLI(Global Lung Function Initiative)equations were lower than the new equations.The biggest degree of difference for FEV1/FVC was 6%(70.46%vs.59.29%,t = 62.241,P<0.001),for FEF25%-75%,it was 5%(0.82 vs.0.77,t = 16.861,P<0.001).3.The 1990-North China,2009-North China equations predicted higher mean values of FEV1/FVC and FEF25%-75%than the present model.The biggest degrees of difference were,respectively,-4%(78.31%vs.81.27%,t =-85.359,P<0.001),-60%(2.11 vs.4.68,t =-170.287,P<0.001).ConclusionsThe newly developed spirometric reference equations are applicable to elderly Chinese in Jinan.The 2012-GLI equations may lead to missed diagnoses of obstructive ventilatory defects and the small airway dysfunction while traditional linear equations for all ages may lead to overdiagnosis.