DOI: 10.36347/sjams.2018.v06i09.038

Pages: 3421-3431

Spirometry is the most important method of investigation in respiratory medicine. When conducting Spirometry, South Indians’ references were mostly used as prediction values for Sri Lankans. There can be some misinterpretations of lung function test results when using Indian references for Sri Lankan individuals. Hence, objectives of this study were to develop separate prediction equations, and investigate reference values for Spirometry for healthy Sri Lankan adults’ of age between 20 to 65 years and compare these values with reference values which obtained using South Indian references of Sri Lankan individuals. Healthy nonsmoking individuals were selected as the study sample and the sample size was 1021 subjects including 520 (50.9%) males and 501(49.1%) females. Data collection was categorized to 20-25, 26-35, 36-45, 46-55, 56-65 years of age groups to make the data collection more reliable. Prediction equations for Forced Vital Capacity (FVC), Force Expiratory volume within first second (FEV1), FEV1/FVC%, Peak Expiratory Flow Rate (PEFR) were derived using each individuals’ age, standing height, weight and BMI for both male and females separately and Lower Limits of Normal (LLN) were calculated to clarify the level of diagnosing of a disease condition. GAMLSS model with Box-Cox-Cole-Green (BCCG) family distribution was selected as the best fitted model to derive prediction equations and prediction values were generated using those equations. When compare these prediction values, FVC, FEV1 and PEFR values were overestimated while FEV1/FVC% was underestimated by reference values which obtained using South Indian references of Sri Lankan individuals for both males and females and there is significant difference between reference values which obtained using South Indian references and Sri Lankan references of Sri Lankan individuals at 5% significant level. Hence, this study is concluded that separate reference values can be used for Sri Lankan individuals when cond