@article {Vaz Fragoso1771, author = {Carlos A Vaz Fragoso and Thomas M Gill and Gail McAvay and Peter H Van Ness and H Klar Yaggi and John Concato}, title = {Use of Lambda-Mu-Sigma-Derived Z Score for Evaluating Respiratory Impairment in Middle-Aged Persons}, volume = {56}, number = {11}, pages = {1771--1777}, year = {2011}, doi = {10.4187/respcare.01192}, publisher = {Respiratory Care}, abstract = {BACKGROUND: The lambda-mu-sigma (LMS) method calculates the lower limit of normal for spirometric values as the 5th percentile of the distribution of Z scores. Conceptually, LMS-derived Z scores account for normal age-related changes in pulmonary function, including variability and skewness in reference data. Evidence is limited, however, on whether the LMS method is valid for evaluating respiratory impairment in middle-aged persons. OBJECTIVE: To evaluate the association of LMS-defined respiratory impairment (airflow limitation and restrictive pattern) with mortality and respiratory symptoms. METHODS: We analyzed spirometric data from white participants ages 45{\textendash}64 years in the Third National Health and Nutrition Examination Survey (NHANES III, n = 1,569) and the Atherosclerosis Risk in Communities study (ARIC, n = 8,163). RESULTS: LMS-defined airflow limitation was significantly associated with mortality (adjusted hazard ratios: NHANES III 1.90, 95\% CI 1.32{\textendash}2.72, ARIC 1.28, 95\% CI 1.06{\textendash}1.57), and respiratory symptoms (adjusted odds ratios: NHANES III 2.48, 95\% CI 1.75{\textendash}3.51, ARIC 2.27, 95\% CI 1.98{\textendash}2.62). LMS-defined restrictive-pattern was also significantly associated with mortality (adjusted hazard ratios: NHANES III 1.98, 95\% CI 1.08{\textendash}3.65, ARIC 1.38, 95\% CI 1.03{\textendash}1.85), and respiratory symptoms (adjusted odds ratios: NHANES III 2.34, 95\% CI 1.44{\textendash}3.80, ARIC 1.89, 95\% CI 1.46{\textendash}2.45). CONCLUSIONS: In white middle-age persons, LMS-defined airflow limitation and restrictive-pattern were significantly associated with mortality and respiratory symptoms. Consequently, an approach that reports spirometric values based on LMS-derived Z scores might provide an age-appropriate and clinically valid strategy for evaluating respiratory impairment.}, issn = {0020-1324}, URL = {https://rc.rcjournal.com/content/56/11/1771}, eprint = {https://rc.rcjournal.com/content/56/11/1771.full.pdf}, journal = {Respiratory Care} }