Spirometric variability in smokers: transitions in COPD diagnosis in a five-year longitudinal study

Respiratory Research

Table 4 Summary of Beneficial Transition Probabilities for Spirometrically-defined States at Any Time Over Approximately 5 Years, Albuquerque, New Mexico, 2001–2015, Lovelace Smokers’ Cohort

	Normal spirometry at any time	COPD GOLD Stage I at any time	GOLD Unclassified at any time	COPD GOLD Stage II+ at any time
All smokers, irrespective of spirometric disease at baseline (n = 1553)
All beneficial transitions^a	87 %	16 %	39 %	22 %
Resolution of disease^a	NA	16 %	35 %	4 %
Smokers with normal spirometry at baseline (n = 956)*
All beneficial transitions^a	89 %	26 %	64 %	64 %
Resolution of disease^a	NA	26 %	57 %	29 %
Smokers with abnormal spirometry at baseline (n = 597)
All beneficial transitions^a	55 %	12 %	33 %	20 %
Resolution of disease^a	NA	12 %	29 %	2 %

Abbreviations COPD Chronic Obstructive Pulmonary Disease, GOLD Global Initiative for Chronic Obstructive Lung Disease
^aA beneficial transition, our primary outcome variable, was defined by either a decrease in spirometric state severity, including resolution, or continued maintenance of normal spirometric state at any time during longitudinal follow-up. Resolution of disease state, our secondary outcome variable, was defined by change of spirometrically-defined diseased states to normal spirometry state at any time during longitudinal follow-up
*reflect transitions for new onset disease
Additional data are provided in Fig. 1 in the main text and Additional file 1: Figures SE1 and SE2, including data on change in severity of individual spirometric disease states
Probabilities for beneficial transition and for resolution of disease were significantly different between groups with ‘normal’ and ‘abnormal spirometry at baseline’ (P < 0.001 for both analyses), using SAS Proc GENMOD
A similar table using the statistically defined NHANES-III lower limits of normal for FEV₁/FVC ratio to define obstruction is presented in the Additional file 1: Table SE2

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