Pulmonary Rehabilitation |

Using the Lower Limit of Normal (LLN) for the FEV1/FVC Ratio Changes the Prevalence of Airway Obstruction in a Hospital Based-Population FREE TO VIEW

Vanina Martín, MD; Marcela Heres, MD; Sebastian Lamot, MD; Marco Solis, MD; Nicolas Itcovici, MD; Silvia Quadrelli, MD
Author and Funding Information

Fundación Sanatorio Guemes, Ciudad Autónoma de Buenos Aires, Argentina

Chest. 2013;144(4_MeetingAbstracts):826A. doi:10.1378/chest.1704136
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SESSION TITLE: Physiology/PFTs/Rehabilitation Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM

PURPOSE: Published guidelines recommend spirometry to accurately diagnose COPD. However, even spirometry-based COPD prevalence estimates can vary widely. GOLD recommendations define COPD as a post-bronchodilator FEV/FVC of <70%, with the severity based on the value of FEV1. However, there is currently no consensus on the criteria for diagnosing COPD. This study evaluated the impact of different definitions of airway obstruction on the estimated prevalence of obstruction in a hospital-based sample.

METHODS: All consecutive spirometry tests performed in adult subjects at the pulmonary function laboratory of a tertiary reference center from January 2011 to December 2012. Obstructive airway disease was defined using the following criteria: 1)self-reported diagnosis of chronic bronchitis or emphysema; 2)FEV1/FVC<0.70; 3)FEV1/FVC<0.70 and FEV1<80% predicted (GOLD Stage IIA); 4)FEV1/FVC<0.88 (ERS 95); 5) FEV1/FVC below the LLN (ECCS/ERS reference values). This analysis was performed using the ECCS/ERS prediction equation. All analyses were performed using SPSS 14.0 for Windows (SPSS, Chicago, Illinois, USA).

RESULTS: 3567 subjects that performed an eligible spirometry (1716 men, age 51,5±16,6 year-old, FVC 90,6±18,4%, FEV1 81,2±20,1%, FEV1/FVC 71,1±11,4%). Rates in studied patients varied from 1) 15,9 % (self-report), 2) 37,1% in GOLD fixed FEV1/FVC ratio below 70%, 3) 27,7% in GOLD stage II (FEV1/FVC<70% + FEV1<80%), 4) 69% (fixed ratio< 88% using ERS equation) and 5) 28% (FEV1/FVC below the LLN). For persons aged >50 yrs, the fixed ratio criteria produced the highest rate estimates. For all subgroups tested, the GOLD Stage II criteria produced lower estimates than other spirometry-based definitions.

CONCLUSIONS: This study demonstrates that in the daily practice of a pulmonary function laboratory, large differences in the prevalence of obstruction exist when defined by spirometry that arise from using different definitions even using the same prediction equations. While a fixed cut-off seems easy to apply, it comes at the expense of erroneous classification of disease.

CLINICAL IMPLICATIONS: A clear definition of COPD that can serve as a guide to clinicians is still not available.

DISCLOSURE: The following authors have nothing to disclose: Vanina Martín, Marcela Heres, Sebastian Lamot, Marco Solis, Nicolas Itcovici, Silvia Quadrelli

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