Defining obstructive ventilatory defect in 2015
Introduction: There is no clear consensus as to what constitutes an obstructive ventilatory defect (OVD): Is it FEV1/FVC<lower limit of normal (LLN) or <0.70 (respectively, physiological and operational definitions)? Aim: To determine, according to the two definitions, the percentage of subjects having an OVD among them explored in a lung function exploration laboratory.
Population and methods: This is a retrospective study including 4,730 subjects aged 17-85 years. Subjects were divided according to the presence [physio (+) or operat (+)] or absence [physio (-) or operat (-)] of an OVD, and into younger (<45 years, n=2,076), older (>45 years, n=2,654), smokers (n=1,208), and non-smokers (n=3,522) groups.
Results: For the total sample, the younger and older groups [mean+SD of age (years), respectively, 46.7+14.1; 33.9+7.4, and 56.8+9.1], the ‘physiological definition’ detected, respectively, 13.46, 43.22, and 5.09% more OVD than the ‘operational one’ (p<0.05). In addition, the operational definition, compared with the physiological one, overdiagnosed OVD in 2.33 and 0.44% of smokers and non-smokers, respectively, and underdiagnosed it in 4.46% and 29.72% of smokers and non-smokers, respectively (p<0.05). Compared with the group ‘physio (-), operat (+)’, the ‘physio (+), operat (-)’ one was younger (74.2+4.7 years vs. 40.9+10.3 years) and had significantly higher FEV1 (62+13% vs. 78+17%) and FVC (71+15% vs. 93+19%).
Conclusion: The frequency of OVD much depends on the criteria used for its definition.
Keywords: obstructive ventilatory defect; FEV1/FVC; fixed threshold; lower limit of normal; spirometry; guideline