Spirometry and "restrictive pattern"
In 1991 an ATS-committee suggested that it was possible to uncover a restrictive ventilatory defect, i.e. a condition in which the total lung capacity is reduced, on the basis of an abnormally low VC in combination with a normal or high FEV1/FVC ratio: “restrictive pattern” . Since then a restrictive pattern has been regularly described in the literature, suggesting that it is considered a clinically meaningful pattern. The prevalence rate in an Australian and Polish population of hospital patients varied with age between 5 and 20% (see figure); the number of observations above age 80 year was very limited, so that the pattern above that age should be neglected. Differences in the prevalence rate according to the three sets of prediction equations are considerable. The general pattern is that adopting the GLI-2012 equations leads to an increase in the prevalence rate of a restrictive pattern compared to ECCS/ERS. This is worrisome, as it may lead to an increase in requests to measure the total lung capacity, leading to an increase in medical expenditure. It is known that this spirometric pattern has a low sensitivity for correctly diagnosing restrictive lung disease: 50% or less in a clinical population [2-4]. Lung restriction is rare in the general population, so that it is best if general practitioners ignore a restrictive pattern. In fact, in general it is better to ignore this pattern, unless there is clinical evidence compatible with lung restriction (lung resection, severe kyphoscoliosis, etc.) and documenting such a defect is clinically relevant. The general idea should be: “treat the patient, not the numbers”.
|Percentage of patients with airway obstruction (FEV1/FVC < LLN) based on GLI-2012  predicted values, or with GOLD stage 2-4.|
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Acknowledgement: Illustrations modified and reproduced with permission of the European Respiratory Society. Eur Respir J 2013; in press; doi: 10.1183/09031936.00195512.