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The "lower limit of normal" for spirometry once more

There can be little doubt that the distribution of lung function indices of healthy subjects and those with lung pathology overlaps. It is therefore risky to conclude that a test result > lower limit of normal (5th percentile) excludes pathology; it goes without saying that clinical judgement matters. On that account it has been suggested that a FEV1/FVC ratio < 0.70 but > lower limit of normal, hence within the normal range and dubbed the “twilight zone”, represents lung pathology. Evidence to support this is lacking. However, if subjects in the “twilight zone” develop respiratory symptoms and signs after a number of years, this might lend support to this claim. Supportive evidence has not been found in longitudinal studies:

Do not apply the GOLD criterion for airway obstructionGOLD stage 1 (FEV1/FVC < 0.70 & FEV1 > 80% predicted) in asymptomatic subjects is not associated with
• Premature death [1-5]
• Accelerated decline in FEV1, development of respiratory symptoms, increased use of health care, decrease in “quality of life” [6,7].

FEV1/FVC < lower limit of normal is associated with
• Premature death [8,9]
• Development of respiratory symptoms [10].

Use the lower limit of normal for diagnosing airway obstructionConclusion: The GOLD criterion is unscientific, clinically unfounded, and the use of FEV1/FVC < 0.70 as a criterion for diagnosing airway obstruction should be discouraged in view of under diagnosis in young subjects and extensive over diagnosis in elder adults [11]; use the lower limit of normal (LLN) instead.


  1. Ekberg-Aronsson M, Pehrsson K, Nilsson JA, Nilsson PM, Löfdahl CG. Mortality in GOLD stages of COPD and its dependence on symptoms of chronic bronchitis. Respir Res 2005; 6: 98. Manuscript
  2. Vaz Fragoso CA, Concato J, McAvay G, et al. Chronic obstructive pulmonary disease in older persons: a comparison of two spirometric definitions. Respir Med 2010; 104: 1189 - 1196. PubMed
  3. Pedone C, Scarlata S, Sorino C, Forastiere F, Bellia V, Antonelli Incalzi R. Does mild COPD affect prognosis in the elderly? BMC Pulm Med 2010; 10: 35. Manuscript
  4. Mannino DM, Doherty DE, Buist AS. Global Initiative on Obstructive Lung Disease (GOLD) classification of lung disease and mortality: findings from the Atherosclerosis Risk in Communities (ARIC) study. Respir Med 2006; 100: 115–122. PubMed
  5. Vaz Fragoso C, Gill T, McAvay G, et al. Use of lambda-mu-sigma-derived Z score for evaluating respiratory impairment in middle-aged persons. Respir Care 2011; 56: 1771-1777. Manuscript
  6. Bridevaux P-O, Gerbase MW, Probst-Hensch NM, Schindler C, Gaspoz JM, Rochat T. Long-term decline in lung function, utilisation of care and quality of life in modified GOLD stage 1 COPD. Thorax 2008; 63: 768 - 774. Manuscript
  7. Akkermans R, Biermans M, Robberts B et al. COPD prognosis in relation to diagnostic criteria for airflow obstruction in smokers. Eur Respir J 2013 published ahead of print as doi: 10.1183/09031936.00158212.
  8. Vaz Fragoso CA, Concato J, McAvay G, et al. Chronic obstructive pulmonary disease in older persons: a comparison of two spirometric definitions. Respir Med 2010; 104: 1189 - 1196. Abstract
  9. Mannino DM, Buist AS, Vollmer WM. Chronic obstructive pulmonary disease in the older adult: what defines abnormal lung function? Thorax 2007; 62: 37–241. Manuscript
  10. Vaz Fragoso CA, Concato J, McAvay G, et al. The ratio of FEV1 to FVC as a basis for establishing chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2010; 181: 446 - 451. Manuscript
  11. Quanjer PH, Enright PL, Miller MR, et al. Open Letter. The need to change the method for defining mild airway obstruction. Eur Respir J 2011; 37: 720-722. Manuscript


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