Plot of HSE 2011 FEV1/FVC Males

GOLD v LLN    Page 3

How does GOLD define the presence of airflow limitation?

   GOLD applies a value of 0.7 for the value of FEV1/FVC to define airflow limitation. Over 50 published prediction equations for FEV1/FVC have found that this ratio falls with age [13] and so the LLN for this index also drops with age. The only publication cited by GOLD to substantiate their use of a 0.7 cut off [15] also found the ratio fell with age in women but not to a significant extent in men. This was largely because they had not adequately sampled elderly men.

The Figure at the top shows the results for FEV1/FVC in men from the Health Survey of England data for 2011[7]. All the subjects plotted as pale grey dots are truly within the normal range. Those plotted in black dots are below the LLN from the GLI-2012 equations [14]. The yellow dots are those subjects where GOLD falsely says they are normal (>0.70) but are in fact below the LLN (false negatives) and the green dots are those where GOLD says they are abnormal when in fact they are above the LLN (false positives).

   Plot of HSE 2011 FEV1/FVC FemalesWhen considering a similar plot for females in the Figure to the right it can be seen that the age at which the 0.7 cutoff changes from giving false negatives (yellow) to false positives (green) in women is about 50 yrs and is older than that found in men, approx 40 yrs.

   Therefore the GOLD criterion of FEV1/FVC<0.7 for defining airflow limitation not only falsely categorises subjects it also introduces a sex bias.