Pre-operative evaluation of lung function test results

To the Editors:

The European Respiratory Society/European Society of Thoracic Surgeons joint clinical guidelines on fitness for radical therapy in lung cancer patients (surgery and chemo-radiotherapy) were published in the July 2009 issue of the European Respiratory Journal 1. This comprehensive and very important document provides guidelines for the risk evaluation of candidates for lung cancer surgery. We fully agree that the lung function variables forced expiratory volume in 1 s (FEV₁) and diffusing capacity of the lung for carbon monoxide (D_L,CO), together with exercise capacity, are essential components in the risk stratification. We do not, however, agree on the recommended interpretation and evaluation of the test results. In the guidelines, lung function results are evaluated as customary in terms of percent of predicted normal values, i.e. corrected for sex, age, height and, for some variables, also weight (exercise test) 1. In our opinion, the correction for age is inappropriate when estimating peri-operative risk. This is because expressing lung function results in percent of predicted normal values results in ignorance of the normal age-related decline in lung function and exercise capacity. The guidelines recommend a post-operative predicted FEV₁ value of 30% predicted to be a high-risk threshold. 30% pred normal FEV₁ for a 70-yr-old male with a height of 178 cm is 0.9 L compared with 1.3 L for a male of the same height aged 25 yrs 2. Thus, according to the recommendations, the high-risk threshold regarding FEV₁ is 0.9 L for a 70-yr-old patient but 1.3 L for the 25 yr old! There are of course similar consequences regarding D_L,CO and exercise capacity.

One of several possible ways to deal with this problem is to express results of lung function tests and exercise tests of adults as percent of predicted normal at age 25 yrs (% pred_25yrs) irrespective of the actual age. In the example above regarding the 70-yr-old patient, the guideline recommended high-risk threshold of post-operative predicted 30% pred corresponds to 0.9 L, which is equivalent to a post-operative predicted value of ∼20% pred_25yrs. Thus, we suggest the high-risk threshold to be 20% pred_25yrs for FEV₁, D_L,CO and exercise capacity.

Statement of interest

None declared.