Differences between interpretation strategies of lung function tests in alpha-1 antitrypsin deficiency patients

Introduction:In 2021, ERS/ATS published recommendations for pulmonary function tests (PFTs) interpretation.

Aims:To compare ATS/ERS 2005 and ATS/ERS 2021 recommendations on PFTs interpretation in patients with Alpha-1 antitrypsin deficiency (AATD).

Methods:Inclusion of AATD patients followed in a central hospital (2014-2022). Data was collected from the most complete PFTs. Global Lung Function Initiative equations were applied to analyse the agreement between the two PFTs methodologies.

Results:A total of 101 patients were enrolled. Of those with FEV1/FVC ratio <0.70, 8% (n=8) were above the limit of normal (LN) at the 5th percentile (Cohen?s kappa (k)=84%). Regarding obstruction severity, 63% (n=10) of moderate/moderate-severe obstruction were classified as mild; and 68%(n=19) of severe/very severe were classified as moderate according to ATS/ERS 2021 (k=49%).

For TLC, we found an almost perfect concordance(k=95%). For RV, 19 (31%) of the cases classified as increased, were between LNs (k= 57%).

For DLCO, 21% (n=4) of the patients with mild impairment changed for moderate, and 20% (n=4) with moderate were severe when analysed by LN (k=88%).

Conclusion:Agreement between methodologies was almost perfect in TLC, sufficient in obstruction definition and DLCO impairment severity, and moderate in other variables. Obstruction degree seems to be underestimated and fewer patients will have air trapping with the new classification, although DLCO will be more sensitive to severe cases. Integration with clinical information is fundamental.