Researchers from the University Medical Center Groningen performed a validation of the Pulmonary Function Test from participants at 1A visit 1 and 2A visit 1 (sections: physical state (Pulmonary Function Test) and secondary & linked variables).

The gender index can be requested in the Lifelines catalogue or by mail (data@lifelines.nl).

Spirometry is performed according to Standard Operating Procedures using the WEllch Allyn SpiroPerfect device. Judgment on technical correctness is performed by a Lifelines assistant, a pulmonologist, or both, according to a standard review procedure. Only data from pulmonary function tests that are judged to be technically correct should be used in the analyses. Technically correct is defined as:

• Test performed according to ATS criteria or
• Test not performed according to ATS criteria, but clinically reliable.

In case both the pulmonologist and the Lifelines assistant judged the technical correctness, the priority is given to the judgment of the pulmonologist.

To select only technically valid measurements the following rules were applied:

Reference values based on age, height, and sex are calculated based on the Global Lung Function Initiative (GLI) using the GLI provided syntax codes and databases.

• It is important to note that ethnicity has not been taken into account. Everyone has been treated as Caucasian.
• There are a few adults subjects with a huge difference in height between 1A visit 1 and 2A visit 1 resulting in a huge difference in reference values. It is recommended to exclude the adult subjects with a height difference of more than 5 cm using the height variable.