Table 2. Expertise levels and experience of the human observers.

	Job Title	Expertise levela	Reading chest CTb (years)
Observer 1	MD researcher	I	0
Observer 2	MD researcher	I	2
Observer 3	Junior resident	II	2
Observer 4	Junior resident	II	2
Observer 5	Clinical research coordinator	II	7
Observer 6	Senior resident	IV	8
Observer 7	Senior radiologist	V	34
Observer 8	Chest radiologist	V	10

^alevel of expertise based as on Reference [24]: I has knowledge and some skills, II acts under full supervision, III acts under limited supervision, IV acts without supervision, V supervises and teaches;

^bYears since the observer started reading and evaluating chest CT scans; Observer 1 to 5 were considered ‘less experienced observers’ and observer 6 to 8 were considered ‘experienced observers’.