Table 2.

Design of the study

	Time (weeks)	Examination of slides	Description
Phase 1	2	Pairwise (2 × 24 slides)	Matched asthma and COPD slides were offered pairwise. The pathologists were informed about this and could only opt for asthma or COPD, thus chose for two options per pair. Once chosen, the pathologists were not able to change their choice or go back to slides shown earlier.
Interval	4–6
Phase 2	4	Randomly mixed (48 slides)	The 48 slides were randomly mixed. The pathologists were informed about this and had to opt for asthma or COPD per slide. Once chosen, the pathologists were not able to change their choice or go back to slides shown earlier.
Interval	4–6
Phase 3a	2	Randomly mixed + criterion list (48 slides)	Conform phase 2. Additionally, the pathologists were asked per slide to score for the presence or absence of a criterion that drove their diagnosis (Box 1). After scoring the criterion list they had to choose for asthma or COPD and to give their level of certainty (VAS 0–10).
Interval	4–6
Phase 3b	2	Randomly mixed + criterion list (24 slides)	Conform phase 3a. This phase aimed to test repeatability.
Interval	4–6
Phase 4	2	Pairwise (2 × 24 slides)	Conform phase 1. This phase aimed to test repeatability (and/or potential learning effects).
	Totally 28–36 weeks