Table 4: Differential item functioning (DIF). Only significant results are shown.

ScaleItemAsthmaticsDepressivesSomatisers
partial 𝛾   coefficient

Chemical int.item 2 (tobacco smoke)0.17 (se = 0.06)−0.16 (se = 0.06)
item 4 (gasoline)−0.23 (se = 0.06)
item 8 (tar)0.16 (se = 0.04)−0.17 (se = 0.06)

Life Impactitem 2 (work ability)0.14 (se = 0.06)
item 4 (choice of clothing)−0.31 (se = 0.12)
item 6 (choice of products)−0.16 (se = 0.08)
item 8 (choice of hobbies)0.20 (se = 0.09)
item 9 (relation with spouse)−0.19 (se = 0.10)

Symptom severityitem 1 (muscle and joint pain)0.23 (se = 0.06)−0.19 (se = 0.06)
item 2 (mucosal or respiratory)0.47 (se = 0.04)−0.30 (se = 0.07)
item 4 (stomach and digestive)−0.17 (se = 0.07)
item 5 (concentration/memory)−0.16 (se = 0.06)0.36 (se = 0.06)
item 6 (tension and nervousness)−0.15 (se = 0.07)0.79 (se = 0.04)
item 7 (balance or coordination)0.21 (se = 0.07)0.24 (se = 0.08)
item 10 (genital and urinary)−0.20 (se = 0.06)−0.27 (se = 0.08)

Other Int.item 3 (unusual cravings)−0.33 (se = 0.06)
item 4 (feeling ill after meals)0.42 (se = 0.08)0.39 (se = 0.07)
item 6 (feeling ill)−0.21 (se = 0.08)0.24 (se = 0.09)
item 7 (alcoholic drinks)0.27 (se = 0.09)
item 10 (allergic reactions)0.36 (se = 0.06)−0.21 (se = 0.10)

Masking Indexitem 2 (alcoholic intake)−0.17 (se = 0.08)−0.54 (se = 0.09)
item 4 (fragranced products)−0.51 (se = 0.06)−0.35 (se = 0.11)
item 10 (routine use of medicine)0.62 (se = 0.05).0.72 (se = 0.06)