ACPA	anti-citrullinated protein/peptide antibody
AU	arbitrary unit
Anti-CCP2	anti-cyclic citrullinated peptide version 2
BMI	body mass index
CANO	alveolar NO
CawNO	NO content in the airway walls
CV	coefficient of variation
DAS28	Disease Activity Score for 28 joints
DawNO	NO diffusion capacity over the airway wall
ESR	erythrocyte sedimentation rate
FENO,50	fraction of exhaled nitric oxide at a flow of 50 mL/s
FEV1	forced expiratory volume at 1 s
FVC	forced vital capacity
HAQ	Health Assessment Questionnaire
HMA	Högman–Meriläinen algorithm
Ig	immunoglobulin
mAb	monoclonal antibody
NO	nitric oxide
iNOS	nitric oxide synthase
NOx	nitrate/nitrite in serum
OD	optical density
PAD	peptidyl arginine deaminase
Poly Ig	polymeric immunoglobulin
ppb	parts per billion
RF	rheumatoid factor
Rgp	arginine gingipain
SC	secretory component
CRP	C-reactive protein
TNF	tumour necrosis factor