13135-item version of the questionnaire. Finally a test–retest postal survey was con-
ducted to improve the scaling properties, reliability, internal consistency, and valid-
ity. Rasch analysis of data from this postal survey identifi ed a 20-item version with
good item fi t and excellent psychometric properties (internal consistency 0.91, test–
retest reliability 0.89, and good external construct validity). The fi nal 20 items of
the questionnaire consisted, as far as possible, of wording taken from the transcripts.
They cover various domains of impact such as physical problems, fatigue, emo-
tional, and social problems (Table 5.4 ).
Sensitivity and responsiveness to change have been further assessed in 28 PsA
patients, demonstrating signifi cant change at 3 and 6 months after change of dis-
ease modifying therapy ( p < 0.01 and p < 0.05, respectively) [ 54 ]. Standardized
response mean was large at 3 months (0.71) and small at 6 months (0.41). The
PsAQoL has been translated and validated in Dutch and Swedish [ 55 , 56 ]. In sum-
mary, the PsAQoL is a disease-specifi c instrument that is derived directly from
qualitative interviews, has good psychometric properties, and is quick and easy to
Table 5.4 Domains of health important for patients with PsA as refl ected in two patient-derived
questionnaires assessing impact of PsA
Domains of health16 Domains identifi ed in
the PsAID development
process [ 52 ]20 Domains of
health included in
the PsAQoL [ 53 ]
Pain X
Skin problems X
Fatigue X X
Ability to work/leisure X
Functional capacity (capacity to perform daily
physical activities, loss of independence)X XFeeling of discomfort X
Mobility X
Morning stiffness X
Sleep disturbance X
Anxiety, fear, and uncertainty X
Anger, irritation X
Coping X X
Embarrassment and/or shame due to
appearanceXSocial participation X X
Depression X X
Relationship with family X X
Concentration diffi culties X
Rejection and discrimination due to appearance X
Sexual life XPsA psoriatic arthritis, PsAID Psoriatic Arthritis Impact of Disease, PsAQoL Psoriatic Arthritis
Quality of Life
5 PROMs for Spondyloarthritis