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the following questions: “Considering all the ways your joints have affected you
during the last week, circle the number that best describes how you have been
doing” and “Considering all the ways psoriasis (skin disease) has affected you dur-
ing the last week, circle the number that best describes how you have been doing”
[ 52 , 67 , 68 ].
In an initial study, PGA appeared to be related to both of these patient assess-
ments [ 68 ].
We recently showed in 223 PsA patients that intra-class correlation between
PGA and joint or skin patient assessment were, respectively, 0.71 (95 % confi dence
interval, 0.64–0.77) and 0.52 (95 % confi dence interval, 0.42–0.60) [ 72 ]. This indi-
cates the joint global assessment proposed by GRAPPA may be redundant with
PGA, whereas the skin global assessment may bring additional and different infor-
mation. Furthermore, in multivariate analysis PGA was explained ( R 2 of model
0.75) by coping ( β [beta] = 0.287), pain ( β [beta] = 0.240), work and/or leisure activi-
ties ( β [beta] = 0.141), and anxiety ( β [beta] = 0.109) [ 72 ]. Thus PGA in PsA is
explained by physical aspects of impact, such as pain and activities, but also psy-
chological aspects: coping and anxiety. In this study, skin impact was not an addi-
tional explanatory factor of PGA, perhaps because many of the patients had limited
skin involvement [ 49 ].
Pain
Pain is a widely assessed outcome in PsA, often using a single question VAS or NRS
though the wording may vary slightly. One validated formulation of the pain question
is the following: “Circle the number that best describes the pain you felt due to your
psoriatic arthritis during the last week” with anchors going from “none” to “extreme.”
Pain is a major component of the impact of PsA and is reported by patients as the
most important domain of health in this disease, as is also the case in RA [ 52 , 73 , 74 ].
The interpretation of improvement in pain in PsA rests on the Minimal Clinically
Important Difference cutoff, which has been validated as an improvement from
baseline of at least 10 points on a 0-100 scale [ 75 ].
Fatigue
Fatigue is a subjective experience that can be described as an overwhelming, sus-
tained sense of exhaustion and decreased capacity for physical and mental work.
Levels of fatigue in PsA are elevated: in a large cross-sectional cohort almost 50 %
of PsA patients reported moderate fatigue and 29 % experienced severe fatigue [ 76 ].
The importance attributed to fatigue is also high: In a priority exercise of 474
patients with PsA from 13 countries, patients ranked fatigue as the second most
important domain after pain and before skin problems [ 52 ].
There is no consensus regarding which instrument should be used to assess
fatigue in PsA. In a systematic literature review on clinical outcomes in PsA, the
U. Kiltz et al.