Defining minimal disease activity in psoriatic arthritis: a proposed objective target for treatment.
OBJECTIVE
To create minimal disease activity (MDA) criteria for psoriatic arthritis (PsA). With recent therapeutic advances, this is now a goal for treatment and may represent a measure to compare therapies. It defines a satisfactory state of disease activity rather than a change, and encompasses all aspects of the disease.


METHODS
40 patient profiles were sampled from an observational PsA database. Sixty experts in PsA classified these as in MDA or not. A consensus of > or =70% was accepted, identifying 13 profiles in MDA. Summary statistics created possible cut-off points for the definition. Considering the number of measures that must be met, 35 candidate definitions were created and tested using receiver operating characteristic curves (ROC) for sensitivity and specificity.


RESULTS
Four candidate definitions showed high area under the curve values on ROC testing. Definitions with high outlying values were excluded as they were not considered to represent MDA. Aiming for high specificity to reduce false positives resulted in a preference for the following definition: "A patient is classified as achieving MDA when meeting 5 of the 7 following criteria: tender joint count < or =1; swollen joint count < or =1; Psoriasis Activity and Severity Index < or =1 or body surface area < or =3; patient pain visual analogue score (VAS) < or =15; patient global disease activity VAS < or =20; health assessment questionnaire < or =0.5; tender entheseal points < or =1".


CONCLUSIONS
This study provides the first definition of a "state" of MDA in PsA and defines a target for treatment. It must now be validated in other populations and tested in clinical trials.
Coates
L C
LC
Academic Unit of Musculoskeletal Disease, University of Leeds and Chapel Allerton Hospital, Leeds LS7 4SA, UK.
Fransen
J
J
Helliwell
P S
PS
D018501:Antirheumatic Agents / Q000627:therapeutic use*; D015535:Arthritis, Psoriatic / Q000175:diagnosis / Q000188:drug therapy*; D005104:Expert Testimony; D006801:Humans; D015588:Observer Variation; D010147:Pain Measurement; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016896:Treatment Outcome
D018501:Antirheumatic Agents