DAPSA Scores Are Useful Measures of Joint Impairment and Disease Progression in Patients with Psoriatic Arthritis

Analysis of data from 2 large trials finds that cutoffs used to separate different “disease activity states” on the Disease Activity index for Psoriatic Arthritis (DAPSA) are valid. Different disease activity states are associated with different degrees of functional impairment and joint damage progression.

Investigators gathered patient information from 2 pivotal trials of tumor necrosis factor inhibitors (TNFs): IMPACT II (which tested infliximab) and Go-REVEAL (which tested golimumab). They then used the recently developed definitions of disease activity states to separate patients in remission (DAPSA ≤ 4) from patients with low (4 ≤ DAPSA ≤ 14), moderate (14 ≤ DAPSA ≤ 28) and high (DAPSA ≥ 28) disease activity. Finally, they compared how each of these groups fared on a 1-year measure of structural progression (a Sharp/van der Heijde Score modified for psoriatic arthritis) and 2 measures of functional performance (the Health Assessment Questionnaire Disability Index [HAQ] and the physical component scale of the Short Form-36 [PCS]).

The analysis used 310 GO-REVEAL patients with a mean baseline DAPSA of 48.8 (± a standard deviation of 26.4) and 130 IMPACT II patients with a mean baseline DASPA of 44.6 (±17.9). The mean HAQ for patients in each DAPSA activity state was higher than the mean HAQ for patients in the next lowest activity state (P<0.001). Mean PCS scores, on the other hand, consistently fell from each DAPSA group to the next (P<0.001).

“This association was also significant in the individual trial cohorts, and in the subgroups of patients treated with TNF inhibitors or placebo. Higher DAPSA scores were [likewise] significantly and independently associated with probability of structural progression in multiple analyses,” the study authors wrote in the Annals of the Rheumatic Diseases. “Disease activity states of the psoriatic arthritis-specific DAPSA score are highly valid for future use as endpoints in clinical trials or as targets in clinical practice.”

Full DAPSA scores are the sum of 5 variables: tender and swollen joints, patient global assessment, patient pain assessment, and C-reactive protein. The DAPSA scores and disease states evaluated by the new study can omit the measure of C-reactive protein, though, in order to make it possible to calculate scores without lab work. DAPSA also omits all consideration of skin and nail involvement.

The disease activity states that were validated by the new study were first defined in a paper published last year, also in the Annals of the Rheumatic Diseases.

Researchers asked 44 eminent rheumatologists to look at raw DAPSA data from 30 psoriatic arthritis patients. After considering each patient’s tender and swollen joint counts, each patient’s global and pain assessment and each patient’s C-reactive protein levels, the experts assigned each patient to 1 of 4 disease activity categories: remission, low, moderate or high.

Researchers then went back, calculated each patient’s DAPSA score, and found that mean DAPSA scores varied significantly for patients in each of the 4 disease activity groups. They then used the distributions of patient DAPSA scores in each group to calculate the cutoffs points that were validated in the later study.