RAPID3 Shown to Be an Effective Assessment Tool for Patients with Psoriatic Arthritis

New research suggests that a 10-second self assessment might provide nearly as much information about psoriatic arthritis case progression as complex tests that generally require either require laboratory results or formal joint-by-joint evaluation.

Data from 2 trials, dubbed PRESTA and PREPARE, were analyzed to see how much patient scores on the very speedy RAPID3 self-assessment compared with their scores on 4 validated measures of psoriatic arthritis severity: DAS28-CRP, CDAI, CPDAI, and DAPSA. The researchers made comparisons using intraclass correlation coefficients (ICCs). Treatment effect sizes were calculated for change from baseline to week 24 for the PRESTA and agreement in disease activity classifications were compared at baseline for both trials.

There was a moderate degree of overall correlation between RAPID3 and the other indices, but individual comparison results varied considerably. At baseline in the PREPARE trial, RAPID3 was most closely correlated to DAS28 (ICC, 0.64; 95% confidence interval [CI], 0.60-0,67) and CDAI (ICC, 0.64; 95% CI, 0.61-0.68) and least correlated with DAPSA (ICC, 0.58; 95% CI, 0.54-0.62). At baseline in the PRESTA trial, the correlations were much lower. RAPID3 was most closely correlated to DAS28 (ICC 0.56; 95% CI, 0.51-0.62) and least correlated with CDAI (ICC, 0.40; 95% CI, 0.33-0.47).

By the end of the PRESTA trial, however, correlations had increased substantially. RAPID3 was, once again, most correlated with DAS28 (ICC, 0.67; 95% CI, 0.63-0.72) and least correlated with DAPSA (ICC, 0.57; 95% CI, 0.52-0.63).

Such correlations may seem far too low to make RAPID3 a reliable tool for measuring the severity of psoriatic arthritis, but they are, in many cases, nearly as great as the correlations among the more arduous diagnostic formulas that have already been validated. For example, the study found that CPDAI was only slightly better correlated at baseline in the PREPARE trial with DAS28 (ICC, 0.66; 95% CI, 0.64-0.71) than was RAPID3 (ICC, 0.62; 95% CI, 0.58-0.66).

In general, correlations between DAS28 and either CDAI or DAPSA were better than correlations between RAPID3 and any of the other measures, but correlations between CPDAI and the other indices were little better than their correlations with the quicker assessment.

“In clinical trials of psoriatic arthritis, the performance of RAPID3 proved to be satisfactory relative to other composite indices,” the study team wrote on a poster presented at the annual Congress of the European League Against Rheumatism.“Although additional research is needed, RAPID3 may provide a practical tool for use in the routine clinical care of this condition.”

The Routine Assessment of Patient Index Data 3 has already been validated as an assessment of rheumatoid arthritis and several other rheumatoid conditions. It asks patients how easily they can perform 13 tasks (i.e. getting in and out of bed) and then asks them to assess their overall pain and wellbeing on a scale of 0 to 10.

The RAPID3 takes less time, by at least a full order of magnitude, than any of the other tests on the list. The DAS28, by contrast, requires a full count both tender and swollen joints as well as a laboratory analysis of fluid samples. The relative complexity of these other tests often prevents clinicians from making formal assessments of psoriatic arthritis progression when they should and, therefore, can make it hard to evaluate the treatment needs of patients and evaluate the efficacy of treatments.