Background/Purpose

In RA the target for treatment is clinical remission or minimal disease activity. Patient involvement in monitoring their disease activity could enhance treatment by providing early warning when targets are not met, indicating the need to re-evaluate treatment. Several patient reported outcome measures of disease activity have been developed and validated. The objective of this study is to compare the agreement between patient and rheumatologist (MD) derived disease activity states using these measures.

Methods

Consecutive RA patients seen by 7 rheumatologists were invited to participate. Patients completed a questionnaire before their visit. MD joint count and lab values were obtained from charts. We evaluated 4 patient reported disease activity measures: i) PASII; ii) RAPID with 3 measures (RAPID3); iii) RAPID with 4 measures (RAPID4); iv) modified-RAPID4 (m-RAPID4) using HAQII instead of MDHAQ. The following MD derived measures served as gold standards: i) Clinical Disease Activity Index (CDAI); ii) Simplified Disease Activity Index (SDAI); iii) Disease Activity Score 28 (DAS28). Disease states were categorized into remission, low, moderate or high, according to published cut points. Because change in treatment is recommended with moderate or high disease activity, we also compared two categories: remission or low vs. moderate or high. Agreement between patient and MD derived disease states was evaluated using Agreement Coefficient 1 (AC1) for two category comparisons and Agreement Coefficient 2 (AC2), weighted with quadratic weights, for four category comparisons. AC values > 0.62 were considered good agreement. Z tests were used to evaluate the significance of the difference between pairs of ACs.

Results

We recruited 150 RA patients [mean (SD) RA duration: 11.9 (11.3) y; age: 57.8 (16.3) y; 81% female]. See Table 1 for agreement between patient and MD derived disease activity states. Overall, PASII showed the best agreement with MD measures. When comparing ACs for four category disease activity states, all pairwise comparisons were significantly different (all but one p < 0.001), except when comparing agreement between RAPID4 and m-RAPID4 with CDAI (p = 0.054), and between RAPID3 and RAPID4 with SDAI (p = 0.075). When comparing ACs for  two categories, significant differences were detected in the agreement between PASII and RAPID3 with CDAI, RAPID3 and 4 with CDAI, PASII and RAPID3 with DAS28, PASII and RAPID5 with DAS28 , RAPID3 and 4 with DAS28, and RAPID4 and m-RAPID4 with DAS28) (all p < 0.05).

Table 1. Agreement between patient and MD derived indices measured across four and two disease activity categories.

A	Comparison across four categories (remission vs. low vs. moderate vs. high)
PATIENT MEASURES	RHEUMATOLOGIST MEASURES
	CDAI-MD	SDAI-MD	DAS28-MD
	AC2 [95% CI]	AC2 [95% CI]	AC2 [95% CI]
PASII	0.67 [0.55, 0.79]	0.67 [0.54, 0.79]	0.47 [0.33, 0.62]
RAPID3	0.54 [0.40, 0.68]	0.60 [0.46, 0.73]	0.29 [0.14, 0.45]
RAPID4	0.60 [0.47. 0.73]	0.65 [0.52, 0.78]	0.39 [0.24, 0.54]
m-RAPID4	0.58 [0.45, 0.91]	0.64 [0.51, 0.77]	0.33 [0.18, 0.49]
B	Comparison across two categories (remission or low vs. moderate or high)
PATIENT MEASURES	RHEUMATOLOGIST MEASURES
	CDAI-MD	SDAI-MD	DAS28-MD
	AC1 [95% CI]	AC1 [95% CI]	AC1 [95% CI]
PASII	0.86 [0.83, 0.90]	0.86 [0.82, 0.90]	0.67 [0.59, 0.75]
RAPID3	0.70 [0.63, 0.76]	0.73 [0.67, 0.79]	0.29 [0.13, 0.44]
RAPID4	0.77 [0.71, 0.83]	0.78 [0.72, 0.84]	0.43 [0.29, 0.56]
m-RAPID4	0.73 [0.66, 0.79]	0.75 [0.68, 0.81]	0.35 [0.20, 0.49]
AC1 = agreement coefficient 1; AC2 = quadratic weighted agreement coefficient 2 All p-values 2 tailed, p < 0.001 Bolded values (AC > 0.62) are considered good agreement

 Conclusion

Our results suggest that patients can self-monitor disease activity. PASII shows the best agreement with all MD measures. Given the similarities in the components of the measures compared, this difference may be due to cut points used to categorize disease states.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/using-patient-reported-outcome-measures-to-classify-disease-activity-states-in-rheumatoid-arthritis-a-comparison-of-patient-activity-score-pas-and-routine-assessment-of-patient-index-data-rapid/