Background/Purpose:   Sustained clinical remission (REM) is the therapeutic goal in rheumatoid arthritis (RA) but low disease activity (LDA) may be acceptable.  Little is known whether sustained LDA is “as good” as sustained REM for reducing disability in early rheumatoid arthritis (ERA). Our objectives were to : (1) compare the prevalence of sustained REM and sustained LDA in ERA patients and describe any differences in core variables among the groups and; (2) determine if sustained REM and LDA are independently associated with function, measured by the health assessment questionnaire disability index (HAQ-DI).

Methods:  ERA patients with at least 2 years of follow-up in the Canadian early ArThritis CoHort (CATCH) (N=833) were included in the analysis. REM/LDA was classified according to the clinical disease activity index (CDAI; ≤2.8 vs. 2.9-10) and simplified disease activity index (SDAI; ≤3.3 vs. 3.4-11). REM and LDA was defined as sustained if present for ≥ 2 consecutive visits or ≥ 6 months during the first 18 months. Linear regression models were performed with HAQ-DI score at 2 years as the outcome, and each REM or LDA definition as the independent variable, adjusted for baseline confounders.

Results: Only 77 (9%) patients achieved sustained REM by each the CDAI and SDAI definitions over the first 18 months. 426 (51%) were in sustained CDAI LDA and 333 (40%) were in sustained SDAI LDA. At baseline, there were no significant differences in demographic, clinical, laboratory or early treatment variables between patients in REM vs. LDA by either index.  At follow-up, mean HAQ-DI scores for those in sustained REM ranged from 0.10 to 0.13 compared to baseline HAQ-DI (range 0.87-1.0) and scores were 0.39-0.40 at follow-up for those in sustained LDA compared to their baseline values ranging from 0.97-0.98.  Overall, HAQ-DI scores were significantly lower at year 2 for those achieving sustained REM compared to sustained LDA (table). Joint counts, pain, fatigue and global health assessment were also significantly lower in the REM groups (table). Multivariable regression analyses showed that sustained CDAI REM and sustained SDAI REM were both independently associated with lower HAQ-DI than sustained LDA (p<0.001).

Conclusion:  HAQ-DI scores at year 2 are significantly lower among patients who achieve sustained REM vs. sustained LDA.  This difference is greater than the minimal clinically important difference for HAQ of 0.22, suggesting there are clinically important differences in long term function based on best achieved sustained disease activity state. Further study is needed to understand what influences achieving sustained REM as opposed to sustained LDA in early RA.

Table. HAQ-DI scores and differences in core variables among patients achieving sustained REM vs. LDA according to CDAI and SDAI cut-offs at year 2.

	CDAI			SDAI
	Sustained REM	Sustained LDA	p	Sustained REM	Sustained LDA	p
TJC-28, mean ± SD	0.46 ± 1.21	1.34 ± 2.81	0.002	0.58 ± 1.84	1.42 ± 2.88	0.001
SJC-28, mean ± SD	0.58 ± 1.70	0.88 ± 2.00	0.009	0.42 ± 1.27	0.92 ± 1.97	0.002
CRP, mean ± SD mg/L	5.29 ± 8.71	5.37 ± 8.55	0.87	5.37 ± 9.08	5.34 ± 8.79	0.58
ESR, mean ± SD mm/hr	14.3 ± 12.0	15.1 ± 14.8	0.988	12.9 ± 11.7	14.9 ± 14.5	0.27
Pt-GA, mean ± SD cm (0-10 cm)	0.68 ± 1.33	2.42 ± 2.53	<0.001	0.89 ± 1.57	2.30 ± 2.45	<0.001
MD-GA, mean ± SD cm (0-10 cm)	0.36 ± 0.93	0.78 ± 1.30	<0.001	0.43 ± 1.08	0.77 ± 1.29	0.01
VAS pain, mean ± SD cm (0-10 cm)	8.60 ± 15.9	23.4 ± 24.5	<0.001	10.7 ± 18.3	22.0 ± 23.0	<0.001
VAS fatigue, mean ± SD cm (0-10 cm)	12.9 ± 21.4	26.4 ± 26.6	<0.001	15.3 ± 22.7	24.9 ± 25.1	<0.001
HAQ-DI, mean ± SD	0.10 ± 0.20	0.40 ± 0.55	<0.001	0.13 ± 0.26	0.39 ± 0.53	<0.001

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/do-sustained-clinical-remission-and-sustained-low-disease-activity-equally-predict-functional-status-in-early-rheumatoid-arthritis/