Background/Purpose

Co-morbidity has been shown to increase length of hospital stay and mortality in hospitalised patients. However, in early rheumatoid arthritis (eRA) co-morbidity may confound treatment response and affect disease severity measures (disease activity scores (DAS28) and health assessment questionnaire (HAQ)).

The study aims were to assess:

1) Whether self reported comorbidity correlates with baseline DAS28 & HAQ in an eRA cohort? 

2) Does co-morbidity burden predict DAS28 remission and HAQ after 1yr of treatment?

Methods:

At time of eRA diagnosis, patients completed a modified validated self-reported 14 item comorbidity questionnaire (1). Each co-morbidity item scores 1 point (maximum score 14). Use of treatment or associated impairment contributes to a weighted co-morbidity score (Maximum score 36). The number of comorbidity items were divided into 3 categories: low≤1, medium=2 , & and high ≥3. Correlation between co-morbidity number and weighted score and DAS28 and modified mHAQ were assessed at baseline using Spearman’s rank correlation.

Logistic regression (adjusting for age, gender, smoking, obesity, & seropositive status) were used to explore whether baseline co-morbidity:1) number & 2) weighted score, predicted 1yr DAS28 remission & high HAQ (defined as >1).

Results

147 eRA patients, with symptom duration less than 12 months, mean age 58.1yrs & 67% female, had complete baseline and 1yr data. All were treated with synthetic DMARDS following a treat to target regime.

At baseline, comorbid disease was reported by 107 (72.8%) with median number of 1 [ IQR 0, 3] comorbid conditions in addition to RA.  The median weighted co-morbidity score was 2 [ IQR 0, 3]. Patients reporting ≥2 co-morbidities had higher prevalence of high HAQ>1 and DAS28> 5.1. Modest correlation was observed between the number of co-morbidities and 1)DAS28- rho 0.23, (p<0.05) and 2)HAQ- rho 0.31(p<0.01).

After 1 year, 77 (52.4%) achieved DAS28 <2.6 and 28 (19.1%) had HAQ score >1. Reporting 2 or more co-morbidities was associated with reduced rates of DAS28 remission and high HAQ score at 1 year (table 1). Increasing numbers of co-morbidity and use of the co-morbidity weighted scores did not increase the strength of association.

 

Table1:- Predictors of disease severity after 1 year			DAS28<2.6	1 year HAQ >1
Comorbidity		n	ORadj (95%CI)	ORadj  (95%CI)
Number	0-1 (ref)	90	1.0	1.0
	2	23	0.35 (0.13, 0.94)	2.16 (0.63, 7.31)
	>=3	34	0.46 (0.19, 1.56)	5.16 (1.64, 16.24)
Weighted	0-1 (ref)	58	1.0	1.0
	2-3	44	1.31  (0.57, 3.03)	2.48 (0.79, 7.77)
	>=4	45	0.30 (0.12, 0.74)	4.11 (1.26, 13.3)

Conclusion

Self reported comorbid disease burden predicts disease activity and level of disability in an eRA cohort after 1 year of treatment. Weighting co-morbidity for severity and function do not increase the strength of association with 1 year outcomes in early RA. Adjusting for the confounding effects of co-morbidity is important when assessing response to treatment. Use of self reported co-morbidity questionnaires appear to be an acceptable method of quantifying co-morbidity in routine rheumatology outpatient departments.

1)      Sangha O, et al. The Self-Administered comorbidity questionnaire:A New Method to Assess Comorbidity for Clinical and Health Services Research.  Arthritis Rheum 2003;49:156-63.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/co-morbidity-is-associated-with-disease-severity-in-early-rheumatoid-arthritis/