What factors influence the health status of patients with rheumatoid arthritis measured by the SF-12v2 Health Survey and the Health Assessment Questionnaire?

OBJECTIVE

The Health Assessment Questionnaire Disability Index (HAQ) is a widely used outcome measure in rheumatoid arthritis (RA), whereas the SF-12v2 Health Survey (SF-12) was introduced recently. We investigated how the HAQ and SF-12 were associated with socio-demographic, lifestyle, and disease- and treatment-related factors in patients with RA.

METHODS

In RA patients from 11 Danish centers, clinical and patient-reported data, including the HAQ and SF-12, were collected. Three multiple linear regression models were estimated, with the HAQ, SF-12 physical component score (PCS), and SF-12 mental component score (MCS) as outcome and sociodemographic, lifestyle, and RA-related treatment and comorbidity characteristics as explanatory variables.

RESULTS

In total, 3156 (85%) of 3704 invited patients participated--75% women, 76% rheumatoid factor-positive, median age 61 years (range 15-93 yrs), disease duration 7 years (range 0-68 yrs), Disease Activity Score on 28 joints (DAS28) 2.97 (range 0.96-8.61), HAQ score 0.63 (range 0-3), SF-12 PCS 56 (range 6-99), and SF-12 MCS 57 (range 16-99). Variation in HAQ was associated with 12 of 15 possible variables (R(2) 0.41), in PCS and MCS with 6 of 15 variables (R(2) 0.02 and 0.05). Patients with moderate to high DAS28 and > or = 3 comorbid conditions had consistently worse HAQ and SF-12 scores compared to the reference groups, while weekly exercise was associated with better scores compared to no exercise.

CONCLUSION

The HAQ was more sensitive to differences in demographic, lifestyle, and disease- and treatment-related factors than the SF-12. The established clinical value and feasibility of the HAQ highlights its advantages over the SF-12 in describing health status in RA.