In this study of patients with early RA, the HAQ-DI-UE decreased significantly from inclusion to the 6-month follow-up. HAQ-DI-UE levels were stable between 6 month and 2 years, whereas between 2 years and 5 years, there was a significant increase. Furthermore, there were strong correlations for HAQ-DI-UE with grip force and PROMs at all time points, and moderate to weak correlations with joint counts and laboratory parameters of inflammation. The strong and consistent negative association between grip force and disability related to the UE underlines the importance of the grip in this context.
Involvement of several joint groups contributed to disability related to the upper extremities. At inclusion wrist synovitis and tender PIP joints had both an independent impact on HAQ-DI-UE, whereas tenderness of the shoulder and the wrist had a greater importance at 6 months.
Our results suggest that patients with poor PROMs in early RA are at increased risk of persistent limitations in daily life activities that are performed using the UE. Previous studies have investigated disability overall, and not the HAQ-DI-UE. Disease activity, measured as swollen and tender joint counts, as well as pain, have both been shown to be associated with the total HAQ score (32). Several other studies demonstrated similar results, with associations between high disease activity and impaired PROs like HAQ (17, 33–35).
One of these compared two large inception cohorts of patients with early RA, the Early Rheumatoid Arthritis Study (ERAS, inclusion period 1986–1997), and the Norfolk Arthritis Register (NOAR, 1990–1994), both from the United Kingdom (33). Both these studies analyzed trajectories, i.e. patterns of progression of disability (33). The overall pattern for HAQ-DI was similar to our observations on HAQ-DI-UE. They also reported an association with DAS28 (33) but did not investigate the importance of the subcomponents (swollen, tender, ESR, VAS pain and VAS Global), in contrast with our study.
In a study based on the Canadian Early Arthritis Cohort (CATCH), the HAQ-DI and DAS28 decreased significantly over time from baseline to 24 month (34), but no further follow-up was reported. The Swedish TIRA study (Early Interventions in Rheumatoid Arthritis) group reported that disability decreased significantly during the first year after inclusion in their inception cohort (1). This was followed by gradually worsening of disability up to the 8-year follow-up (1). In that study, grip force and pain intensity were major contributors to disability measured using HAQ-DI (1), similar to our findings on HAQ-DI-UE. Taken together, these studies suggest that although disability may decrease in early RA, subsequent worsening of disability is common, in particular in those with active disease and severe pain (1, 33, 34).
In a study of early RA, performed by the Swedish BARFOT (Better Anti-Rheumatic FarmacOTherapy) group, outcomes including the disease activity score, VAS pain, Patient Global Assessment (PatGA) and HAQ were followed during five years (35). Interestingly, patterns were similar in patients diagnosed 1992–1999 and 2000–2006, with no difference in VAS pain or HAQ-DI between the groups, despite the fact that the latter group was more actively treated (35). The authors suggest that other mechanisms than inflammation might be of importance for persistent disability and pain (35). This is in accordance with the results of the present study, with limited correlation between HAQ-DI-UE and markers of inflammation, in particular with long term follow-up.
A major impact of reduced grip force on disability has been demonstrated in several previous studies (1, 3, 18, 19, 32), including a survey of the cohort investigated in the present study (6). This suggests that hand training should be beneficial in early RA. Indeed, structured rehabilitation, including tailored exercise program for the distal UE have been shown to improve the grip strength and reduce the impact of the disease on the individual (36–38). Furthermore, multiprofessional interventions may prevent progressive disability in RA (1, 36, 37, 39).
Our results also showed a varying contribution of joint involvement to disability related to the UE. Like in the present cohort, a Japanese study of 3457 patients with established RA that analyzed the importance of change in joint involvement over time found that involvement of wrist and shoulder joints contributed significantly to worse HAQ scores in patients with RA, whereas for the small joints in the hand (MCP and PIP), the effect was modest (22). In our study, there was a greater importance for PIP joint involvement, which may characterize early RA. Furthermore, several studies found no (19, 40, 41), or limited (22), impact of involvement of the small joints in the hands on HAQ-DI. This, contrasts with our result that PIP joint tenderness was independently associated with HAQ-DI-UE at baseline. Impairment of small joints could influence particular subdimensions of the HAQ score (22), which might explain our finding.
A German study of RA patients describes that wrist involvement is strongly associated with disability, assessed by HAQ-DI (42). In a large cohort of 4 530 patients with established RA, the most frequently affected joint was shown to be the wrist (45.5%). Together with shoulders and elbows, wrist joints accounted for the greatest contributions to disease activity, HAQ-DI and long term functional prognosis (41). Several other studies demonstrated a major impact of wrist involvement on grip force in RA (19, 22, 43–45).
A limitation of the study is that the HAQ-DI-UE subscore of the HAQ-DI has not been studied before, and is not a validated outcome measure. A corresponding subscore for the lower extremities (LE), (HAQ-DI-LE) which has been used in previous studies (29–31), included 10 questions that cover activities that are mainly dependent on function of the LE. Due to the heterogeneity of RA and the differential impact on various joints in individual patients, there is a rational for constructing separate questionnaires, sorting the 20 sub dimensions in two groups, one for the LE and one for the UE. Further studies should evaluate the utility of this approach.
Another limitation in the present study is related to the loss of patients that for various reasons have not been assessed at all follow-up visits. This may lead to underestimation of long term disability in RA. However, changes over time were assessed using paired analyses of patients with data at two consecutive visits. Furthermore, due to the limited sample size, some factors that contribute to higher HAQ-DI-UE may not be identified in this study.
Strengths of this study include the structured longitudinal follow-up of an inception cohort from a defined catchment area. Therefore, selection bias is not a major issue in this study, and the results could be generalized to patients with RA seen in clinical practice. On the other hand, they may not apply to other ethnic or geographic settings, or patients managed using completely different strategies for pharmacologic treatment and rehabilitation. The protocol includes detailed documented joint assessments performed by the same rheumatologist at all follow-up visits, and structured assessment of PRO’s including the widely used HAQ-DI (46–49) at all visits.