Background/Purpose:  
Rheumatoid Arthritis (RA) is a chronic inflammatory arthritis associated
with substantial morbidity and mortality. 
Measuring disease activity in RA is important as it facilitates a
treat-to-target approach.  The purpose of
this study was to determine whether the modified version of the Disabilities of
Arm, Shoulder, and Hand (DASH), the QuickDASH, was valid in measuring disease
activity in RA.  Validity was assessed by
correlation with the Routine Assessment of Patient Index Data 3 (RAPID3).

Methods:   This prospective cohort study
gathered commenced July 2014 at a single academic facility Rheumatology
Clinic.  Subjects with a diagnosis of RA
based on 1987 or 2010 American College of Rheumatology (ACR) Classification
Criteria, depending on year diagnosed, were enrolled.  When seronegative, subjects with polyarticular symptoms and synovitis or erosions on MRI
established diagnosis.  Primary endpoint
was establishing validity of QuickDASH in routine clinical assessment of RA
disease activity through correlation with RAPID3. 

Results:   From a cohort of 98 subjects, 89
had at least 2 data points available for analysis and 178 data points were used
in paired analysis. The average patient age was 62.3 ± 13.7 years old.  Slightly more than 70% of study participants
were women and alomst 75% were Caucasian.  Seropositivity was
72.4% and 74.5% had erosive disease. 

Test-retest
reliability of the QuickDASH was excellent with an intraclass
correlation coefficient (ICC) of 0.915 (95% Confidence Interval (CI): 0.871,
0.945).  Assessed by the Pearson
correlation coefficient, the strength of the relationship between the QuickDASH
and RAPID3 questionnaire was high (r = 0.834, p < 0.0001).  The interclass reliability of the QuickDASH
to correlate with the RAPID3 was moderate with an ICC of 0.627 (95% CI:  0.498, 0.722). 

Linear regression
analysis yielded the equation QuickDASH score = (2.801* RAPID3 score) +
3.542.  Using the established disease
activity ranges for the RAPID3 questionnaire, we developed similar ranges for
the QuickDASH, as noted in the Table:

For the 4
categorical measurements of QuickDASH and RAPID3 as defined in the Table,
reliability of testing yielded an average Inter-Item Correlation of 0.786 (p
< 0.001).  Cronbach’s α was 0.879
(95% CI: 0.838, 0.910, p < 0.001). 
The measurement of agreement assessed by Kappa testing showed moderate
agreement with a Kappa of 0.481 (p < 0.001) for the QuickDASH ranges
established.

Conclusion:   This study demonstrated that the
QuickDASH was very reliable and internally consistent in the measurement of RA
disease activity.  The QuickDASH
moderately correlates with established ranges of RA disease activity
established by the RAPID3 and could potentially be used as a surrogate for the
RAPID3 in clinical practice.