Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.
Consequence of Remission Misclassification Due to Reduced Joint Counts Omitting the Forefeet.
van Tuyl8, Lilian H. D., Britsemmer3, Karin, Felson2, David T., Wells6, George A., Smolen4, Josef S., Zhang1, Bin, Funovits5, Julia
Boston Univ Schl of Medicine, Boston, MA
Boston University School of Medicine, Boston, MA
Jan van Breemen Institute
Krankenhaus Lainz, Vienna, Austria
Medical University of Vienna
Univ of Ottawa Faculty of Med, Ottawa, ON, Canada
VU University Medical Center, Amsterdam, The Netherlands
VU University Medical Center, Amsterdam
Introduction:
With remission in rheumatoid arthritis (RA) a realistic outcome of treatment, the ACR, EULAR and OMERACT have joined forces to develop a new definition for remission in RA to be used in clinical trials. One of the issues on the research agenda is the consequence of using a 28- vs a more complete joint count. Several studies report residual disease activity in the feet in patients with a 28-joint count of zero, although this might not be a problem in defining remission if such patients fail to classify because of activity in other measures within the definition.
In an observational early disease cohort we studied the consequences of misclassification due to residual disease activity in the feet of patients in remission by 28-joint counts.
Methods:
All patients fulfilling the '87 ACR criteria for RA at inclusion or at 1 year follow up in the early arthritis cohort of the Jan van Breemen Institute (Amsterdam, The Netherlands), not using biologicals were included.
Boolean as well as index-based candidate remission definitions were calculated using the 28- and 38 joint count that includes the 10 metatarso-phalangeal joints. Disease stability was defined as stable x-ray scores over 1 year (change <=0 in van der Heijde/Sharp scores) AND stable and low scores on the Health Assessment Questionnaire (HAQ change <=0 AND HAQ score consistently <=0.5), all during the 2nd year after inclusion.
Analyses comprised: 1) residual disease activity (swollen or tender joints>0) in the feet of patients that fulfilled the candidate remission criteria using a 28 joint count; 2) likelihood ratio's of remission definitions to predict disease stability.
Results:
Of a total of 423 RA patients 8 to 30% reached remission at 1 year using a 28 joint count (Table 1).
Table 1. Count(%) of patients in remission with active feet
The 6-measure Boolean definition is most strict, the DAS28<2.6 most relaxed. Of these, 26 to 44% showed activity in the feet, ~70% being due to both swelling and tenderness. Misclassification due to reduced joint counts was observed in 2 to 3 % of patients measured with a Boolean definition.
A state of remission increased the likelihood of stability of both x-ray and HAQ, with slightly higher LRs for definitions using 38 joint counts vs definitions using 28 joint counts.
Table 2. Likelihood ratio's of remission definitions with 28 vs 38 joint counts to predict disease stability
Conclusion:
A substantial proportion of patients in remission according to 28 joint counts show activity in the feet. Actual misclassification occurs in 2–3% of the total population studied. The ability of remission definitions with 28 vs 38 joint counts to predict long term good radiological and functional outcome is highly similar.
To cite this abstract, please use the following information:
van Tuyl, Lilian H. D., Britsemmer, Karin, Felson, David T., Wells, George A., Smolen, Josef S., Zhang, Bin, et al; Consequence of Remission Misclassification Due to Reduced Joint Counts Omitting the Forefeet. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :723
DOI: 10.1002/art.28491
