RESEARCH - Residual minimal disease activity in RA: a simple definition through an in-depth statistical analysis of the major outcome

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Rheumatology Advance Access published online on July 27, 2009

Rheumatology, doi:10.1093/rheumatology/kep217

Residual minimal disease activity in rheumatoid arthritis: a simple

definition through an in-depth statistical analysis of the major

outcome

Donatello Pietrapertosa1, Fausto Salaffi2, Giusy Peluso1, Silvia L.

Bosello1, L. Fedele1, Ilaria Cuoghi1, Alessandro Michelutti1,

Gremese1 and Gianfranco F. Ferraccioli1

1Division of Rheumatology, Catholic University of the Sacred Heart,

Rome and 2Rheumatology Clinic, Polytechnic University of Marche,

Ancona, Italy.

Abstract

Objective. To obtain the simplest definition of minimal disease

activity (MDA) and to compare it with published proposed definitions

of MDA in patients with RA.

Methods. Two hundred and fourteen patients with long-standing RA

(LSRA) were evaluated for clinical and laboratory parameters. Factor

analysis was performed to remove redundant variables included in the

core set measure for MDA definition stated by the OMERACT. Receiver

operating characteristic (ROC) curves analysis allowed to obtain

optimal cut-off predictors of a 28-joint disease activity score

(DAS28) 2.85. These were tested in 112 LSRA and 95 early-onset RA

(ERA) patients.

Results. Factor and ROC curve analysis showed that the best predictors

of a DAS28 2.85 in LSRA cohort were: (i) ESR <20 mm/h (sensitivity:

80%, specificity: 54%); (ii) swollen joint count (out of 28) 2

(sensitivity: 95%, specificity: 74%); (iii) patient global assessment

(0–100) 15 (sensitivity: 78%, specificity: 78%); and (iv) HAQ (0–3)

0.5 (sensitivity: 91%, specificity: 61%). To each of these four

criteria we assigned a value of 1 when it was satisfied (score

ranging: 0–4). The cut-off with the highest overall accuracy for

identifying RA patients with DAS28 2.85 was a score 3. We adopted

these four parameters in order to define the residual MDA (RMDA).

Comparing RMDA criteria, in distinct 112 LSRA and 95 ERA patients,

with OMERACT, Simplified Disease Activity Index and Clinical Disease

Activity Index definitions of MDA, we found a good agreement in the

LSRA cohort and moderate agreement in the ERA cohort.

Conclusions. HAQ, PaGA, SJC28 and ESR allow identification of RA

patients with an RMDA. The RMDA criteria behaves similarly to OMERACT

definitions, but appears more simple and feasible.

http://rheumatology.oxfordjournals.org/cgi/content/abstract/kep217v1?papetoc

Not an MD