Cristina Pomirleanu, Alexandra Jitaru, Raluca Maxim, Codruta Belibou and Codrina Ancuta

ABSTRACT

Objectives. To identify predictors for Simplified Disease Activity Index (SDAI) remission in patients with established rheumatoid arthritis (RA) under 12 months of anti-TNF therapy combined with synthetic disease modyfing antirheumatic drugs (sDMARD).

Methods. We performed a prospective observational study in 90 RA patients with a high active disease refractory to sDMARDs, starting anti-TNFs. Patients were assessed every 3 months based on a well-defined protocol, including individual parameters (clinical, inflammatory) and composite tools (simplified disease activity index SDAI, functional index HAQ-DI); total and IgA-isotype rheumatoid factor (RF) as well as anti-citrullinated peptide antibodies (ACPAs) were measured at baseline, 6 and 12 months. Therapeutic response was evaluated according to EULAR criteria. The primary endpoint was SDAI remission (≤ 3.3) at 12 months of treatment. Univariate and multivariate logistic regression analysis (Forward LR method) were used to assess the manner and intensity in which several parameters (demographics, disease-related, labs and medication) power SDAI remission.

Results. SDAI remission was reported in 39.7% cases. We identified nine relevant predictors for SDAI remission at 12 months of therapy by univariate analysis, including: age ≤ 50 years, disease onset ≤ 5 years, RA stages I and II, functional capacity stages I and II, HAQ-DI ≤ 2, concomitent sDMARD, baseline CRP ≤ 20 mg/l, IgA-RF ≤ 20 IU/ml and ACPAs ≤ 40 IU/ml. A mathematical model was further generated, based only on six out of nine parameters: age, disease stage, functional capacity, concomitent sDMARDs, CRP and ACPA. This model expressesa solid approximation for the analysed casess (the Hosmer-Lemeshow test λ² = 0.931, p = 0.920 ≥ 0.05, Cox and Snell R2 0.399). Finally, three significant factors were recognized (age under 50, disease stages I and II, ACPA levels ≤ 40 IU/ml), predicting SDAI remission with an overall constant precision of 83.3%. However, no significant impact on SDAI remission prediction was reported when adding other parameters to the above mentioned model.

Conclusion. SDAI remission can be predicted in established RA patients using three major predictors, including age ≤ 50 years, disease stages I and II and baseline ACPA levels ≤ 40 IU/ml.

Keywords: anti-TNF agents, established rheumatoid arthritis, predictors, remission, SDAI

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Cristina Pomirleanu, Alexandra Jitaru, Raluca Maxim, Codruta Belibou and Codrina Ancuta

ABSTRACT

Objective. To identify predictors for Simplified Disease Activity Index (SDAI) remission in established rheumatoid arthritis (RA) and to develop a predictive score for remission.

Methods. Prospective 12-month observational study in ninety active RA receiving their first TNF-α inhibitor. Standard assessments consisted of disease activity scores (DAS28-ESR, SDAI) and immune parameters (total rheumatoid factor, RF; IGA-RF; anti-cyclic citrullinated peptide antibodies, ACPA). The primary outcome measure was SDAI remission (≤ 3.3) at 12 months. Univariate and multivariate logistic regression models were used to estimate association between baseline variables and SDAI remission.

Results. 39.7% RA achieved remission, while 56.8% low disease activity. Significant association between SDAI remission and RA-onset before 50 (p = 0.000), history <5 years (p = 0.000), stage (p = 0.000), class I and II Steinbroker functional status (p = 0.022), HAQ-DI≤2 (p = 0.034), CRP ≤ 20mg/l (p = 0.041), IgA-RF ≤ 20 IU/ml (p = 0.002), ACPA ≤ 40 IU/ml (p = 0.047), concomitant DMARDs (p = 0.003) were identified. Four parameters independently predicted 12-month remission (age at onset under 50, RA duration <5 years, ACPA≤40 IU/ml, IgA-RF ≤ 20 IU/ml) as demonstrated by multivariate logistic regression (p<0.05), making correct prediction in 84.4% patients. Furthermore, the remission score correctly classified 90.6% RA, while the transformed simplified version up to 89.4% cases. Gender, clinical parameters and ESR were not predictors for treatment response (p > 0.05).

Conclusion. SDAI remission can be predicted in established RA using a score based on age at onset, disease duration, titers of ACPA and RF isotype A. Such a simplified score may help clinicians to manage remission in RA patients according to the current treatment guidelines.

Keywords: anti-TNF agents, established rheumatoid arthritis, predictors, remission, SDAI

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