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Published on: November 4, 2017
Concordance and agreement between different activity scores in polymyalgia rheumatica
Justine D'Agostino1, Aghiles Souki2, Anne Lohse3
1Department of Rheumatology, Centre Hospitalier Universitaire de Brest, Brest, France justine.dagostino@chu-brest.fr.
Objective:
The C reactive protein polymyalgia rheumatica activity score (CRP-PMR-AS) is a composite index that includes CRP levels and was developed specifically for PMR. As treatments such as interleukin-6 antagonists can normalise CRP levels, the erythrocyte sedimentation rate (ESR) of PMR-AS, the clinical (clin)-PMR-AS and the imputed-CRP (imp-CRP)-PMR-AS have been developed to avoid such bias. Our primary objective was to measure the correlation of these activity scores. Our secondary objective was to evaluate the concordance between different cutoffs of the PMR-ASs.
Method:
Data from the Safety and Efficacy of tocilizumab versus Placebo in Polymyalgia rHeumatica With glucocORticoid dEpendence (SEMAPHORE) trial, a superiority randomised double-blind placebo-controlled trial, were subjected to post hoc analysis to compare the efficacy of tocilizumab versus placebo in patients with active PMR. The CRP-PMR-AS, ESR-PMR-AS, clin-PMR-AS and imp-CRP-PMR-AS were measured at every visit. The concordance and correlation between these scores were evaluated using kappa correlation coefficients, Bland-Altman correlations, intraclass correlation coefficients (ICCs) and scatter plots.
Results:
A total of 101 patients were included in the SEMAPHORE trial, and 100 were analysed in this study. The correlation between the PMR-ASs was excellent, as the ICC and kappa were >0.85 from week 4 until week 24 (CRP-PMR-AS ≤10 or >10). Bland-Altman plots revealed that the differences between the CRP-PMR-AS and the other threescores were low. The cut-off values for the clin-PMR-AS were similar to those for the CRP-PMR-AS 86% of the time.
Conclusion:
The correlation between all the PMR-ASs was excellent, reflecting the low weight of CRP. In clinical trials using drugs that have an impact on CRP, the derived activity scores can be used.
Trial Registration Number:
NTC02908217.
Insights
The C-reactive protein polymyalgia rheumatica activity score (CRP-PMR-AS) and its variants show excellent correlation in PMR patients. These scores are reliable for clinical trials, even with treatments affecting CRP levels.
Area of Science:
- Rheumatology
- Clinical Trial Methodology
- Biomarker Analysis
Background:
- Polymyalgia rheumatica (PMR) activity is often assessed using the C-reactive protein polymyalgia rheumatica activity score (CRP-PMR-AS).
- Treatments like interleukin-6 antagonists can normalize CRP levels, potentially biasing CRP-PMR-AS in clinical trials.
- Alternative scores, including erythrocyte sedimentation rate (ESR)-PMR-AS, clinical (clin)-PMR-AS, and imputed-CRP (imp-CRP)-PMR-AS, have been developed to mitigate this bias.
Purpose of the Study:
- To measure the correlation between different polymyalgia rheumatica activity scores (PMR-ASs).
- To evaluate the concordance between various cutoffs of the PMR-ASs.
- To assess the utility of derived PMR activity scores in clinical trials involving drugs that impact CRP levels.
Main Methods:
- Post hoc analysis of data from the Safety and Efficacy of tocilizumab versus Placebo in Polymyalgia rHeumatica With glucocORticoid dEpendence (SEMAPHORE) trial.
- Measurement of CRP-PMR-AS, ESR-PMR-AS, clin-PMR-AS, and imp-CRP-PMR-AS at all study visits.
- Evaluation of correlation and concordance using kappa correlation coefficients, Bland-Altman correlations, and intraclass correlation coefficients (ICCs).
Main Results:
- Excellent correlation was observed between all PMR-ASs, with ICC and kappa values consistently above 0.85 from week 4 to week 24.
- Bland-Altman plots indicated low differences between the CRP-PMR-AS and the other three scores.
- The cut-off values for the clin-PMR-AS aligned with those for the CRP-PMR-AS in 86% of cases.
Conclusions:
- All evaluated PMR-ASs demonstrate excellent correlation, suggesting their reliability in assessing disease activity.
- The low weight of CRP in the overall correlation indicates the robustness of these scores.
- Derived activity scores are suitable for use in clinical trials, particularly those employing drugs that influence CRP levels.
