Artikel
Achievement of individual meaningful response measured by DAS28dcrit in active Rheumatoid Arthritis when treated with Tocilizumab: Data from a large prospective observational study
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Veröffentlicht: | 29. August 2016 |
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Background: Normal fluctuations in results of disease-activity-measurements due to short-term situational effects and measurement errors are issues for evaluation of individual clinically meaningful therapeutic response in daily practice in RA-patients. We established a statistical approach to determine a critical difference (dcrit) that defines valid criterion for response as assessed by the Disease-Activity-Score-28 joints (DAS28) . With this study the DCRIT-criterion was used to measure clinical meaningful response in RA-patients treated with Tocilizumab (TCZ) in routine care.
Methods: The patient population was derived from a prospective non-interventional study in RA-patients TCZ-treated. A total of 635 patients was analyzed. 310 patients with stable disease and on stable therapy for at least one year were used to evaluate DAS28dcrit cut-off of 1.8 for response. To evaluate individual variations in DAS28-scores, we subjected patients’ DAS28-scores at 12, 18, 24 months to an ANOVA model to establish a 95% one-sided confidence-interval for normal fluctuations. The total cohort was used to calculate percentage of patients achieving DAS28dcrit-response.
Results: The mean baseline DAS28 from the stable cohort was 5.52 and decreased to month 12 to 2.51. For the next year of treatment, the mean DAS28 of the entire cohort was stable without differences (month 15 2.44, month 18 2.40, month 21 2.44, month 24 2.46). The calculation of the dcrit cut-off in TCZ-monotherapy results in 1.81 (n=80); for the population including combinational-therapy 1.9 (n=72). 70.5% patients of the total cohort achieved DAS28dcrit after 12 weeks. The responders increased up to 76.0% at week 24., 78.9% at week 52 (dcrit cut-off 1.8). After 2-years of treatment 80.6% of the patients reached a stable DAS28dcrit-response over time. If using the cut-off of 1.9 the result reads as follows: 64.5% at week 12, 73.8% at week 24, 77.3% at week 52, 77.6% at week 104.
Conclusion: The established DAS28dcrit of 1.8 was confirmed in an independent cohort of TCZ-treated patients. Its slightly higher value in TCZ treated patients (especially in TCZ+DMARD) might be due to the unique effect of TCZ on one variable of DAS28 (ESR/CRP). For both cut-offs (1.8 and 1.9) high percentages of patients achieved this level of response after TCZ-initiation.