OP0199 POINTS TO CONSIDER WHEN ANALYSING AND REPORTING COMPARATIVE EFFECTIVENESS RESEARCH WITH OBSERVATIONAL DATA IN RHEUMATOLOGY

Oral glucocorticoid use in patients with rheumatoid arthritis initiating TNF-inhibitors, tocilizumab or abatacept: Results from the international TOCERRA and PANABA observational collaborative studies

OBJECTIVE

To evaluate and compare the use of oral glucocorticoids with three classes of bDMARDs in patients with rheumatoid arthritis (RA).

METHODS

We included patients from 13 observational registries treated with a TNF-inhibitor, abatacept or tocilizumab and with available information on the use of oral glucocorticoids. The main outcome was oral glucocorticoid withdrawal. A McNemar test was used to analyse the change in the use of glucocorticoids after 1 year. Kaplan-Meier estimates and Cox regressions, adjusted for patient, treatment, and disease characteristics, were used to evaluate glucocorticoid discontinuation in patients with glucocorticoids at baseline. Because of heterogeneity, analyses were done by registers and pooled using random-effects meta-analysis.

RESULTS

A total of 12,334 participants treated with TNF-inhibitors, 2100 with tocilizumab and 3229 with abatacept were included. At one-year, oral glucocorticoid use decreased in all treatment groups (odds ratio for stopping vs. starting of 2.19 [95% CI 1.58; 3.04] for TNF-inhibitors, 2.46 [1.39; 4.35] for tocilizumab; 1.73 [1.25; 2.21] for abatacept). Median time to glucocorticoid withdrawal was ≈2 years or more in most countries, with a gradual decrease over time. Compared to TNF-inhibitors, crude hazard ratios of glucocorticoid discontinuation were 0.65[0.48-0.87] for abatacept, and 1.04 [0.76-1.43] for tocilizumab, and adjusted hazard ratios were 1.1 [0.83-1.47] for abatacept, and 1.30 [0.96-1.78] for tocilizumab.

CONCLUSION

After initiation of a bDMARD, glucocorticoid use decreased similarly in all treatment groups. However, glucocorticoid withdrawal was much slower than advocated by current international guidelines. More effort should be devoted to glucocorticoid tapering when low disease activity is achieved.

Accounting for missing data caused by drug cessation in observational comparative effectiveness research: a simulation study

Objectives

To assess the performance of statistical methods used to compare the effectiveness between drugs in an observational setting in the presence of attrition.

Methods

In this simulation study, we compared the estimations of low disease activity (LDA) at 1 year produced by complete case analysis (CC), last observation carried forward (LOCF), LUNDEX, non-responder imputation (NRI), inverse probability weighting (IPW) and multiple imputations of the outcome. All methods were adjusted for confounders. The reasons to stop the treatments were included in the multiple imputation method (confounder-adjusted response rate with attrition correction, CARRAC) and were either included (IPW2) or not (IPW1) in the IPW method. A realistic simulation data set was generated from a real-world data collection. The amount of missing data caused by attrition and its dependence on the ‘true’ value of the data missing were varied to assess the robustness of each method to these changes.

Results

LUNDEX and NRI strongly underestimated the absolute LDA difference between two treatments, and their estimates were highly sensitive to the amount of attrition. IPW1 and CC overestimated the absolute LDA difference between the two treatments and the overestimation increased with increasing attrition or when missingness depended on disease activity at 1 year. IPW2 and CARRAC produced unbiased estimations, but IPW2 had a greater sensitivity to the missing pattern of data and the amount of attrition than CARRAC.

Conclusions

Only multiple imputation and IPW2, which considered both confounding and treatment cessation reasons, produced accurate comparative effectiveness estimates.