Summarising the Evidence for Drug Safety: A Methodological Discussion of Different Meta-Analysis Approaches

Evidence on drug safety obtained from randomised clinical trials is very limited due to, among other reasons, their relatively small sample size. Hence, combining the results of available studies can prove particularly useful. This paper reviews the different data sources for summarising drug safety outcomes, according to study design, publication of data, and origin of the information. It then discusses the various types of overviews that can be used in the study of treatment harms, focusing on meta-analyses of aggregate data and meta-analyses of individual patient data, with their advantages and drawbacks, such as publication bias and heterogeneity. Although the different approaches available for combining the results are of great utility in assessing treatment harms, none of them is free from limitations. Therefore, it might be appropriate to perform an analysis of sensitivity to assess whether the results are sensitive to the technique that has been used.

Review of quality assessment tools for the evaluation of pharmacoepidemiological safety studies

OBJECTIVES

Pharmacoepidemiological studies are an important hypothesis-testing tool in the evaluation of postmarketing drug safety. Despite the potential to produce robust value-added data, interpretation of findings can be hindered due to well-recognised methodological limitations of these studies. Therefore, assessment of their quality is essential to evaluating their credibility. The objective of this review was to evaluate the suitability and relevance of available tools for the assessment of pharmacoepidemiological safety studies.

DESIGN

We created an a priori assessment framework consisting of reporting elements (REs) and quality assessment attributes (QAAs). A comprehensive literature search identified distinct assessment tools and the prespecified elements and attributes were evaluated.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was the percentage representation of each domain, RE and QAA for the quality assessment tools.

RESULTS

A total of 61 tools were reviewed. Most tools were not designed to evaluate pharmacoepidemiological safety studies. More than 50% of the reviewed tools considered REs under the research aims, analytical approach, outcome definition and ascertainment, study population and exposure definition and ascertainment domains. REs under the discussion and interpretation, results and study team domains were considered in less than 40% of the tools. Except for the data source domain, quality attributes were considered in less than 50% of the tools.

CONCLUSIONS

Many tools failed to include critical assessment elements relevant to observational pharmacoepidemiological safety studies and did not distinguish between REs and QAAs. Further, there is a lack of considerations on the relative weights of different domains and elements. The development of a quality assessment tool would facilitate consistent, objective and evidence-based assessments of pharmacoepidemiological safety studies.

Secondary use of randomized controlled trials to evaluate drug safety: a review of methodological considerations

Background Randomized clinical trials (RCTs) are often positioned at the top of evidence hierarchies. Meta-analyses of RCTs aim to integrate the state of knowledge on a given scientific question, particularly for rare drug-related outcomes. However, although RCTs are valuable tools in our armamentarium, they are rarely designed to evaluate drug safety and are thus susceptible to limitations that may hamper the ability of both RCTs and meta-analyses to fully characterize the safety profiles of drugs. Their potential limitations might be exacerbated in the study of rare outcomes, often encountered in drug safety assessment, when even minor deviations from the intended randomization could impact the stability of the risk estimates.

Purpose This article considers the methodological caveats of both RCTs and meta-analyses of RCTs pertinent to the study of drug-related harms. It is intended to stimulate discussion about the impact of these caveats on interpreting findings of RCTs and meta-analyses for drug safety, which would foster more robust, critical evaluations, and thus enhance clinical and regulatory decision-making.

Methods Pertinent issues that can influence the interpretation of drug-related harms discussed in this article were based on authors’ expertise and review of the literature.

Results Investigators and clinicians should be cognizant of the potential limitations of the secondary use of RCTs and meta-analyses in the assessment of drug-related harms and, when applicable, should consider potential remedies to overcome these limitations.

Limitations Only few practical examples are included in the article due to the fact that many of the discussed caveats are not examined and/or reported in many publications. In addition, the confidential nature of data reviewed at a regulatory agency forestalls an in depth discussion of examples pertaining to specific drugs. Furthermore, our ability to quantify the extent of encountering, or the actual impact of, the caveats addressed in this review on the RCTs findings is limited. It is worth noting that the mere encounter of a given caveat does not mean that it will obviate the utility of drug safety information from a given trial. The extent of its impact is expected to vary based on the specifics of the trial, the drugs studied, the indications, and the nature of the adverse events.

Conclusions Although some of the limitations described are inherent in RCTs, some of the sources of bias highlighted in this article could be minimized by careful RCT design, planned follow-up, and improved collection of information on adverse events. As future research sheds more light on pertinent knowledge gaps and issues, the ability to maximize the use of RCTs and meta-analyses of RCTs to address drug safety questions of interest will be greatly enhanced.

Clinical safety of tocilizumab in rheumatoid arthritis

IMPORTANCE OF THE FIELD

Tocilizumab is a new biologic disease-modifying antirheumatic drug directed against the activity of IL-6, a key pro-inflammatory cytokine in the pathogenesis of rheumatoid arthritis (RA). This drug has proved highly effective in RA patients, including those who had previously not responded to anti-TNFs. As side effects are a major cause for discontinuing biologic therapy, the present article focuses on the tolerability profile of tocilizumab.

AREAS COVERED IN THIS REVIEW

This review describes the adverse events (AEs) reported in RA patients treated with tocilizumab. Most data are derived from controlled clinical trials and their open-label extensions.

WHAT THE READER WILL GAIN

The reader will gain a comprehensive review of treatment-emergent AEs associated with tocilizumab therapy. These AEs include infections, including opportunistic infections, infusion and hyper-sensitivity reactions, gastrointestinal perforation, and laboratory test abnormalities, especially hepatic transaminase elevations, altered lipid profile and neutropenia.

TAKE HOME MESSAGE

Based on current data, tocilizumab appears to have an acceptable safety profile inasmuch as most AEs were manageable or controllable. However, results from large scale pharmacoepidemiological investigations and appropriate post-marketing surveillance are awaited to identify the full spectrum of AEs and define the true benefit:risk ratio of tocilizumab.