Overview: comprehensive and carefully constructed strategies are required when conducting searches for adverse effects data

OBJECTIVES

Methodological research has been undertaken to investigate the many challenges in searching for adverse effects data. It is imperative that the search approach adopted in systematic reviews is based on the best available evidence. We provide a detailed summary of the results and implications of the current evidence base to assist future searches for adverse effects.

STUDY DESIGN AND SETTING

This article is a narrative review from the authors of the Cochrane Handbook chapter on adverse effects.

RESULTS

The specified search strategy must be based on the population, intervention, comparator, outcome(s) format for question formulation and appropriate study designs for adverse effects data. Search filters and suggested search terms are available for the adverse effects of drug, medical devices, and surgical interventions. The use of generic adverse effects terms (such as harms and complications) as text words and indexing terms and specific adverse effects terms (such as rash and wound infection) are warranted. Searching databases beyond MEDLINE has proven useful, as well as the use of nondatabase sources.

CONCLUSION

This article provides the most up-to-date evidence-based guidance in identifying adverse effects data in the literature. It will support searchers and researchers evaluating the potential for harm of medical interventions in systematic reviews.

Statins and risk of cataracts: A systematic review and meta-analysis of observational studies

INTRODUCTION

Two previous meta-analyses evaluated the risk of cataracts associated with statins, but did not include relevant studies suggesting a cataractogenic effect.

AIMS

The aim of this systematic review and meta-analysis of observational studies is to evaluate such association considering the latest published evidence.

METHODS

A literature search was conducted to identify observational, comparative studies evaluating the risk of developing cataracts in patients treated with statins. A meta-analysis was performed to estimate odds ratios (ORs). Results were stratified according to the following studies' subgroups: design, methodological quality, method of diagnosis of cataract, patients' age, and median follow-up. Meta-regressions evaluated the influence of the following risk factors: smoking, hypertension, corticosteroids, selective serotonin reuptake inhibitors (SSRI), diabetes mellitus, and cardiovascular disease.

RESULTS

Twenty-one studies were included. Treatment with statins was associated with an increased risk of cataracts [OR: 1.11 (95% CI: 1.02-1.21); P = 0.017; I²  = 97.5%]. This risk remained statistically significant among case-controls, good methodological quality studies, studies with length of follow-up ≥5 years and those which outcome was cataract surgery. Between-studies heterogeneity was high among all risk estimates. Meta-regressions identified an inverse relationship between the risk of cataracts and the proportion of diabetic patients in the studies.

CONCLUSIONS

The results point out an increased risk of cataract development with statins. However, since the magnitude of the effect is low and between-studies heterogeneity is high, the extent in which these results have impact on the benefit/risk ratio of statins is difficult to ascertain due to the uncertainty of the findings.

Safety of psychotropic medicines: contribution from observational evidence

The risks associated with psychotropic drugs use should be accurately documented at the population level in view of the growing number of persons exposed to these drugs. The strengths of observational studies regarding the identification of drug-related harms mirror the limitations of randomised controlled trials and vice-versa. Observational studies can be carried out in large samples of unselected participants treated in real-life conditions and who may be followed up over long periods. Serious adverse effects undetected during pre-marketing clinical trials may be observed only in post-marketing use, such as metabolic effects of second-generation antipsychotics. Observational studies play a key role in the identification of teratogenic risks, such as those induced by prenatal exposure to anticonvulsants. These studies are the main source of information to investigate the long-term effects of drugs, such as the possible increased risk of dementia in benzodiazepine users. They may also contribute to the accurate assessment at population level of risks overestimated by studies carried out in non-representative samples, such as the risk of congenital heart diseases in babies prenatally exposed to lithium. Owing to the lack of random allocation of drugs, confounding by indication or by disease severity are the major sources of biases in observational studies exploring drug safety. An adverse outcome may be wrongly imputed to drug exposure while it is a symptom/outcome of the disease motivating the decision to prescribe. Such a bias may occur in studies investigating the link between exposure to antidepressants and suicidality. As several methods have been developed to lessen the impact of such biases, pharmaco-epidemiological studies based upon stringent methodological designs should be regarded as a valid approach for assessing psychotropic drug safety.

[Hospitalizations and deaths from drug poisoning and adverse reactions in Brazil: an analysis from 2000 to 2014]

In recent years, drug poisoning and adverse reactions have been an important cause of hospitalization and mortality and a major public health issue. The aim of this study was to describe trends in hospitalizations and deaths from drug poisoning and adverse reactions from 2000 to 2014. Data were from the Mortality Information System (SIM) and Information System on Authorizations for Hospital Admissions of the Brazilian Unified National Health System (SIH-SUS), and the study population was analyzed by sex, region of residence, and age bracket. Events were defined according to ICD-10 codes. The analysis of trends in the historical series used Prais-Winsten generalized linear regression with correction for first order autocorrelation effect. Both the hospitalizations and deaths during the study period showed upward trends. The analysis by regions maintained the upward trends for both events in the South and Southeast regions. Analysis according to age brackets showed downward trends in children under five years in both events, upward trend in deaths in individuals over four years of age, and an upward trend in hospitalizations in the age bracket from 20 to 59 years. Drug poisoning and adverse reactions contribute significantly to hospitalizations and deaths in Brazil, and the SIM and SIH-SUS are data sources with satisfactory quality for population-based studies on hospital morbidity and mortality in the country.

Number needed to treat (NNT) in clinical literature: an appraisal

BACKGROUND

The number needed to treat (NNT) is an absolute effect measure that has been used to assess beneficial and harmful effects of medical interventions. Several methods can be used to calculate NNTs, and they should be applied depending on the different study characteristics, such as the design and type of variable used to measure outcomes. Whether or not the most recommended methods have been applied to calculate NNTs in studies published in the medical literature is yet to be determined. The aim of this study is to assess whether the methods used to calculate NNTs in studies published in medical journals are in line with basic methodological recommendations.

METHODS

The top 25 high-impact factor journals in the "General and/or Internal Medicine" category were screened to identify studies assessing pharmacological interventions and reporting NNTs. Studies were categorized according to their design and the type of variables. NNTs were assessed for completeness (baseline risk, time horizon, and confidence intervals [CIs]). The methods used for calculating NNTs in selected studies were compared to basic methodological recommendations published in the literature. Data were analyzed using descriptive statistics.

RESULTS

The search returned 138 citations, of which 51 were selected. Most were meta-analyses (n = 23, 45.1%), followed by clinical trials (n = 17, 33.3%), cohort (n = 9, 17.6%), and case-control studies (n = 2, 3.9%). Binary variables were more common (n = 41, 80.4%) than time-to-event (n = 10, 19.6%) outcomes. Twenty-six studies (51.0%) reported only NNT to benefit (NNTB), 14 (27.5%) reported both NNTB and NNT to harm (NNTH), and 11 (21.6%) reported only NNTH. Baseline risk (n = 37, 72.5%), time horizon (n = 38, 74.5%), and CI (n = 32, 62.7%) for NNTs were not always reported. Basic methodological recommendations to calculate NNTs were not followed in 15 studies (29.4%). The proportion of studies applying non-recommended methods was particularly high for meta-analyses (n = 13, 56.5%).

CONCLUSIONS

A considerable proportion of studies, particularly meta-analyses, applied methods that are not in line with basic methodological recommendations. Despite their usefulness in assisting clinical decisions, NNTs are uninterpretable if incompletely reported, and they may be misleading if calculating methods are inadequate to study designs and variables under evaluation. Further research is needed to confirm the present findings.

Safety profiles of iron chelators in young patients with haemoglobinopathies

BACKGROUND

This review describes the safety of deferoxamine (DFO), deferiprone (DFP), deferasirox (DFX) and combined therapy in young patients less than 25 yr of age with haemoglobinopathies.

METHODS

Searches in electronic literature databases were performed. Studies reporting adverse events associated with iron chelation therapy were included. Study and reporting quality was assessed using AHRQ Risk of Bias Assessment Tool and McMaster Quality Assessment Scale of Harms. Prospective clinical studies were pooled in a random-effects meta-analysis of proportions.

RESULTS

Safety data of 2040 patients from 34 studies were included. Ninety-two case reports of 246 patients were identified. DFX (937 patients) and DFP (667 patients) possess the largest published safety evidence. Fewer studies on combination regimens are available. Increased transaminases were seen in all regimens (3.9-31.3%) and gastrointestinal disorders with DFP and DFX (3.7-18.4% and 5.8-18.8%, respectively). Therapy discontinuations due to adverse events were low (0-4.1%). Reporting quality was selective and poor in most of the studies.

CONCLUSION

Iron chelation therapy is generally safe in young patients, and published data correspond to summary of product characteristics. Each iron chelation regimen has its specific safety risks. DFO seems not to be associated with serious adverse effects in recommended doses. In DFP and DFX, rare, but serious, adverse reactions can occur. Data on combined therapy are scarce, but it seems equally safe compared to monotherapy.

Testing the usefulness of the number needed to treat to be harmed (NNTH) in benefit-risk evaluations: case study with medicines withdrawn from the European market due to safety reasons

OBJECTIVE

To explore the usefulness of number needed to treat to be harmed (NNTH), in benefit-risk assessments, by studying the agreement between NNTH values and withdrawals of medicines from European market due to safety reasons.

METHODS

Medicines with data from longitudinal studies were included. Studies were identified from European Medicines Agency's Reports. Meta-analyses were performed to pool odds ratios (OR) with 95% confidence-intervals (CI). Published control event rates were applied to ORs to calculate NNTHs (95%CI) for selected adverse events.

RESULTS

NNTH (95%CI) decreased from pre- to post-marketing for the eight medicines included: peripheral neuropathy (∞ vs. 12[non-significant; NS] with almitrine; heart valve disease with benfluorex (∞ vs. NNTH ranging from 7[4-13] to 7[5-9]); myopathy (-4096[NS] vs. 797[421-1690]), new-onset diabetes (113[NS] vs. 390[425-778]), bleeding (∞ vs. 517[317-1153]), and infection (∞ vs. 253[164-463]) with niacin-laropiprant; psychiatric disorders (12[7-34] vs. 9[5-24]) with rimonabant; myocardial infarction (MI) [-1305 vs. 270[89-4362]) with rofecoxib; MI (-510 vs. NNTH ranging from 152[55-4003] to 568[344-1350]) with rosiglitazone; cardiovascular events (∞ vs. 245[129-1318]) with sibutramine; and liver injury (∞ vs. 5957[NS]) with ximelagatran.

CONCLUSION

NNTH have potential of use as a supportive tool in benefit-risk re-evaluations of medicines and may help regulators to making decisions on drug safety.

Challenges and opportunities in measuring cancer recurrence in the United States

Cancer recurrence and disease-free survival are key outcomes for measuring the burden of illness, assessing the quality of cancer care, and informing decisions about increasingly costly cancer therapies. Yet information about recurrence is not collected in cancer registries or other population-based data sources. To address the lack of population-based recurrence information, researchers are increasingly using algorithms applied to health claims to infer recurrence. However, the validity of these approaches has not been comprehensively evaluated. In this commentary, we review existing studies and discuss options for improving the availability of recurrence data. We found that the validity of claims-based approaches appears promising in small, single institution studies, but larger population-based studies have identified substantial limitations with using claims to identify recurrence. With the increasing availability of health data, there are potential options that can be implemented to enhance information about recurrence. These options include design of software for the electronic medical record that enables rapid and standardized reporting of recurrence, use of electronic pathology reports to facilitate streamlined collection of recurrence by cancer registries, and mandates by insurers to require reporting of recurrence on health claims submitted by physicians. All of these options will require that governmental agencies, health insurers, professional societies, and other groups recognize the importance of population-based recurrence data and determine that this information is a priority for assessing cancer outcomes and costs.

Comparison of search strategies in systematic reviews of adverse effects to other systematic reviews

BACKGROUND

Research indicates that the methods used to identify data for systematic reviews of adverse effects may need to differ from other systematic reviews.

OBJECTIVES

To compare search methods in systematic reviews of adverse effects with other reviews.

METHODS

The search methodologies in 849 systematic reviews of adverse effects were compared with other reviews.

RESULTS

Poor reporting of search strategies is apparent in both systematic reviews of adverse effects and other types of systematic reviews. Systematic reviews of adverse effects are less likely to restrict their searches to MEDLINE or include only randomised controlled trials (RCTs). The use of other databases is largely dependent on the topic area and the year the review was conducted, with more databases searched in more recent reviews. Adverse effects search terms are used by 72% of reviews and despite recommendations only two reviews report using floating subheadings.

CONCLUSIONS

The poor reporting of search strategies in systematic reviews is universal, as is the dominance of searching MEDLINE. However, reviews of adverse effects are more likely to include a range of study designs (not just RCTs) and search beyond MEDLINE.

Reporting of meta-analyses of randomized controlled trials with a focus on drug safety: An empirical assessment

Background

Due to the sparse nature of serious drug-related adverse events (AEs), meta-analyses combining data from several randomized controlled trials (RCTs) to evaluate drug safety issues are increasingly being conducted and published, influencing clinical and regulatory decision making. Evaluation of meta-analyses involves the assessment of both the individual constituent trials and the approaches used to combine them. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting framework is designed to enhance the reporting of systematic reviews and meta-analyses. However, PRISMA may not cover all critical elements useful in the evaluation of meta-analyses with a focus on drug safety particularly in the regulatory-public health setting.

Purpose

This work was conducted to (1) evaluate the adherence of a sample of published drug safety–focused meta-analyses to the PRISMA reporting framework, (2) identify gaps in this framework based on key aspects pertinent to drug safety, and (3) stimulate the development and validation of a more comprehensive reporting tool that incorporates elements unique to drug safety evaluation.

Methods

We selected a sample of meta-analyses of RCTs based on review of abstracts from high-impact journals as well as top medical specialty journals between 2009 and 2011. We developed a preliminary reporting framework based on PRISMA with specific additional reporting elements critical for the evaluation of drug safety meta-analyses of RCTs. The reporting of pertinent elements in each meta-analysis was reviewed independently by two authors; discrepancies in the independent evaluations were resolved through discussions between the two authors.

Results

A total of 27 meta-analyses, 12 from highest impact journals, 13 from specialty medical journals, and 2 from Cochrane reviews, were identified and evaluated. The great majority (>85%) of PRISMA elements were addressed in more than half of the meta-analyses reviewed. However, the majority of meta-analyses (>60%) did not address most (>80%) of the additional reporting elements critical for the evaluation of drug safety. Some of these elements were not addressed in any of the reviewed meta-analyses.

Limitations

This review included a sample of meta-analyses, with a focus on drug safety, recently published in high-impact journals; therefore, we may have underestimated the extent of the reporting problem across all meta-analyses of drug safety. Furthermore, temporal trends in reporting could not be evaluated in this review because of the short time interval selected.

Conclusions

While the majority of PRISMA elements were addressed by most studies reviewed, the majority of studies did not address most of the additional safety-related elements. These findings highlight the need for the development and validation of a drug safety reporting framework and the importance of the current initiative by the Council for International Organizations of Medical Sciences (CIOMS) to create a guidance document for drug safety information synthesis/meta-analysis, which may improve reporting, conduct, and evaluation of meta-analyses of drug safety and inform clinical and regulatory decision making.

Thiazolidinedione use and cancer incidence in type 2 diabetes: a systematic review and meta-analysis

AIMS

Evidence suggests thiazolidinediones (TZDs) may modify the relationship between type 2 diabetes and cancer incidence. We aimed to summarize data from randomized controlled trials (RCTs) and observational studies to examine risk of overall and site-specific cancers with TZD use in individuals with type 2 diabetes.

METHODS

We searched 12 key biomedical databases and seven grey literature sources up to June 2011, without language restrictions. We performed separate meta-analyses according to cancer site and study design, comparing ever-use to never-use of TZDs, and pioglitazone alone.

RESULTS

The search yielded 1338 unique citations; we included four RCT, seven cohort and nine nested case-control studies, contributing data from 2.5 million people. Estimates from observational studies suggested any TZD use was associated with a decreased risk of colorectal (pooled RR: 0.93, 95%CI 0.87-1.00, P=0.04, I(2)=30%), lung (pooled RR: 0.91, 95%CI 0.84-0.98, P=0.02, heterogeneity (I(2))=35%) and breast (pooled RR: 0.89, 95%CI 0.81-0.98, P=0.02, I(2)=44%) cancer. Risk of overall cancer with TZD use was not significantly modified in RCTs (pooled RR: 0.92, 95%CI 0.79-1.07, P=0.26, I(2)=0%) or observational studies (pooled OR: 0.95, 95%CI 0.78-1.16, P=0.63, I(2)=70%). Pioglitazone use was, however, associated with a decreased risk of overall cancer (colorectal, lung, breast, prostate and renal sub-sites combined) in observational studies (pooled RR: 0.95, 95%CI 0.91-0.99, P=0.009, I(2)=0%).

CONCLUSIONS

Our findings suggest that use of TZDs is associated with a modest but significantly decreased risk of lung, colorectal and breast cancers. Results were limited by the paucity of studies designed to answer our research question. Further evaluation of TZD use, cancer risk factors and potential confounders is required.