Pharmacovigilance: a science or fielding emergencies?

Thromboembolism and Oral Contraceptives During the COVID-19 Pandemic: A Disproportionality Analysis Within the Spanish Pharmacovigilance Database

Background

Thromboembolic events (TEs) are known to be a severe complication for COVID-19. They are associated with a systemic inflammatory response syndrome with coagulation cascade activation.

Objective

The aim of this study was to determine a potential association between the COVID-19 pandemic and the increment of the risk of suspected TEs in women on systemic hormonal contraceptives (SHCs).

Patients and Methods

This study utilised a case/non-case approach in the Spanish Pharmacovigilance Database, which includes more than 290,000 cases of suspected adverse drug reactions (ADRs). The reporting odds ratio (ROR) was calculated during an initial pandemic period in 2020 compared with a pre-pandemic period in 2019 and an additional control period in 2018.

Results

While there was a decreased number of ADR notifications for any medications and for any type of ADR in patients on SHCs during the pandemic period, the TE ROR for all SHCs was higher in the 2020 pandemic period [ROR = 11.8 (5.6–24.7)] relative to the pre-pandemic period in 2019 [ROR = 6.3 (3.2–12.5)] and the additional control period in 2018 [ROR = 4.6. (2.1–9.9)]. In contrast, ROR for progestogen-only contraceptives was lower during the pandemic as compared with the two control periods.

Conclusion

The reported disproportionality of TEs in women on SHCs rose during the pandemic period. This suggests a potential interaction of the drug (SHC) with COVID-19, which led to an increased risk of TEs in women exposed to both factors. This should be taken into consideration in the context of the COVID-19 pandemic.

Risk of bronchospasm and coronary arteriospasm with sugammadex use: a post marketing analysis

Introduction:

Sugammadex is used for the reversal of neuromuscular blockade caused by rocuronium bromide and vecuronium bromide. As part of the post licensing phase of drug development, adverse events related to the use of sugammadex are still being uncovered and being reported. The potential association between sugammadex and adverse events bronchospasm and coronary arteriospasm using a retrospective pharmacovigilance signal analysis was carried out.

Methods:

Food and Drug Administration’s Adverse Event Reporting System database was used to run disproportionality analyses to investigate the potential association of sugammadex with bronchospasm or coronary arteriospasm. In this analysis we report the adverse event signal using frequentist methods of Relative reporting ratio (RRR), proportional reporting ratio (PRR), reporting odds ratio (ROR) and the Bayesian based Information Component metric.

Results:

A statistically significant disproportionality signal is found between sugammadex and bronchospasm (n = 44; chi-squared = 2993.87; PRR = 71.95 [95% CI: 54.00–95.85]) and sugammadex and coronary arteriospasm (n = 6; chi-squared = 209.39; PRR = 43.82 [95% CI: 19.73–97.33]) as per Evans criteria. Both statistically significant disproportionality signals persisted when stratified by gender. Based upon dynamic cumulative PRR graph, the PRR value has steadily increased and the 95% CI narrowed since December 2012.

Conclusion:

The results of the pharmacovigilance analysis highlight a statistically significant disproportionality signal between sugammadex usage and bronchospasm and coronary arteriospasm adverse events. Physicians need to be aware of these adverse events when using sugammadex. The results of the pharmacovigilance signal analysis highlight a statistically significant disproportionality signal between sugammadex usage and bronchospasm and coronary arteriospasm adverse events. Physicians need to be aware of these adverse events when using sugammadex.

Sensitivity of Quantitative Signal Detection in Regards to Pharmacological Neuroenhancement

Pharmacological neuroenhancement (PNE) is a form of abuse and has not yet been addressed by methods of pharmacovigilance. In the present study, we tested if quantitative signal detection may be sensitive in regards to PNE. We evaluated the risk of drug abuse and dependence (DAAD) related to substances that are known to be used for PNE and divided this group into agents with (methylphenidate) and without a known abuse potential outside the field of PNE (atomoxetine, modafinil, acetylcholine esterase inhibitors, and memantine). Reporting odds ratios (RORs) were calculated using a case/non-case approach based on global and country-specific drug safety data from the Uppsala Monitoring Centre (UMC). Both control substances (diazepam and lorazepam) and methylphenidate were statistically associated with DAAD in all datasets (except methylphenidate in Italy). Modafinil was associated with DAAD in the total dataset (ROR, 2.7 (95% confidence interval (CI), 2.2-3.3)), Germany (ROR, 4.6 (95% CI, 1.8-11.5)), and the USA (ROR, 2.0 (95% CI, 1.6-2.5)). Atomoxetine was associated with DAAD in the total dataset (ROR, 1.3 (95% CI, 1.2-1.5)) and in the UK (ROR, 3.3 (95% CI, 1.8-6.1)). Apart from memantine, which was associated with DAAD in Germany (ROR, 1.8 (95% CI, 1.0-3.2)), no other antidementia drug was associated with DAAD. Quantitative signal detection is suitable to detect agents with a risk for DAAD. Its sensitivity regarding PNE is limited, although atomoxetine and modafinil, which do not have a known abuse potential outside PNE, and no antidementia drugs, whose use in PNE is presumably low, were associated with DAAD in our analysis.

Association between haemorrhages and treatment with selective and non-selective serotonergic antidepressants: Possible implications of quantitative signal detection

Inhibition of serotonin uptake in platelets seems to be the crucial mechanism underlying SSRI-associated haemorrhages. This effect is also present in antidepressants featuring non-selective serotonin reuptake inhibition (non-SSRI). Impact of selectivity of serotonin reuptake and/or affinity to the serotonin reuptake transporter on the bleeding risk have not yet been studied sufficiently. We retrieved country- and SSRI-/non-SSRI-specific data from the Uppsala Monitoring Centre and used a case/non-case approach to calculate substance-specific reporting odds ratios (ROR) to evaluate the statistical association of treatment with SSRI/non-SSRI and haemorrhages. Country-specific analysis revealed no clear trends towards an increased risk of bleeding related to particular agents of group SSRI/non-SSRI (sporadically ROR>1 for citalopram, duloxetine, escitalopram, fluvoxamine, paroxetine, sertraline, St. John's wort). There was a clear trend in the total dataset towards a "reduced protective effect" (suggested by ROR<1) on the development of haemorrhages with agents featuring comparatively high affinity to the 5-HTT and/or selective serotonin reuptake inhibition (as with escitalopram, citalopram, duloxetine or venlafaxine) in comparison to agents with lower affinity or non-selective serotonin reuptake inhibition (as with mirtazapine or doxepin). Comparison of group-specific aggregated data (SSRI vs. non-SSRI) revealed significant differences regarding the "protective effect" on the development of haemorrhages between groups SSRI vs. non-SSRI in favour of non-SSRI in nearly all countries as well as in the total dataset. Our findings provide preliminary evidence that agents with increased affinity to the 5-HTT and/or selective serotonin reuptake inhibition may be associated with an increased risk of bleeding.

Hepatotoxicity associated with agomelatine and other antidepressants: Disproportionality analysis using pooled pharmacovigilance data from the Uppsala Monitoring Centre

Since its marketing approval, the attention to the hepatic side-effect profile of the antidepressant agomelatine (AGM) has gradually increased. Several cases of severe hepatotoxic adverse drug reactions (ADR) have been reported and the European Medicines Agency has released a safety warning regarding AGM-associated hepatotoxicity. However, there are insufficient data for an adequate safety assessment of AGM-related hepatotoxicity. Therefore, we performed a quantitative signal detection analysis using pharmacovigilance data from the Uppsala Monitoring Centre from the WHO that records ADR data from worldwide sources; we calculated reporting odds ratios (ROR) as measures for disproportionality within a case/non-case approach for AGM and several other antidepressants. AGM was statistically associated with an increased risk of hepatotoxicity (ROR 6.4 [95%CI 5.7-7.2]) as well as both positive controls: amineptine (ROR 38.4 [95%CI 33.8-43.6]) and nefazodone (ROR 3.2 [95%CI 3.0-3.5]). Following amineptine, AGM was associated with the second highest ROR, followed by tianeptine (ROR 4.4 [95%CI 3.6-5.3]), mianserin (ROR 3.6 [95%CI 3.3-3.9]), and nefazodone. These results support the hypothesis that AGM is associated with relevant hepatotoxicity. However, the used data and applied method do not allow a quantitative evaluation of hepatotoxicity or assessment of substance-specific differences regarding the extent of hepatotoxicity.

Tuberculosis risk and anti-tumour necrosis factor agents in rheumatoid arthritis: a critical appraisal of national registry data

Tuberculosis (TB) remains a major global health problem. In patients with rheumatoid arthritis (RA), the risk of reactivation of latent TB infection (LTBI) is increased and treatment with tumour necrosis factor (TNF) antagonists further increases this risk. However, interpretation of results describing comparative TB risk during therapy with different TNF antagonists is difficult. This is not only a result of different patient ethnic groups and background TB rates, but also because of differing methods of data acquisition. This paper offers a critical appraisal of registry data pertaining to RA patients treated with different anti-TNF agents, focusing on methodological approaches that may limit the generalizability of findings or invalidate the direct comparison of TB risk between different national registries. Underlying factors that can make data interpretation challenging are discussed, including differences in methods for TB diagnosis or data collection and reporting, as well as background TB risk. The introduction of special monitoring systems, such as prospective multinational registries, to strengthen surveillance and better quantify the extent of under-reporting is required, especially in countries where the background TB risk is high.

Drug Fever: a descriptive cohort study from the French national pharmacovigilance database

BACKGROUND

Although known as a rare adverse drug reaction (ADR), drug fever (DF) remains an important issue in medicine, with the risk of leading to inappropriate and potentially harmful diagnostic and therapeutic interventions. Only sparse data regarding DF have been published.

OBJECTIVE

The aim of the study was to investigate which drugs were associated with DF, and report outcomes.

METHODS

Cases of DF without skin reactions were selected from all ADRs reported from 1986 to 2007 in the French National Pharmacovigilance Database. Drugs potentially responsible for DF were assessed using a qualitative case-by-case analysis (Naranjo's criteria) and quantitative measurement (proportional reporting ratio [PRR]). A drug was implicated as the cause of DF when the following criteria were validated: three or more cases and PRR of at least two with a Chi-squared value of at least four.

RESULTS

A total of 167 DF cases involving 115 drugs were eligible. Based on the PRR, 22 drugs were significantly associated with DF. Antibacterials represented the most frequently reported drugs, including amikacin (PRR 39.6 [95% CI 23.6, 69.0], oxacillin (9.1 [3.6, 23.4]), cefotaxime (5.5 [2.0, 15.3]), ceftriaxone (5.4 [2.6, 11.3]), rifampicin (4.0 [1.8, 9.2]), vancomycin (4.0 [1.4, 11.5]), ciprofloxacin (3.1 [1.2, 8.0]), isoniazid (3.9 [1.4, 11.4]), pristinamycin (3.1 [1.0, 9.1]) and cotrimoxazole (2.6 [1.2, 5.8]). Median time [interquartile range] from drug administration to fever onset was 2 days [1.0-10.5]. A diagnosis of DF was made following cessation of the suspected drugs (3 days [1.0-11.5] after fever onset. Drug rechallenge was performed (38.0%), resulting in recurrence of DF in all cases. DF resulted in life-threatening events (0.6%), hospitalization or prolonged hospital stay (24.5%) and persistent disability (0.6%). Final outcome was favourable in 96.9% of cases after drug discontinuation.

CONCLUSION

Diagnosing DF is challenging. Based on this large series, antibacterials remain the major class of drugs responsible for DF.

Mining pharmacovigilance data using Bayesian logistic regression with James-Stein type shrinkage estimation

Spontaneous adverse event reporting systems are widely used to identify adverse reactions to drugs following their introduction into the marketplace. In this article, a James-Stein type shrinkage estimation strategy was developed in a Bayesian logistic regression model to analyze pharmacovigilance data. This method is effective in detecting signals as it combines information and borrows strength across medically related adverse events. Computer simulation demonstrated that the shrinkage estimator is uniformly better than the maximum likelihood estimator in terms of mean squared error. This method was used to investigate the possible association of a series of diabetic drugs and the risk of cardiovascular events using data from the Canada Vigilance Online Database.

Development of a therapeutics curriculum to enhance knowledge of fourth-year medical students about clinical uses and adverse effects of drugs

BACKGROUND

Enhanced clinical pharmacology and therapeutics education of medical students is important for improving effective and safe drug therapy. Increased education about pharmacovigilance is needed because serious drug-induced adverse effects are increasing. Fostering the needed scientific approach to prescribing requires knowledge of evidence-based drug therapy, based on understanding clinical trials. Therapeutic agents with novel mechanisms of action are increasingly available, and an unbiased understanding of the risks and benefits of novel agents is also important. These issues can be addressed in clinical pharmacology courses. However, many medical schools lack sufficient clinical pharmacologists to teach such courses. The Southern Illinois University Medical School faculty implemented an Advanced Therapeutics course to address these issues.

DESCRIPTION

Development of this course involved defining appropriate content and organizing preclinical pharmacology and clinical faculty into teaching teams. The course was offered to 4th-year medical students and covered clinical trial information, and cutting-edge therapeutic developments. The "ABCs of Pharmacology" is a mental algorithm that was presented in the sophomore year and reintroduced in this course. This algorithm emphasizes pharmacovigilance, which stresses the balance between positive and negative effects of pharmacological agents. General principles of clinical pharmacology and therapeutics were covered by a clinical pharmacologist. Most sessions on specific disease treatment involved an integrated presentation by a preclinical pharmacologist and a clinician with expertise in that topic, often in the context of clinical cases. Other important topics were emphasized, which reinforce individualization of therapy, including pharmacogenomics that may determine idiosyncratic responses. Feedback during and following the course was obtained via questionnaires.

EVALUATION

This approach was well received by participating students and graduates. Most students rated this course as a valuable experience.

CONCLUSION

This approach appears useful for educating medical students about therapeutics at medical schools that lack sufficient clinical pharmacology faculty to mount such a course.

Heart rhythm disturbances associated with rupatadine: a case series from the Spanish and Portuguese pharmacovigilance systems

We searched the Spanish and Portuguese pharmacovigilance databases for spontaneous case reports of heart rhythm disturbances associated with rupatadine and other new H1 antihistamines. Five cases were found involving patients treated with rupatadine (13.9% of all reports relating to this drug). In all five cases, the reaction started after exposure and resolved when the drug was discontinued. In two cases, rupatadine was the only medication being taken by the patient, and no other condition that could explain the heart rhythm disturbances was diagnosed. The reporting odds ratio was 3.2 (95% confidence interval, 1.0-10.5). The reporting rate was 2 cases per 100,000 patients treated per year (95% confidence interval, 0.4-6.0). These results suggest a causal relationship between rupatadine and heart rhythm disturbances.

Gynaecomastia associated with proton pump inhibitors: a case series from the Spanish Pharmacovigilance System

OBJECTIVE

Proton pump inhibitors (PPIs) are widely used in the management of peptic ulcer and related symptoms. They have been linked to certain endocrine adverse reactions, including gynaecomastia. The aim of the present study is to investigate the association between the use of PPIs and the development of gynaecomastia.

METHODS

Reports of cases of gynaecomastia that had putatively been induced by PPIs and that had been collected by the Spanish Pharmacovigilance System via the 'yellow card' scheme, were analysed. Reporting odds ratios (RORs) were calculated as a measure of disproportionality.

RESULTS

Twenty-four cases of gynaecomastia associated with PPIs were identified in the database of the Spanish Pharmacovigilance System. Overall, there was a clear temporal sequence of events in all cases and the adverse effect disappeared after drug withdrawal in most of the cases; 14 patients were also receiving other drugs at the time of the adverse effect. The ROR for omeprazole exposure versus no exposure, but not that for other PPIs, showed a statistically significant elevation (ROR adjusted for age 5.23; 95% CI 3.32, 8.26).

CONCLUSION

Considering the widespread use of PPIs, gynaecomastia may affect a large number of patients. In most cases, the condition seems to be reversible with drug withdrawal. Doctors should be aware of this potential adverse reaction when prescribing PPIs to their patients over long periods of time.

Extending the methods used to screen the WHO drug safety database towards analysis of complex associations and improved accuracy for rare events

Post-marketing drug safety data sets are often massive, and entail problems with heterogeneity and selection bias. Nevertheless, quantitative methods have proven a very useful aid to help clinical experts in screening for previously unknown associations in these data sets. The WHO international drug safety database is the world's largest data set of its kind with over three million reports on suspected adverse drug reaction incidents. Since 1998, an exploratory data analysis method has been in routine use to screen for quantitative associations in this data set. This method was originally based on large sample approximations and limited to pairwise associations, but in this article we propose more accurate credibility interval estimates and extend the method to allow for the analysis of more complex quantitative associations. The accuracy of the proposed credibility intervals is evaluated through comparison to precise Monte Carlo simulations. In addition, we propose a Mantel-Haenszel-type adjustment to control for suspected confounders.

Sequential genome-wide association studies for monitoring adverse events in the clinical evaluation of new drugs

Pharmacovigilance, the monitoring of adverse events (AEs), is an integral part in the clinical evaluation of a new drug. Until recently, attempts to relate the incidence of AEs to putative causes have been restricted to the evaluation of simple demographic and environmental factors. The advent of large-scale genotyping, however, provides an opportunity to look for associations between AEs and genetic markers, such as single nucleotides polymorphisms (SNPs). It is envisaged that a very large number of SNPs, possibly over 500,000, will be used in pharmacovigilance in an attempt to identify any genetic difference between patients who have experienced an AE and those who have not. We propose a sequential genome-wide association test for analysing AEs as they arise, allowing evidence-based decision-making at the earliest opportunity. This gives us the capability of quickly establishing whether there is a group of patients at high-risk of an AE based upon their DNA. Our method provides a valid test which takes account of linkage disequilibrium and allows for the sequential nature of the procedure. The method is more powerful than using a correction, such as Sidák, that assumes that the tests are independent.

Adverse reactions induced by NSAIDs and antibacterials: analysis of spontaneous reports from the Sicilian regional database

OBJECTIVES

To (i) evaluate the suspected adverse drug reactions (ADRs) related to NSAIDs and antibacterials that were reported to Sicilian local health officers by healthcare professionals; and (ii) to detect new or serious potential signals of alarm related to these two widely used drug categories.

METHODS

We selected all the spontaneous reports of ADRs sent between January 1998 and June 2004 and analysed those attributed to NSAIDs and systemic antibacterials, applying proportional reporting ratio (PRR) methodology. PRRs >2, chi(2) >4 and >3 ADRs were regarded as signals.

RESULTS

During the period considered, 1585 reports of ADRs were received overall (42.6% serious), with an annual reporting rate of approximately 49.1 reports per million inhabitants on average; 351 referred to systemic antibacterials, and 179 to NSAIDs. There were 174 (49.6%) reports of serious ADRs associated with antimicrobials and 108 (60.3%) associated with NSAIDs. Disproportionality was observed, in particular for anaphylactic shock induced by ceftriaxone (all reports were associated with off-label use of the drug), photosensitivity reaction induced by lomefloxacin (administered in the summer), hepatitis induced by nimesulide (three cases leading to liver transplantation) and vasculitis induced by nimesulide.

CONCLUSION

Our analysis highlighted several signals of alarm deserving further investigation or measures to influence prescribing. This study underlines the value of a regional centre in identifying local factors (such as prescribing patterns) that may increase the prevalence of serious ADRs.

National differences in reporting 'pneumonia' and 'pneumonia interstitial': an analysis of the WHO International Drug Monitoring Database on 15 drugs in nine countries for seven pulmonary conditions

PURPOSE

Increased post-marketing reports of 'interstitial pneumonia' as an adverse drug reaction (ADR) from the use of gefitinib, irinotecan, or leflunomide among patients in Japan have not been noted in other countries. The WHO International Drug Monitoring Database was analyzed to examine Japan's pattern of reporting the term 'pneumonia interstitial' for 15 selected drugs with a mixed history of association with pulmonary ADRs.

METHODS

ADR counts from the WHO Database for 1992-2001 were obtained for 15 disparate drugs (three androgen blockers, eight cytotoxics, one proton pump inhibitor, one monoclonal antibody, and two anti-epileptics) from nine countries (Australia, France, Germany, Italy, Japan, Spain, Thailand, U.K., and U.S.A.) for seven pulmonary ADR terms (alveolitis fibrosing, pneumonia, pulmonary fibrosis, lung fibrosis interstitial, pulmonary infiltration, interstitial lung disease, and pneumonia interstitial). Statistical analyses included estimating Poisson-distributed expected rates, observed/expected (O/E) ratios, and 95% confidence intervals (CI). The overlapping nature and changes in definition over time of these terms in medical texts and in the WHO-ART, COSTART, J-ART, and MedDRA coding systems is also noted.

RESULTS

Compared to other countries, both Japan and France did not have higher O/E reporting ratios for all seven pulmonary ADRs combined, but did have higher O/E ratios for 'pneumonia interstitial' and lower O/E ratios for 'pneumonia' for the same drugs.

CONCLUSIONS

Japan and France were found to preferentially use the term 'pneumonia interstitial' for ADR where other countries used 'pneumonia.' This cultural pattern coincides with the fact that 'pneumonia interstitial' in older versions of COSTART, J-ART, and MedDRA were subsumed under infectious pulmonary diseases.

Perspectives on the use of data mining in pharmaco-vigilance

In the last 5 years, regulatory agencies and drug monitoring centres have been developing computerised data-mining methods to better identify reporting relationships in spontaneous reporting databases that could signal possible adverse drug reactions. At present, there are no guidelines or standards for the use of these methods in routine pharmaco-vigilance. In 2003, a group of statisticians, pharmaco-epidemiologists and pharmaco-vigilance professionals from the pharmaceutical industry and the US FDA formed the Pharmaceutical Research and Manufacturers of America-FDA Collaborative Working Group on Safety Evaluation Tools to review best practices for the use of these methods.In this paper, we provide an overview of: (i) the statistical and operational attributes of several currently used methods and their strengths and limitations; (ii) information about the characteristics of various postmarketing safety databases with which these tools can be deployed; (iii) analytical considerations for using safety data-mining methods and interpreting the results; and (iv) points to consider in integration of safety data mining with traditional pharmaco-vigilance methods. Perspectives from both the FDA and the industry are provided. Data mining is a potentially useful adjunct to traditional pharmaco-vigilance methods. The results of data mining should be viewed as hypothesis generating and should be evaluated in the context of other relevant data. The availability of a publicly accessible global safety database, which is updated on a frequent basis, would further enhance detection and communication about safety issues.

Risk and case characteristics of tuberculosis in rheumatoid arthritis associated with tumor necrosis factor antagonists in Sweden

OBJECTIVE

Because treatment with tumor necrosis factor (TNF) antagonists may increase the risk of tuberculosis (TB), and because knowledge of the risk of TB in rheumatoid arthritis (RA) not treated with biologics is scarce and of uncertain generalizability to low-risk populations, this study sought to determine the risk of TB among Swedish patients with RA.

METHODS

Using data from Swedish nationwide and population-based registers and data from an ongoing monitoring program of TNF antagonists, the relative risks of TB in patients with RA (versus the general population) and of TB associated with TNF antagonists (versus RA patients not treated with biologics) were determined by comparing the incidence of hospitalization for TB in 3 RA cohorts and 2 general population cohorts from 1999 to 2001. We also reviewed the characteristics of all reported cases of TB in RA patients treated with TNF antagonists in Sweden and calculated the incidence of TB per type of TNF antagonist between 1999 and 2004.

RESULTS

During 1999-2001, RA patients who were not treated with TNF antagonists were at increased risk of TB versus the general population (relative risk 2.0, 95% confidence interval [95% CI] 1.2-3.4). RA patients treated with TNF antagonists had a 4-fold increased risk of TB (relative risk 4.0, 95% CI 1.3-12) versus RA patients not treated with TNF antagonists. The reported TB cases during 1999-2004 in RA patients exposed to TNF antagonists (9 infliximab, 4 etanercept, 2 both) were predominantly pulmonary. TB occurred up to 3 years following the start of treatment.

CONCLUSION

Irrespective of whether TNF antagonists are administered, Swedish patients with RA are at increased risk of TB. During 1999-2001, TNF antagonists were associated with an increased risk of TB, up to 4-fold in magnitude. This increased risk may persist over time during treatment and is related to both infliximab and etanercept.

An analysis of rotavirus vaccine reports to the vaccine adverse event reporting system: more than intussusception alone?

BACKGROUND

The rhesus-human rotavirus reassortant-tetravalent vaccine (RRV-TV) was licensed on August, 31, 1998, and subsequently recommended for routine infant immunizations in the United States. After approximately 1 million doses had been administered, an increase in acute risk of intussusception in vaccinees led to the suspension of the use of RRV-TV and its withdrawal from the market. These postmarketing safety studies focused on a single adverse event (intussusception) and, to minimize the risk of a false-positive finding, accepted only cases that met a strict case definition. Safer rotavirus vaccines are needed to prevent the substantial global morbidity and mortality caused by rotavirus infections; their development and future use may benefit from a better understanding of the postmarketing safety profile of RRV-TV beyond intussusception.

OBJECTIVE

To characterize more completely the postmarketing surveillance safety profile of RRV-TV more completely by review and analysis of Vaccine Adverse Event Reporting System (VAERS) case reports to better understand 1) whether severe adverse events other than intussusception may have occurred after RRV-TV and 2) the likely scope of gastrointestinal illnesses, of which the previously identified, highly specific intussusception cases may account for just a fraction.

SETTING AND PARTICIPANTS

Infants vaccinated with RRV-TV and other vaccines in the United States and for whom a report was submitted to VAERS during September 1, 1998, to December 31, 1999.

METHODOLOGY

To detect adverse events of interest other than intussusception, we used proportional morbidity analysis to compare the adverse event profile of VAERS reports among infants who received routine vaccines including RRV-TV (after excluding confirmed and suspected intussusception reports) with infants who received identical vaccine combinations but without RRV-TV. Next, to better capture all described diagnoses, signs, and symptoms associated with the suspected adverse events, a set of new codes was developed and assigned to each VAERS report. All 448 nonfatal RRV-TV-associated reports (including intussusception) were recoded manually from the clinical description on the VAERS report and categorized into clinical groups to better describe a spectrum of reported illnesses after the vaccine. Each report was assigned to one of the following hierarchical and mutually exclusive clinical groups: 1) diagnosed intussusception; 2) suspected intussusception; 3) illness consistent with either gastroenteritis or intussusception; 4) gastroenteritis; 5) other gastrointestinal diagnoses (ie, not consistent with intussusception or rotavirus-like gastroenteritis); and 6) nongastrointestinal diagnoses.

RESULTS

Even after excluding intussusception cases, a higher proportion of RRV-TV reports than non-RRV-TV reports included fever and various gastrointestinal symptoms, most notably bloody stool but also vomiting, diarrhea, abdominal pain, gastroenteritis, abnormal stool, and dehydration. Distribution of RRV-TV reports by clinical groups was as follows: diagnosed intussusception (109 [24%], suspected intussusception (36 [8%]), and illness consistent with gastroenteritis or intussusception (33 [7%]), gastroenteritis (101 [22%]), other gastrointestinal diagnoses (10 [2%]), and nongastrointestinal outcomes (159 [35%]). The median time interval between vaccination and illness onset decreased incrementally among the first 4 clinical groups: from 7 days for diagnosed intussusceptions to 3 days for gastroenteritis.

CONCLUSIONS

Intussusception and gastroenteritis were the most commonly reported outcomes; however, a substantial number of reports indicate signs and symptoms consistent with either illness, possibly suggestive of a spectrum of gastrointestinal illness(es) related to RRV-TV. Although VAERS data have recognized limitations such as underreporting (that may differ by vaccine) and are nearly always insufficient to prove causality between a vaccine and an adverse event, this safety profile of RRV-TV may aid better understanding of the pathophysiology of intussusception as well as development of future safer rotavirus vaccines.

Application of quantitative signal detection in the Dutch spontaneous reporting system for adverse drug reactions

The primary aim of spontaneous reporting systems (SRSs) is the timely detection of unknown adverse drug reactions (ADRs), or signal detection. Generally this is carried out by a systematic manual review of every report sent to an SRS. Statistical analysis of the data sets of an SRS, or quantitative signal detection, can provide additional information concerning a possible relationship between a drug and an ADR. We describe the role of quantitative signal detection and the way it is applied at the Netherlands Pharmacovigilance Centre Lareb. Results of the statistical analysis are implemented in the traditional case-by-case analysis. In addition, for data-mining purposes, a list of associations of ADRs and suspected drugs that are disproportionally present in the database is periodically generated. Finally, quantitative signal generation can be used to study more complex relationships, such as drug-drug interactions and syndromes. The results of quantitative signal detection should be considered as an additional source of information, complementary to the traditional analysis. Techniques for the detection of drug interactions and syndromes offer a new challenge for pharmacovigilance in the near future.

Quantitative methods in pharmacovigilance: focus on signal detection

Pharmacovigilance serves to detect previously unrecognised adverse events associated with the use of medicines. The simplest method for detecting signals of such events is crude inspection of lists of spontaneously reported drug-event combinations. Quantitative and automated numerator-based methods such as Bayesian data mining can supplement or supplant these methods. The theoretical basis and limitations of these methods should be understood by drug safety professionals, and automated methods should not be automatically accepted. Published evaluations of these techniques are mainly limited to large regulatory databases, and performance characteristics may differ in smaller safety databases of drug developers. Head-to-head comparisons of the major techniques have not been published. Regardless of previous statistical training, pharmacovigilance practitioners should understand how these methods work. The mathematical basis of these techniques should not obscure the numerous confounders and biases inherent in the data. This article seeks to make automated signal detection methods transparent to drug safety professionals of various backgrounds. This is accomplished by first providing a brief overview of the evolution of signal detection followed by a series of sections devoted to the methods with the greatest utilisation and evidentiary support: proportional reporting rations, the Bayesian Confidence Propagation Neural Network and empirical Bayes screening. Sophisticated yet intuitive explanations are provided for each method, supported by figures in which the underlying statistical concepts are explored. Finally the strengths, limitations, pitfalls and outstanding unresolved issues are discussed. Pharmacovigilance specialists should not be intimidated by the mathematics. Understanding the theoretical basis of these methods should enhance the effective assessment and possible implementation of these techniques by drug safety professionals.

Practical pharmacovigilance analysis strategies

PURPOSE

To compare two recently proposed Bayesian methods for quantitative pharmacovigilance with respect to assumptions and results, and to describe some practical strategies for their use.

METHODS

The two methods were expressed in common terms to simplify identifying similarities and differences, some extensions to both methods were provided, and the empirical Bayes method was applied to accumulated experience on a new antihypertensive drug to elucidate the pattern of adverse-event reporting. Both methods use the logarithm of the proportional risk ratio as the basic metric for association.

RESULTS

The two methods provide similar numerical results for frequently reported events, but not necessarily when few events are reported. Using a lower 5% quantile of the posterior distribution gives some assurance that potential signals are unlikely to be noise. The calculations indicated that most potential adverse event-drug associations that were well-recognized after 6 years of use could be identified within the first year, that most of the associations identified in the first year persisted over time. Other insights into the pattern of event reporting were also noted.

CONCLUSION

Both methods can provide useful early signals of potential drug-event associations that subsequently can be the focus of detailed evaluation by skilled clinicians and epidemiologists.

Ethics, data-dependent designs, and the strategy of clinical trials: time to start learning-as-we-go?

The seeds of modern clinical trials were unwittingly sown with the first use of randomization in a 1920s agricultural field experiment. The historical development of trials is briefly reviewed here, as are multifarious pressures and problems faced by those involved with clinical trials today. These challenges include recruitment difficulties, the emerging role of patient support groups, and legal threats over informed consent, to name three. Fundamentally, they reflect an overall shift towards patient-centred, individual ethics. I suggest many problems may be overcome by increased implementation of hitherto neglected, data-dependent designs for clinical trials. Over a dozen arguments against their use are countered, primarily through ethical considerations. Benefits and costs of refining clinical trials strategy are explored hypothetically under enhanced use of such 'learn-as-you-go' designs, in contrast to traditional, equal-allocation, fixed-sample-size and frequentist-based designs. These latter methods mirror crop field trials in which one cannot make scientific progress until after gathering objective data at harvest time. Some attempts to alleviate certain problems, such as Zelen randomization to boost recruitment, or over-reliance on 'large and simple trials' to detect moderate-sized treatment effects, are discussed and found inadequate. A proposal for wider discussion is made to assist the selective introduction of 'small and complex trials,' which could simultaneously expedite medical research, satisfy the concerns of regulators, statisticians, and doctors alike, and help address the growing demands of 21st-century patients.

Use of measures of disproportionality in pharmacovigilance: three Dutch examples

Spontaneous reporting systems for suspected adverse drug reactions (ADRs) remain a cornerstone of pharmacovigilance. In The Netherlands 'the Netherlands Pharmacovigilance Foundation Lareb' maintains such a system. A primary aim in pharmacovigilance is the timely detection of either new ADRs or a change of the frequency of ADRs that are already known to be associated with the drugs involved, i.e. signal detection. Adequate signal detection solely based on the human intellect (case by case analysis or qualitative signal detection) is becoming time consuming given the increasingly large number of data, as well as less effective, especially in more complex associations such as drug-drug interactions, syndromes and when various covariates are involved. In quantitative signal detection measures that express the extent in which combinations of drug(s) and clinical event(s) are disproportionately present in the database of reported suspected ADRs are used to reveal associations of interest. Although the rationale and the methodology of the various quantitative approaches differ, they all share the characteristic that they express to what extent the number of observed cases differs from the number of expected cases. In this paper three Dutch examples are described in which a measure of disproportionality is used in quantitative signal detection in pharmacovigilance: (i) the association between antidepressant drugs and the occurrence of non-puerpural lactation as an example of an association between a single drug and a single event; (ii) the onset or worsening of congestive heart failure associated with the combined use of nonsteroidal anti-inflammatory drugs and diuretics as an example of an association between two drugs and a single event (drug-drug interaction); and the (iii) (co)-occurrence of fever, urticaria and arthralgia and the use of terbinafine as an example of an association between a single drug and multiple events (syndrome). We conclude that the use of quantitative measures in addition to qualitative analysis is a step forward in signal detection in pharmacovigilance. More research is necessary into the performance of these approaches, especially its predictive value, its robustness as well as into further extensions of the methodology.

On the assessment of adverse drug reactions from spontaneous reporting systems: the influence of under-reporting on odds ratios

A well-known problem in spontaneous reporting systems (SRSs) for adverse drug reactions (ADRs) is under-reporting, that is, the problem that not all occurrences of ADRs are reported to the SRS. We look at the question of how to draw statistical conclusions from analyses of SRS data using reporting odds ratios. We will show that certain under-reporting problems play no role in assessing ADRs from SRSs: the results from the analyses turn out to be biased by some specific under-reporting problems, but not by others. SRS data can be particularly useful for the assessment of drug-drug interactions. If the assumption holds that there is an under-reporting problem for a first drug, and an under-reporting problem for a second drug, but that these two under-reporting problems do not influence each other, then reporting odds ratios estimated from SRSs are useful for signalling drug-drug interactions in the ADR-experiencing population. Similar results hold for covariate-drug interactions. We illustrate our results using two examples.

A comparison of measures of disproportionality for signal detection in spontaneous reporting systems for adverse drug reactions

PURPOSE

A continuous systematic review of all combinations of drugs and suspected adverse reactions (ADRs) reported to a spontaneous reporting system, is necessary to optimize signal detection. To focus attention of human reviewers, quantitative procedures can be used to sift data in different ways. In various centres, different measures are used to quantify the extent to which an ADR is reported disproportionally to a certain drug compared to the generality of the database. The objective of this study is to examine the level of concordance of the various estimates to the measure used by the WHO Collaborating Centre for International ADR monitoring, the information component (IC), when applied to the dataset of the Netherlands Pharmacovigilance Foundation Lareb.

METHODS

The Reporting Odds Ratio--1.96 standard errors (SE), proportional reporting ratio--1.96 SE, Yule's Q--1.96 SE, the Poisson probability and Chi-square test of all 17,330 combinations were compared with the IC minus 2 standard deviations. Additionally, the concordance of the various tests, in respect to the number of reports per combination, was examined.

RESULTS

In general, sensitivity was high in respect to the reference measure when a combination of point- and precision estimate was used. The concordance increased dramatically when the number of reports per combination increased.

CONCLUSION

This study shows that the different measures used are broadly comparable when four or more cases per combination have been collected.