Self-controlled designs in pharmacoepidemiology involving electronic healthcare databases: a systematic review

Use of the French National Health Data System (SNDS) in pharmacoepidemiology: A systematic review in its maturation phase

AIM OF THE STUDY

The French National Health Data System (SNDS) comprises healthcare data that cover 99% of the population (over 67 million individuals) in France. The aim of this study was to present an overview of published pharmacoepidemiological studies using the SNDS in its maturation phase.

METHODS

We conducted a systematic literature review of original research articles in the Pubmed and EMBASE databases from January 2012 until August 2018.

RESULTS

A total of 316 full-text articles were included, with an annual increase over the study period. Only 16 records were excluded after screening because they did not involve the SNDS but other French healthcare databases. The study design was clearly reported in only 66% of studies of which 57% were retrospective cohorts and 22% cross-sectional studies. The reported study objectives were drug utilization (65%), safety (22%) and effectiveness (9%). Almost all ATC groups were studied but the most frequent ones concerned the nervous system in 149 studies (49%), cardiovascular system drugs in 104 studies (34%) and anti-infectives for systemic use in 50 studies (16%).

CONCLUSION

The SNDS is of growing interest for studies on drug use and safety, which could be conducted more in specific populations, including children, pregnant women and the elderly, as these populations are often not included in clinical trials.

Triptan use in elderly over 65 years and the risk of hospitalization for serious vascular events

BACKGROUND

Several studies have focused on the use of triptan and the risk of acute vascular events but the existence of such association is still debated and has never been quantified in patients over 65 years. To assess whether triptan use among older is associated with an increased risk of hospitalization for acute vascular events.

METHODS

A propensity score-matched cohort study was designed using the French national health insurance database linked to hospital stays. Patients aged ≥ 65 years, newly treated by triptans between 2011 and 2014, were included… The primary event was hospitalization for an acute ischemic vascular event within de 90 days following triptan initiation. Association with triptan exposure was investigated through cox regression model, considering exposure at inclusion, and with exposure as a time-varying variable A case-crossover (CCO) and a self-controlled case series (SCCS) analyses were also conducted to address potential residual confounding.

RESULTS

The cohort included 24, 774 triptan users and 99 096 propensity matched controls (mean (SD) age: 71 years (5.9), 74% of women). Within 90 days after cohort entry, 163 events were observed in the triptan group, and 523 in the control group (0.66% vs. 0.53%, adjusted hazard ratio (aHR) exposed/not exposed 1.25 95%CI [1.05-1.49]; aHR time-varying 8.74 [5.21-14.66]). The association was significant (CCO) for all events (adjusted odds ratio (aOR1.63 [1.22-2.19]) with a more consistent association with cerebral events (aOR 2.14 [1.26-3.63]). The relative incidence (RI) for all events was 2.13 [1.76-2.58] in the SCCS, for cardiac (RI: 1.67 [1.23-2.27]) and for cerebral events (RI: 3.20, [2.30-4.45]).

CONCLUSION

The incidence of acute vascular events was low among triptan users. We found that triptan use among older may be associated with a low increased risk for acute vascular events, which may be more marked for cerebral events such as stroke, than for cardiac events.

The COVID-19 Vaccine Safety Research Center: a cornerstone for strengthening safety evidence for COVID-19 vaccination in the Republic of Korea

The COVID-19 Vaccine Safety Research Committee (CoVaSC) was established in November 2021 to address the growing need for independent, in-depth scientific evidence on adverse events (AEs) following coronavirus disease 2019 (COVID-19) vaccination. This initiative was requested by the Korea Disease Control and Prevention Agency and led by the National Academy of Medicine of Korea. In September 2022, the COVID-19 Vaccine Safety Research Center was established, strengthening CoVaSC's initiatives. The center has conducted various studies on the safety of COVID-19 vaccines. During CoVaSC's second research year, from September 29, 2022 to July 19, 2023, the center was restructured into 4 departments: Epidemiological Research, Clinical Research, Communication & Education, and International Cooperation & Policy Research. Its main activities include (1) managing CoVaSC and the COVID-19 Vaccine Safety Research Center, (2) surveying domestic and international trends in AE causality investigation, (3) assessing AEs following COVID-19 vaccination, (4) fostering international collaboration and policy research, and (5) organizing regular fora and training sessions for the public and clinicians. Causality assessments have been conducted for 27 diseases, and independent research has been conducted after organizing ad hoc committees comprising both epidemiologists and clinical experts on each AE of interest. The research process included protocol development, data analysis, interpretation of results, and causality assessment. These research outcomes have been shared transparently with the public and healthcare experts through various fora. The COVID-19 Vaccine Safety Research Center plans to continue strengthening and expanding its research activities to provide reliable, high-quality safety information to the public.

Comparison design and evaluation power in cohort and self-controlled case series designs for post-authorization vaccine safety studies

Background

Post-authorization safety studies (PASSs) of vaccines are important. PASSs enable the evaluation of association between vaccination and adverse events following immunization through common study designs. Clinical trials during vaccine development typically include a few thousand to 10,000 participants while a PASS might aim to detect a few adverse events per 100,000 vaccine recipients. While all available data may be utilized, prior consideration of power analyses are nonetheless crucial for interpretation in cases where statistically significant differences are not found.

Methods

This research primarily examined cohort study design and self-controlled case series (SCCS) design, estimating the power of a PASS under plausible conditions.

Results

Both the cohort study and SCCS designs necessitated large sample sizes or high event counts to guarantee adequate power. The SCCS design is particularly suited to evaluating rare adverse events. However, extremely rare events may not yield sufficient occurrences, thereby resulting in low power. Although the SCCS design can more efficiently control for time-invariant confounding in principle, it solely estimates relative measures. A cohort study design might be preferred if confounding can be adequately managed as it also estimates absolute measures. It may be an easy decision to use all the data at hand for either design. We found it necessary to estimate the sample size and number of events to be used in the study based on a priori information and anticipated results.

The utility of the self-controlled study design for pharmacoepidemiological studies without an active comparator medication using a medical information database: An application to assess the risk of varenicline on cardiovascular outcomes

PURPOSE

To illustrate the utility of the self-controlled study design for studies without an active comparator, we compared the results of a cohort design study with a non-user comparator with those of a self-controlled design study in evaluating the risk of varenicline on cardiovascular outcomes, using a Japanese medical claims database.

METHODS

The participating smokers were identified from health-screening results collected between May 2008 and April 2017. Using a non-user-comparator cohort study design, we estimated the hazard ratios (HRs) and 95% confidence intervals (CIs) of varenicline on initial hospitalization with cardiovascular outcomes using Cox's model adjusted for patients' sex, age, medical history, medication history, and health-screening results. Using a self-controlled study design, the within-subject HR was estimated using a stratified Cox's model adjusted for medical history, medication history, and health-screening results. The estimate from a recent meta-analysis was considered the gold standard (risk ratio: 1.03).

RESULTS

We identified 460 464 smokers (398 694 males [86.6%]; mean (standard deviation) age: 42.9 [10.8] years) in the database. Of these, 11 561 had been dispensed varenicline at least once, and 4511 had experienced cardiovascular outcomes. The estimate of the non-user-comparator cohort study design exceeded the gold standard (HR [95% CI]: 2.04 [1.22-3.42]), whereas that of the self-controlled study design was close to the gold standard (within-subject HR [95% CI]: 1.12 [0.27-4.70]).

CONCLUSIONS

The self-controlled study design is useful alternative to a non-user-comparator cohort design when evaluating the risk of medications relative to their non-use, based on a medical information database.

Association Between Exposure to Effervescent Paracetamol and Hospitalization for Acute Heart Failure: A Case-Crossover Study

We investigated whether effervescent paracetamol, as an important source of non-dietary sodium and fluid load, is associated with a transient increase in the risk of hospitalization for acute heart failure (AHF). We conducted a unidirectional case-crossover study using data from the 1/97^th representative sample from the French healthcare database. Subjects aged 18 years or more, hospitalized for AHF during the 2014-2016 period were included. Exposure to effervescent paracetamol was compared between a risk period (i.e. 15 days immediately prior to admission for AHF) and three earlier 15-day control periods, to test a possible trigger effect of effervescent paracetamol intake on AHF. Adjusted odds ratios (aOR) were estimated with a conditional logistic regression. We identified 4,301 patients hospitalized for AHF. We found that 5.7% of AHF subjects were exposed to effervescent paracetamol during the risk period, as compared with 4.1% during the control periods (aOR 1.56 [CI_95% : 1.27 - 1.90], p < 0.001). This association was also found in the subgroup of subjects with hypertension (aOR 1.45 [CI_95% : 1.13 - 1.87], p = 0.004, n = 2,648) and in the subgroup of subjects aged 83 years or more (aOR 1.70 [CI_95% : 1.28 - 2.24], p < 0.001, n = 2,238). A similar analysis, considering exposure to non-effervescent paracetamol, did not support the existence of an indication bias likely to explain the association observed for effervescent paracetamol. This study suggests an association between effervescent paracetamol and admission for AHF and should be confirmed with other complementary study designs. This article is protected by copyright. All rights reserved.

Self-controlled case series design in vaccine safety: a systematic review

BACKGROUND

: An increasing number of vaccine safety studies using the self-controlled case-series (SCCS) design have been conducted in the last decade. However, there has been no comprehensive evaluation of the methodology and reporting quality of these observational studies. The purpose of this paper is to document the methodological features of studies that focused on vaccine safety using the SCCS design, and to evaluate the reporting quality of these studies to suggest future improvements on appropriate design and transparent reporting.

METHODS

: Databases including Medline, Embase, Web of Science, Scopus and Chinese databases were searched from inception to May 31, 2021. All observational studies regarding vaccine safety using a SCCS design were selected. Information regarding methodological elements were extracted. In addition, reporting quality was assessed using the REporting of studies Conducted using Observational Routinely collected health Data statement for PharmacoEpidemiology (RECORD-PE).

RESULTS

: Of the 105 studies identified, administrative databases were the main data source for vaccination records and adverse events following immunization (AEFI). 28 articles (27%) used multiple designs to verify the association, and the results obtained with the SCCS design were robust. The top three AEFI studied were intussusception, Guillain-Barré syndrome, and convulsions. Only 21 studies (20%) reported the approach for case validation by chart review. The healthy vaccinee effect was considered by 51studies (49%), with 16 of them (31%) using extended SCCS models to alleviate this effect. Overall, the reporting quality of included studies could be improved.

CONCLUSIONS

: This study systematically reviewed the methodology of studies regarding vaccine safety using a SCCS design and critically assessed their respective reporting quality. Case validation, the validity of assumptions for standard SCCS, and quality of reporting should be given more importance in future research projects.

Patient-Reported Nausea and Fatigue Related to Methotrexate: A Prospective, Self-Controlled Study in the ArthritisPower® Registry

Introduction

The magnitude and frequency of temporally related methotrexate (MTX)-associated side effects in rheumatoid arthritis (RA) or psoriatic arthritis (PsA) patients are difficult to quantify using traditional research methods. As proof of concept designed in part to implement digital data collection for remote patient monitoring, we conducted a study implementing self-controlled case series analytic methods to understand MTX-related symptoms in RA or PsA.

Methods

In study phase 1, adults with RA or PsA from the ArthritisPower^® Registry (past or current oral MTX users) participated in a cross-sectional survey. In phase 2, current MTX users participated in a longitudinal study and completed the Patient-Reported Outcomes Measurement Information System (PROMIS^®) 1-day nausea/vomiting and fatigue measure. Within-person change in PROMIS scores between risk (6–36 h post-dose) and control (96–144 h post-dose) windows were compared using mixed models.

Results

The baseline survey was completed by 671 participants (mean age: 54 years, 88% female, 92% white, 79% with RA). Among current MTX users (353/671 [53%]), most reported MTX-associated side effects (216/353 [61%]), most frequently fatigue (161/353 [46%]). Among phase 2 participants with (n = 39) and without (n = 84) baseline nausea, mean increase in PROMIS nausea was 5.1 units (P < 0.0001) and 0.7 units (P = 0.135), respectively; among those with (n = 51) and without (n = 72) baseline fatigue, mean increase in PROMIS fatigue was 3.9 units (P = 0.0003) and 0.4 units (P = 0.554), respectively.

Conclusions

Digital remote patient monitoring presents an opportunity to detect and address medication tolerability in real time. Using a novel study design to control for between-person confounding, the magnitude of nausea and fatigue experienced by participants with RA and PsA temporally related to weekly MTX use was substantial.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40744-021-00398-6.

Using Population-Based Structures to Actively Monitor AEFIs during a Mass Immunization Campaign-A Case of Measles-Rubella and Polio Vaccines

Active vaccine pharmacovigilance complements the standard passive or spontaneous surveillance system, which suffers from low reporting rates. This study aimed at utilizing population-based structures to report and profile adverse events following immunization (AEFI) with the measles and rubella vaccine (MR), or MR in combination with the bivalent oral polio vaccine (bOPV 1&3) (MR & bOPV), during mass vaccination in Uganda. Caretakers of children at home (less than 5 years) and schoolgoing children were followed up on and encouraged to report any AEFIs on day one, 2-3 days, 10 days, and 14 days after vaccination at school by their teachers and at-home, community-based village health teams. Out of 9798 children followed up on, 382 (3.9%) reported at least one AEFI, and in total, 517 AEFIs were reported. For MR, high temperature (21%), general feeling of weakness (19.3%), and headache (13%) were the most reported AEFIs, though there were variations on the days when they were reported. For the combination dose of MR & bOPV, high temperature (44%), rash (17%), general feeling of weakness (13%), and diarrhoea (8%) were the most common adverse events following immunization reported by caretakers. All 382 children cleared the AEFIs within 2 days, with 343 (90%) children reporting mild or moderate AEFIs and only 39 (10%) reporting severe AEFIs. The reported AEFIs are known and are mentioned in the vaccine leaflets with similar severity classification. Rates of AEFIs differed with the number of days after receiving the immunization. Conclusion: Active surveillance for AEFIs provides additional important information to national vaccine regulatory bodies. It reassures the public that vaccines are safe and that their safety is being taken seriously in Uganda, which would improve vaccine acceptability and confidence in the health system. Piggybacking on existing structures such as village health team members (for children at home) and teachers (for schoolgoing children) facilitates reaching vaccine recipients and increases reporting rates. Therefore, studies using active reporting of AEFIs should be conducted at regular intervals to report the overall incidence of AEs and to monitor trends and changes.

Association Between Third-Generation Fluoroquinolones and Achilles Tendon Rupture: A Self-Controlled Case Series Analysis

PURPOSE

We investigated whether use of third-generation fluoroquinolones is associated with occurrence of Achilles tendon rupture using a case series analysis in which patients served as their own control.

METHODS

We used administrative claims data to identify residents in a single Japanese prefecture who were enrolled in National Health Insurance and Elderly Health Insurance from April 2012 to March 2017 and experienced Achilles tendon rupture after receiving an antibiotic prescription. Antibiotics were categorized into 3 groups: first- and second-generation fluoroquinolones, third-generation fluoroquinolones, and nonfluoroquinolones. We used a conditional Poisson regression model to estimate the incidence rate ratio (IRR) of Achilles tendon rupture during the antibiotic exposure period relative to the nonexposure period for each patient. An exposure period was defined as 30 days from start of the prescription.

RESULTS

Analyses were based on 504 patients with Achilles tendon rupture who had received antibiotic prescriptions. Risk of rupture was not significantly elevated during exposure to third-generation fluoroquinolones (IRR = 1.05; 95% CI, 0.33-3.37) and nonfluoroquinolones (IRR = 1.08; 95% CI, 0.80-1.47). In contrast, risk was significantly elevated during exposure to first- and second-generation fluoroquinolones (IRR = 2.94; 95% CI, 1.90-4.54). Findings were similar across subgroups stratified by sex and by recent corticosteroid use.

CONCLUSIONS

Our analysis showed that third-generation fluoroquinolone use was not associated with an increased risk of Achilles tendon rupture. These antibiotics may be a safer option for patients in whom this risk is elevated, such as athletes.

Using the Case-Crossover Design to Assess Short-Term Risks of Bleeding and Arterial Thromboembolism After Switching Between Oral Anticoagulants in a Population-Based Cohort of Patients With Atrial Fibrillation

Using nationwide Danish registries, we conducted a population-based case-crossover study evaluating the association between switching from a vitamin K antagonist (VKA) to a direct oral anticoagulant (DOAC), and vice versa, and 30-day risks of bleeding and arterial thromboembolism in patients with atrial fibrillation (AF). The case-crossover population was identified among oral anticoagulant users during 2011-2018 (n = 123,217) as patients with AF with 1) a case-defining outcome and 2) an anticoagulant switch during the 180 days preceding the outcome. Odds ratios were estimated using conditional logistic regression by comparing the occurrence of switching during the 30-day window immediately preceding the outcome to that in reference windows in the same individual 60-180 days before the outcome. The case-crossover populations for switching from VKA to DOAC and DOAC to VKA comprised 1,382 and 287 case patients, respectively. Switching from VKA to DOAC, but not from DOAC to VKA, was associated with an increased short-term risk of bleeding (odds ratio = 1.42; 95% confidence intervals: 1.13, 1.79, and 1.06; and 0.64, 1.75, respectively) and ischemic stroke (odds ratio = 1.74; 95% confidence intervals: 1.21, 2.51, and 0.92; and 0.46, 1.83, respectively). Our findings suggest that switching from VKA to DOAC is an intermittent risk factor of bleeding and ischemic stroke in patients with AF.

ConvSCCS: convolutional self-controlled case series model for lagged adverse event detection

With the increased availability of large electronic health records databases comes the chance of enhancing health risks screening. Most post-marketing detection of adverse drug reaction (ADR) relies on physicians' spontaneous reports, leading to under-reporting. To take up this challenge, we develop a scalable model to estimate the effect of multiple longitudinal features (drug exposures) on a rare longitudinal outcome. Our procedure is based on a conditional Poisson regression model also known as self-controlled case series (SCCS). To overcome the need of precise risk periods specification, we model the intensity of outcomes using a convolution between exposures and step functions, which are penalized using a combination of group-Lasso and total-variation. Up to our knowledge, this is the first SCCS model with flexible intensity able to handle multiple longitudinal features in a single model. We show that this approach improves the state-of-the-art in terms of mean absolute error and computation time for the estimation of relative risks on simulated data. We apply this method on an ADR detection problem, using a cohort of diabetic patients extracted from the large French national health insurance database (SNIIRAM), a claims database containing medical reimbursements of more than 53 million people. This work has been done in the context of a research partnership between Ecole Polytechnique and CNAMTS (in charge of SNIIRAM).

Association Between Oral Corticosteroid Bursts and Severe Adverse Events : A Nationwide Population-Based Cohort Study

BACKGROUND

Long-term use of oral corticosteroids has known adverse effects, but the risk from brief oral steroid bursts (≤14 days) is largely unknown.

OBJECTIVE

To examine the associations between steroid bursts and severe adverse events, specifically gastrointestinal (GI) bleeding, sepsis, and heart failure.

DESIGN

Self-controlled case series.

SETTING

Entire National Health Insurance Research Database of medical claims records in Taiwan.

PARTICIPANTS

Adults aged 20 to 64 years with continuous enrollment in the National Health Insurance program from 1 January 2013 to 31 December 2015.

MEASUREMENTS

Incidence rates of severe adverse events in steroid burst users and non-steroid users, as well as incidence rate ratios (IRRs) for severe adverse events within 5 to 30 and 31 to 90 days after initiation of steroid therapy.

RESULTS

Of 15 859 129 adult participants, 2 623 327 who received a single steroid burst were included. The most common indications were skin disorders and respiratory tract infections. The incidence rates per 1000 person-years in steroid bursts were 27.1 (95% CI, 26.7 to 27.5) for GI bleeding, 1.5 (CI, 1.4 to 1.6) for sepsis, and 1.3 (CI, 1.2 to 1.4) for heart failure. Rates of GI bleeding (IRR, 1.80 [CI, 1.75 to 1.84]), sepsis (IRR, 1.99 [CI, 1.70 to 2.32]), and heart failure (IRR, 2.37 [CI, 2.13 to 2.63]) significantly increased within 5 to 30 days after steroid therapy initiation and attenuated during the subsequent 31 to 90 days.

LIMITATION

Persons younger than 20 years or older than 64 years were not included.

CONCLUSION

Oral corticosteroid bursts are frequently prescribed in the general adult population in Taiwan. The highest rates of GI bleeding, sepsis, and heart failure occurred within the first month after initiation of steroid therapy.

PRIMARY FUNDING SOURCE

National Health Research Institutes, Ministry of Science and Technology of Taiwan, Chang Gung Medical Foundation, and Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Antipsychotic medication exposure, clozapine, and pneumonia: results from a self-controlled study

OBJECTIVE

By using a self-controlled design, we investigated whether antipsychotic medication exposure was associated with increased pneumonia risk and whether patients receiving clozapine were more likely to develop pneumonia than patients receiving other antipsychotic medications.

METHODS

Through nationwide health registers, we identified all out-patients with schizophrenia initiating antipsychotic treatment. First, we estimated whether antipsychotic-naïve patients with schizophrenia increased their risk of pneumonia after initiation of either a first- or second-generation antipsychotic medication using a one-year mirror-image model. Afterward, similar analyses were made for individual second-generation antipsychotics. Lastly, the rate of pneumonia for patients initiated on clozapine was compared to patients commenced on other second-generation antipsychotics.

RESULTS

In total, 8355 antipsychotic-naïve patients with schizophrenia were initiated on a first-generation antipsychotic medication; 0.95% of the patients had developed pneumonia before exposure, compared to 0.68% after exposure (P = 0.057). Similar findings were made for the 8001 antipsychotic-naïve patients with schizophrenia initiated on second-generation antipsychotic medications, with 0.56% developing pneumonia before exposure compared to 0.55% after exposure (P = 1.00). Second-generation antipsychotic medications did not increase the pneumonia risk, except for risperidone (increased by 0.32%; P = 0.007) and clozapine, which gave the largest absolute increase in pneumonia risk although not significant (increased by 0.64%; P = 0.10). The rate of pneumonia was higher after initiation of clozapine than for other second-generation antipsychotic medications.

CONCLUSION

Most antipsychotic medications were not found to increase the risk of pneumonia. Clozapine exposure might be associated with increased risk of developing pneumonia.

Bias in case-crossover studies of medications due to persistent use: A simulation study

PURPOSE

The case-crossover design is increasingly used to evaluate the effects of chronic medications; however, as traditionally implemented in pharmacoepidemiology, with referent period preceding the outcome, it may lead to bias in the presence of persistent exposures. We aimed to evaluate the extent and magnitude of bias in case-crossover analyses of chronic and persistent exposures, using simulations.

METHODS

We simulated cohorts with either 30-day, 180-day, or 2-year exposure duration; and with varying degrees of persistence (10%, 30%, 50%, 70%, or 90% of patients not stopping exposure). We evaluated all scenarios under the null and the scenario with 30% persistence under varying exposure effects (odds ratios of 0.25 to 4.0). Cohorts were analyzed using conditional logistic regression that compared the odds of exposure on the outcome day to the odds of exposure on a referent day 30 days prior to the outcome. We further implemented the case-time-control design to evaluate its ability to adjust for bias from persistence.

RESULTS

Case-crossover analyses produced unbiased estimates across all scenarios without persistent users, regardless of exposure duration. In scenarios where some patients persisted on treatment, case-crossover analyses resulted in upward bias, which increased with increasing proportion of persistent users, but did not vary substantially in relation to the magnitude of the true effect. Case-time-control analyses removed bias in all scenarios.

CONCLUSIONS

Investigators should be aware of bias due to treatment persistence in unidirectional case-crossover analyses of chronic medications, which can be remedied with a control group of similarly persistent noncases.

Risk of acute kidney injury following community prescription of antibiotics: self-controlled case series

BACKGROUND

Development of acute kidney injury (AKI) following the use of antibiotics such as sulphonamides, trimethoprim and aminoglycosides is a frequently described phenomenon. More recently, an association between fluoroquinolone use and AKI has been suggested. The aim of this study was to evaluate the risk of AKI as an unintended consequence of commonly prescribed antibiotics in a large community cohort using a method that fully adjusts for underlying patient characteristics, including potential unmeasured confounders.

METHODS

A self-controlled case study was conducted and included all individuals aged 18 years and over in the Tayside region of Scotland who had a serum creatinine measured between 1 January 2004 and 31 December 2012. AKI episodes were defined using the Kidney Disease: Improving Global Outcomes definition. Data on oral community-prescribed antibiotics (penicillins, cephalosporins, fluoroquinolones, sulphonamides and trimethoprim, macrolides and nitrofurantoin) were collected for all individuals. Incidence rate ratios (IRRs) for AKI associated with antibiotic exposure versus time periods without antibiotic exposure were calculated.

RESULTS

Combined use of sulphonamides, trimethoprim and nitrofurantoin rose by 47% and incidence of community-acquired AKI rose by 16% between 2008 and 2012. During the study period 12 777 individuals developed 14 900 episodes of AKI in the community, of which 68% was AKI Stage 1, 16% Stage 2 and 16% Stage 3. The IRR of AKI during any antibiotic use was 1.16 [95% confidence interval (CI) 1.10-1.23], and this was highest during sulphonamides or trimethoprim use; IRR 3.07 (95% CI 2.81-3.35). Fluoroquinolone and nitrofurantoin use was not associated with a significantly increased rate of AKI; IRR 1.13 (95% CI 0.94-1.35) and 1.16 (95% CI 0.91-1.50), respectively.

CONCLUSIONS

Incidence of AKI rose by 16% between 2008 and 2012. In the same period the use of sulphonamides, trimethoprim and nitrofurantoin increased by 47%. A significant increased risk of AKI was seen with the use of sulphonamides and trimethoprim, but not with fluoroquinolones or nitrofurantoin.

Comparison of Different Case-Crossover Variants in Handling Exposure-Time Trend or Persistent-User Bias: Using Dipeptidyl Peptidase-4 Inhibitors and the Risk of Heart Failure as an Example

OBJECTIVES

Inappropriate use of the case-crossover design, which is efficient for examining associations between brief exposure and abrupt outcomes, in evaluating the effects of medications in the presence of exposure-time trends or persistent drug use may generate spurious associations. We compared different approaches to adjusting for these sources of bias by examining the risk of heart failure hospitalization (HFH) associated with dipeptidyl peptidase-4 (DPP-4) inhibitors. Overall, existing evidence does not suggest a higher risk of HFH associated with DPP-4 inhibitors; however, case-crossover analyses of these medications may be susceptible to bias.

METHODS

We conducted case-crossover; age, sex, risk-set (ASR) matched case-time-control; disease risk score (DRS)-matched case-time-control; and case-case-time-control analyses to assess the association between DPP-4 inhibitors and HFH among patients with diabetes mellitus (DM) in a population-based Taiwanese database. We also examined metformin and sulfonylureas, both with assumed null associations.

RESULTS

Among 362 022 DM patients, 4105 (case-crossover), 4103 (ASR-matched case-time-control), 3957 (DRS-matched case-time-control), and 2812 (case-case-time-control) HFH cases were identified. The OR for DPP-4 inhibitors and HFH was elevated in the case-crossover analysis (1.52; 95% confidence interval [95% CI] 0.95-2.42). The ASR-matched case-time control, DRS-matched case-time-control, and case-case-time control analyses yielded near-null associations (0.90 [95% CI 0.45-1.83], 0.96 [95% CI 0.46-2.02], and 0.92 [95% CI 0.39-2.21], respectively). Null effects were observed for metformin across designs and for sulfonylureas in the case-case-time control analysis.

CONCLUSIONS

Our case-crossover analysis suggested DPP-4 inhibitors may be associated with HFH; however, each method for adjusting for exposure-time and persistent user bias attenuated the findings. The case-case-time-control analysis had the least precision.

A plea to stop using the case-control design in retrospective database studies

The case‐control design is widely used in retrospective database studies, often leading to spectacular findings. However, results of these studies often cannot be replicated, and the advantage of this design over others is questionable. To demonstrate the shortcomings of applications of this design, we replicate two published case‐control studies. The first investigates isotretinoin and ulcerative colitis using a simple case‐control design. The second focuses on dipeptidyl peptidase‐4 inhibitors and acute pancreatitis, using a nested case‐control design. We include large sets of negative control exposures (where the true odds ratio is believed to be 1) in both studies. Both replication studies produce effect size estimates consistent with the original studies, but also generate estimates for the negative control exposures showing substantial residual bias. In contrast, applying a self‐controlled design to answer the same questions using the same data reveals far less bias. Although the case‐control design in general is not at fault, its application in retrospective database studies, where all exposure and covariate data for the entire cohort are available, is unnecessary, as other alternatives such as cohort and self‐controlled designs are available. Moreover, by focusing on cases and controls it opens the door to inappropriate comparisons between exposure groups, leading to confounding for which the design has few options to adjust for. We argue that this design should no longer be used in these types of data. At the very least, negative control exposures should be used to prove that the concerns raised here do not apply.

Antidepressant use during pregnancy and risk of congenital heart defects: A case-time-control study

PURPOSE

We estimated the association between maternal antidepressant (AD) use in early pregnancy and risk of congenital heart defects.

METHODS

We applied a case-time-control design with the aim of controlling for confounding from time-invariant factors and compared the results of the design to results from a cohort design in a population of 792 685 singletons born alive in Denmark during 1995-2008. In the case-time-control design, we identified children diagnosed with a congenital heart defect in the first 5 years of life (cases) and compared maternal AD use in the risk period (the first 3 months of pregnancy) and the reference period (gestational months 5-7). A nondiseased control group was included to adjust for time trends of exposure. In the cohort design, we identified children whose mothers redeemed at least one AD prescription in the first 3 months of pregnancy (the exposed) and two other groups including the unexposed children with maternal AD prescriptions in the 12 months before pregnancy. We applied conditional logistic regression and logistic regression to compute odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The case-time-control OR for any congenital heart defect was 1.03 (95% CI, 0.61-1.73), which was similar to the OR (1.09, 95% CI, 0.88-1.35) from the cohort design when we compared the exposed children with the unexposed children with maternal AD use before pregnancy.

CONCLUSIONS

The case-time-control design provided results similar to the cohort design when the cohort design had a better confounder control strategy. We discussed the strengths and drawbacks of case-time-control design.

Analysis of Observational Self-matched Data to Examine Acute Triggers of Outcome Events with Abrupt Onset

Several self-matched approaches have been proposed, including case-crossover, case-time control, fixed-effects case-time control, and self-controlled case series. Rather than comparing treatment effects between different individuals, studies use these approaches to evaluate the acute effects of transient exposures, often called “triggers,” by comparing outcome risk among the same individual at different times. This eliminates confounding by between-person characteristics that remain stable over time, allowing for valid analyses even in situations where information on some health behaviors is not available, such as long-term smoking history. However, to attain valid results, differences in the probability of exposure and outcome that change over time must be addressed in the design and analysis of the study. In this article, we describe the setting, assumptions and analytic options for conducting studies using self-matched data. Approaches that involve matching or a group of noncases to address time-varying confounding may have less statistical flexibility but they are powerful tools that overcome the need to assume a particular form of any time trends in potential confounders. If data are available for all of the person–time under study, there is a gain in statistical efficiency and the ability to address time-varying confounding using flexible regression models, under the strong assumption of no mis-specification of the model.

Intravitreal bevacizumab treatment for neovascular age-related macular degeneration and thromboembolic events

BACKGROUND

Systemic complications of intravitreal anti-vascular endothelial growth factor agents are relatively uncommon but highly significant.

OBJECTIVES

Primary objective: To assess the risk for thromboembolic events following intravitreal bevacizumab injection in neovascular age-related macular degeneration patients by a large population-based study. Secondary objective: To analyze the association between injection frequency and the risk for thromboembolic events, the time interval between the injection and the thromboembolic events, and the influence of chronic diseases on complications rate.

DESIGN

A retrospective cohort study.

METHODS

Consecutive neovascular age-related macular degeneration patients receiving intravitreal bevacizumab at Soroka University Medical Center from December 2005 to December 2013 were included. Thromboembolic events analyzed included acute coronary syndrome, acute myocardial infarction, stroke, deep vein thrombosis, and pulmonary embolism. The thromboembolic event rate was compared 2 years prior and 2 years after the initial intravitreal bevacizumab injection.

RESULTS

A total of 2102 patients were included. Acute coronary syndrome and stroke rate were higher 2 years after intravitreal bevacizumab (p = 0.03 and p = 0.01, respectively). No statistical significant difference was found for the rest of thromboembolic events. Patients older than 80 years and patients receiving less than six intravitreal bevacizumab injections were more likely to experience stroke. Patients with known cardiovascular risk factors before starting injections did not develop significant more thromboembolic events.

CONCLUSION

In our study population, patients treated with intravitreal bevacizumab were significantly more likely to experience stroke during 2 years after first injection.

Self-controlled case series studies: Just how rare does a rare non-recurrent outcome need to be?

The self-controlled case series method assumes that adverse outcomes arise according to a non-homogeneous Poisson process. This implies that it is applicable to independent recurrent outcomes. However, the self-controlled case series method may also be applied to unique, non-recurrent outcomes or first outcomes only, in the limit where these become rare. We investigate this rare outcome assumption when the self-controlled case series method is applied to non-recurrent outcomes. We study this requirement analytically and by simulation, and quantify what is meant by 'rare' in this context. In simulations we also apply the self-controlled risk interval design, a special case of the self-controlled case series design. To illustrate, we extract data on the incidence rate of some recurrent and non-recurrent outcomes within a defined study population to check whether outcomes are sufficiently rare for the rare outcome assumption to hold when applying the self-controlled case series method to first or unique outcomes. The main findings are that the relative bias should be no more than 5% when the cumulative incidence over total time observed is less than 0.1 per individual. Inclusion of age (or calendar time) effects will further reduce bias. Designs that begin observation with exposure maximise bias, whereas little or no bias will be apparent when there is no time trend in the distribution of exposures, or when exposure is central within time observed.

Assessment of Medication Safety Using Only Dispensing Data

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of the published studies that have been used to generate evidence on the safety of medicine use when only medication dispensing data are available.

RECENT FINDINGS

Medication dispensing databases are increasingly available for research on large populations, particularly in countries that provide universal coverage for medicines. These data are often used for drug utilisation studies to identify inappropriate medicine use at the population level that may be associated with known safety issues. Lack of coded diagnoses, to identify outcomes, and lack of data on confounders can limit use of these data in practice for medication safety assessment. To overcome these issues, studies have exploited the fact that symptoms of adverse effects of medications can be treated with other medications, for example antidepressants to treat depression or oxybutynin to treat urinary incontinence. The challenge of unmeasured confounding has been addressed by implementing self-controlled study designs that use within-person comparisons and provide inherent control for confounding. Prescription sequence symmetry analysis (SSA) is a within-person study design that has been demonstrated as a useful tool for safety signal generation in dispensing data.

SUMMARY

Using medicine initiation as a proxy for the development of adverse events can help to generate evidence of the safety of medicines when only medication dispensing data are available. Careful consideration, however, should be given to the sensitivity and specificity of the proxy medicine for the adverse event and potential for time-varying confounding due to trends in medicine utilisation. Data-mining approaches using dispensing data have the potential to improve safety assessments; however, the challenge of unmeasured confounding with these methods remains to be investigated.

Measurement Error and Misclassification in Electronic Medical Records: Methods to Mitigate Bias

PURPOSE OF REVIEW

We sought to: 1) examine common sources of measurement error in research using data from electronic medical records (EMR), 2) discuss methods to assess the extent and type of measurement error, and 3) describe recent developments in methods to address this source of bias.

RECENT FINDINGS

We identified eight sources of measurement error frequently encountered in EMR studies, the most prominent being that EMR data usually reflect only the health services and medications delivered within the specific health facility/system contributing to the EMR data. Methods for assessing measurement error in EMR data usually require gold standard or validation data, which may be possible using data linkage. Recent methodological developments to address the impact of measurement error in EMR analyses were particularly rich in the multiple imputation literature.

SUMMARY

Presently, sources of measurement error impacting EMR studies are still being elucidated, as are methods for assessing and addressing them. Given the magnitude of measurement error that has been reported, investigators are urged to carefully evaluate and rigorously address this potential source of bias in studies based in EMR data.

A comparison of estimators from self-controlled case series, case-crossover design, and sequence symmetry analysis for pharmacoepidemiological studies

Background

Despite the frequent use of self-controlled methods in pharmacoepidemiological studies, the factors that may bias the estimates from these methods have not been adequately compared in real-world settings. Here, we comparatively examined the impact of a time-varying confounder and its interactions with time-invariant confounders, time trends in exposures and events, restrictions, and misspecification of risk period durations on the estimators from three self-controlled methods. This study analyzed self-controlled case series (SCCS), case-crossover (CCO) design, and sequence symmetry analysis (SSA) using simulated and actual electronic medical records datasets.

Methods

We evaluated the performance of the three self-controlled methods in simulated cohorts for the following scenarios: 1) time-invariant confounding with interactions between the confounders, 2) time-invariant and time-varying confounding without interactions, 3) time-invariant and time-varying confounding with interactions among the confounders, 4) time trends in exposures and events, 5) restricted follow-up time based on event occurrence, and 6) patient restriction based on event history. The sensitivity of the estimators to misspecified risk period durations was also evaluated. As a case study, we applied these methods to evaluate the risk of macrolides on liver injury using electronic medical records.

Results

In the simulation analysis, time-varying confounding produced bias in the SCCS and CCO design estimates, which aggravated in the presence of interactions between the time-invariant and time-varying confounders. The SCCS estimates were biased by time trends in both exposures and events. Erroneously short risk periods introduced bias to the CCO design estimate, whereas erroneously long risk periods introduced bias to the estimates of all three methods. Restricting the follow-up time led to severe bias in the SSA estimates. The SCCS estimates were sensitive to patient restriction. The case study showed that although macrolide use was significantly associated with increased liver injury occurrence in all methods, the value of the estimates varied.

Conclusions

The estimations of the three self-controlled methods depended on various underlying assumptions, and the violation of these assumptions may cause non-negligible bias in the resulting estimates. Pharmacoepidemiologists should select the appropriate self-controlled method based on how well the relevant key assumptions are satisfied with respect to the available data.

Electronic supplementary material

The online version of this article (10.1186/s12874-017-0457-7) contains supplementary material, which is available to authorized users.

Development and application of two semi-automated tools for targeted medical product surveillance in a distributed data network

PURPOSE OF REVIEW

An important component of the Food and Drug Administration's Sentinel Initiative is the active post-market risk identification and analysis (ARIA) system, which utilizes semi-automated, parameterized computer programs to implement propensity-score adjusted and self-controlled risk interval designs to conduct targeted surveillance of medical products in the Sentinel Distributed Database. In this manuscript, we review literature relevant to the development of these programs and describe their application within the Sentinel Initiative.

RECENT FINDINGS

These quality-checked and publicly available tools have been successfully used to conduct rapid, replicable, and targeted safety analyses of several medical products. In addition to speed and reproducibility, use of semi-automated tools allows investigators to focus on decisions regarding key methodological parameters. We also identified challenges associated with the use of these methods in distributed and prospective datasets like the Sentinel Distributed Database, namely uncertainty regarding the optimal approach to estimating propensity scores in dynamic data among data partners of heterogeneous size.

SUMMARY

Future research should focus on the methodological challenges raised by these applications as well as developing new modular programs for targeted surveillance of medical products.