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Background: Case-crossover studies have been widely used in various fields including pharmacoepidemiology. Vines and Farrington indicated in 2001 that when within-subject exposure dependency exists, conditional logistic regression can be biased. However, this bias has not been well studied., Methods: We have extended findings by Vines and Farrington to develop a weighting method for the case-crossover study which removes bias from within-subject exposure dependency. Our method calculates the exposure probability at the case period in the case-crossover study which is used to weight the likelihood formulae presented by Greenland in 1999. We simulated data for the population with a disease where most patients receive a cyclic treatment pattern with within-subject exposure dependency but no time trends while some patients stop and start treatment. Finally, the method was applied to real-world data from Japan to study the association between celecoxib and peripheral edema and to study the association between selective serotonin reuptake inhibitor (SSRI) and hip fracture in Australia., Results: When the simulated rate ratio of the outcome was 4.0 in a case-crossover study with no time-varying confounder, the proposed weighting method and the Mantel-Haenszel odds ratio reproduced the true rate ratio. When a time-varying confounder existed, the Mantel-Haenszel method was biased but the weighting method was not. When more than one control period was used, standard conditional logistic regression was biased either with or without time-varying confounding and the bias increased (up to 8.7) when the study period was extended. In real-world analysis with a binary exposure variable in Japan and Australia, the point estimate of the odds ratio (around 2.5 for the association between celecoxib and peripheral edema and around 1.6 between SSRI and hip fracture) by our weighting method was equal to the Mantel-Haenszel odds ratio and stable compared with standard conditional logistic regression., Conclusion: Case-crossover studies may be biased from within-subject exposure dependency, even without exposure time trends. This bias can be identified by comparing the odds ratio by the Mantel-Haenszel method and that by standard conditional logistic regression. We recommend using our proposed method which removes bias from within-subject exposure dependency and can account for time-varying confounders., (© 2021. The Author(s).)

Introduction: A postmarketing study without a comparator group has been recognized as a problem as it provides no measure of association. Nevertheless, the design is sometimes used in company postmarketing studies particularly when the study involves the primary data collection. In this report, the "Symmetry Analysis Cohort Design" without a comparator group but with a control period is proposed., Methods and Results: In the proposed design, the rate ratio is estimated using the method of prescription sequence symmetry analysis with slight modification so that the rate ratio can be estimated using data on subjects who have started the drug during the study period but no data on other subjects., Discussion: The proposed design has an advantage that it can provide the measure of association. Another advantage common to all self-controlled methods is that the effect of the measured and unmeasured confounders is automatically canceled out when the effect is stable over the study period. Compared with the standard design with a comparator group, the proposed design also has weaknesses. For example, adjustment of confounding by the indication may be difficult when the indication is an acute condition. In addition, the rate ratio is not valid when the probability of the prescription of the drug is dependent on the occurrence of the outcome in the unexposed (pre-dose) period. The design may be used to evaluate the need for further studies although its real usefulness is to be determined in the future., (Copyright © 2015 John Wiley & Sons, Ltd.)

Purpose: To undertake a multi-country study to investigate the risk of acute hyperglycaemia with antipsychotic use., Methods: Using a distributed network model with a common minimal data set, we performed a prescription sequence symmetry analysis (PSSA) to investigate the risk of acute hyperglycaemia associated with antipsychotic initiation. Incident insulin prescriptions were used as a proxy indicator of acute hyperglycaemia. Participating countries and population datasets included Australia (300,000 persons), Japan I (300,000 persons), Japan II (200,000 persons), Korea (53 million persons) Taiwan (1 million persons), Sweden (9 million persons), USA-Public (87 million persons) and USA-Private (47 million persons)., Results: Olanzapine showed a trend towards increased risk in most databases, with a significant association observed in the USA-Public database (Adjusted sequence ratio (ASR) = 1.14; 95% Confidence Interval (CI) 1.10-1.17) and Sweden (ASR = 1.53; 95% CI 1.13-2.06). Null or negative associations were observed for haloperidol, quetiapine and risperidone., Conclusion: Acute hyperglycaemia appears to be associated with olanzapine use, however, this effect was only observed in two large databases. Despite different patterns of utilization of both antipsychotics and insulin, PSSA analysis results for individual antipsychotic medicines were qualitatively similar across most countries. PSSA, used in conjunction with existing methods, may provide a simple and timely method further supporting multi-national drug safety monitoring., (Copyright © 2013 John Wiley & Sons, Ltd.)

Purpose: Five data mining methodologies for detecting a possible signal from spontaneous reports on adverse drug reactions (ADRs) were compared., Methods: The five methodologies, the Bayesian method using the Gamma Poissson Shrinker (GPS), the method employed in the UK Medicines Control Agency (MCA), the Bayesian Confidence Propagation Neural Network (BCPNN), the method using the 95% confidence interval (CI) for the reporting odds ratio (RORCI) and that using the 95% CI of the proportional reporting ratio (PRRCI) were compared using Japanese data obtained between 1998 and 2000., Results: There were all in all 38,731 drug-ADR combinations. The count of drug-ADR pairs was equal to 1 or 2 for 31,230 combinations and none of them were identified as a possible signal with the MCA or BCPNN. Similarly, the GPS detected a possible signal in none of the combinations where the count was equal to 1 but in 7.5% of the combinations where the count was equal to 2. The RORCI and PRRCI detected a possible signal in more than half of the combinations where the count was equal to 1 or 2. When the pairwise agreement on whether or not a drug-ADR combination satisfied the criteria for a possible signal was assessed for the 38,731 combinations, the concordance measure kappa was greater than 0.9 between the MCA and BCPNN and between the RORCI and PRRCI. Kappa was around 0.6 between the GPS and MCA and between the GPS and BCPNN. Otherwise, kappa was smaller than 0.2., Conclusions: The drug-ADR combinations detected as a possible signal vary between different methodologies., (Copyright 2004 John Wiley & Sons, Ltd.)

Purpose: To compare the effectiveness and safety of reduced or standard daily doses of direct oral anticoagulants (DOACs) with warfarin in Japanese patients with nonvalvular atrial fibrillation (NVAF). We used post-hoc analyses to identify patient groups that could benefit from reduced-dose DOACs. Patients and Methods: Using the National Database of Health Insurance Claims and Specific Health Checkups of Japan, we identified 944,776 patients with NVAF who had started an oral anticoagulant after at least one year of non-use between April 2011 and March 2016. We matched patients taking any, reduced, or standard doses of DOACs 1:1 with those taking warfarin. We measured treatment effectiveness based on admission due to stroke or systemic embolism (S/SE) and safety based on admission due to any bleeding (defined as major bleeding, MB). We compared both outcomes between DOACs and warfarin using the Cox proportional hazards model. We used post-hoc analysis to match patients receiving reduced-dose DOACs to those receiving standard-dose DOACs and compared treatment effectiveness and safety. Results: More than half of patients receiving DOACs used a reduced dose. The occurrences of S/SE and MB in patients receiving any, reduced, or standard doses of DOACs were equal to or lower than those receiving warfarin. In the post-hoc analysis, the risk of S/SE and MB was similar between reduced and standard doses of DOACs except for those with a history of cerebral infarction and CHA2DS2-VASc score ≥ 3, where the risk of S/SE was lower for reduced doses of any and individual DOACs. Conclusion: Findings from the current study are consistent with recent Asian and global studies but different from most studies conducted in North America and Europe, where patients receiving a reduced dose of DOACs had an increased risk of S/SE. Future studies should test the reproducibility of results from the current study. [ABSTRACT FROM AUTHOR]

Purpose The safety of nonsteroidal anti‐inflammatory drugs (NSAIDs) commonly used in Asia‐Pacific countries has had limited study. We assessed the risk of hospitalization for gastrointestinal events with loxoprofen and mefenamic acid compared with other NSAIDs in Asia‐Pacific populations. Methods: We conducted a cohort study using a distributed network with a common data model in Australia, Hong Kong, Japan, Korea, and Taiwan. We included patients who initiated diclofenac, loxoprofen, mefenamic acid, or celecoxib and followed them until their first gastrointestinal hospitalization, switch or discontinuation of medication, disenrollment, or end of database coverage. We used Cox proportional hazards models to assess hospitalization risk. Results: We identified 9879 patients in Japan, 70 492 in Taiwan, 263 741 in Korea, and 246 in Hong Kong who initiated an NSAID, and 44 013 patients in Australia, a predominantly Caucasian population. The incidence of gastrointestinal hospitalization was 25.6 per 1000 person‐years in Japan, 32.8 in Taiwan, 11.5 in Korea, 484.5 in Hong Kong, and 35.6 in Australia. Compared with diclofenac, the risk of gastrointestinal events with loxoprofen was significantly lower in Korea (hazards ratio, 0.37; 95% CI, 0.25‐0.54) but not in Japan (1.65; 95% CI, 0.47‐5.78). The risk of gastrointestinal events with mefenamic acid was significantly lower in Taiwan (0.45; 95% CI, 0.26‐0.78) and Korea (0.11; 95% CI, 0.05‐0.27) but not Hong Kong (2.16; 95% CI, 0.28‐16.87), compared with diclofenac. Conclusions: Compared with diclofenac, loxoprofen was associated with a lower risk of gastrointestinal hospitalizations in Korea and mefenamic acid with a lower risk in Taiwan and Korea. [ABSTRACT FROM AUTHOR]

Background Prescription sequence symmetry analysis (PSSA) is a signal detection method for adverse drug events. Its capacity to consistently detect adverse drug events across different settings has not been tested. We aimed to determine the consistency of PSSA results for detecting positive and negative control adverse drug events across different settings. Methods Using a distributed network model, we analyzed prescription dispensing data using PSSA in Australia, Hong Kong, Japan, Korea, and Taiwan. Positive control was amiodarone and thyroxine, as a marker of amiodarone-induced hypothyroidism, a known adverse event with a clear temporal relationship to amiodarone initiation. Negative controls were amiodarone and allopurinol, as a marker of amiodarone-induced gout and thyroxine and allopurinol, as a marker of thyroxine-induced gout. Gout is not recorded as an adverse event in product information for either medicine. Adjusted sequence ratios (ASR) were calculated for each country. Pooled estimates were obtained by using the generic inverse variance method. Results A positive association was identified between amiodarone and thyroxine in all settings with a pooled ASR 2.63 (95% confidence interval (CI) 1.47-4.72). Temporal analysis showed the effect occurred within the first few weeks of treatment. No significant associations were found for the negative controls in any setting; pooled ASR were 0.76 (95%CI 0.62-0.93) and 0.98 (95%CI 0.85-1.12) for amiodarone-allopurinol and thyroxine-allopurinol, respectively. Conclusion Despite different health settings, different populations, and different patterns of medicine utilization, PSSA gave consistent estimates across countries for a well-known positive association and two negative control adverse events. © 2015 The Authors Pharmacoepidemiology and Drug Safety Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Purpose: To assess the association between statins and diverse adverse events in Japanese population. Methods: New users of statin who started statin after 6-month period of non-use were identified in 68 hospitals between January 2008 and July 2010. In addition to the random sample subcohort, we selected additional subcohort members to make the stratified sample subcohort have at least one patient in all subgroups stratified by each combination of statin and hospital. By abstraction from medical records, detailed information was obtained for all potential cases and pre-selected subcohort members. The event review committee consisting of 3 specialists judged whether possible cases met the definition of one of the adverse events of interest, and for adjudicated cases the committee further judged whether statin was a certain, probable or possible cause of the occurrence of the event. Adjusted for covariates including age, gender, status of “switcher”, use of high daily dose and comorbidities at baseline, hazard ratio (HR) was estimated by the Cox proportional hazards model with Barlow’s weighting method. Data were also analyzed by the method proposed by Breslow in 2009. Results: A total of 6,877 new users of a statin were identified (median age: 66 years; males: 52%). The hazard ratios of increase in serum creatinine for atorvastatin and fluvastatin have wide confidence intervals, but both of the point estimates were around 2.5. Estimates of hazard ratios by the method of Barlow (1999) were similar to those by the method of Breslow (2009). Conclusions: Use of statin was not associated with a significant increased risk for renal, liver and muscle events. However, the hazard ratio of increase in serum creatinine tended to be high with atorvastatin and fluvastatin to require further studies. [ABSTRACT FROM AUTHOR]

Background: For the pending National Claims Database in Japan, researchers will not have access to death information in the enrollment files. We developed and evaluated a claims-based definition of death. Methodology/Principal Findings: We used healthcare claims and enrollment data between January 2005 and August 2009 for 195,193 beneficiaries aged 20 to 74 in 3 private health insurance unions. We developed claims-based definitions of death using discharge or disease status and Charlson comorbidity index (CCI). We calculated sensitivity, specificity and positive predictive values (PPVs) using the enrollment data as a gold standard in the overall population and subgroups divided by demographic and other factors. We also assessed bias and precision in two example studies where an outcome was death. The definition based on the combination of discharge/disease status and CCI provided moderate sensitivity (around 60%) and high specificity (99.99%) and high PPVs (94.8%). In most subgroups, sensitivity of the preferred definition was also around 60% but varied from 28 to 91%. In an example study comparing death rates between two anticancer drug classes, the claims-based definition provided valid and precise hazard ratios (HRs). In another example study comparing two classes of anti-depressants, the HR with the claims-based definition was biased and had lower precision than that with the gold standard definition. Conclusions/Significance: The claims-based definitions of death developed in this study had high specificity and PPVs while sensitivity was around 60%. The definitions will be useful in future studies when used with attention to the possible fluctuation of sensitivity in some subpopulations. [ABSTRACT FROM AUTHOR]

The use of antipsychotic medications (APMs) could be different among countries due to availability, approved indications, characteristics and clinical practice. However, there is limited literature providing comparisons of APMs use among countries. To examine trends in antipsychotic prescribing in Taiwan, Hong Kong, Japan, and the United States, we conducted a cross-national study from 2002 to 2014 b y using the distributed network approach with common data model. We included all patients who had at least a record of antipsychotic prescription in this study, and defined patients without previous exposure of antipsychotics for 6 months before the index date as new users for incidence estimation. We calculated the incidence, prevalence, and prescription rate of each medication by calendar year. Among older patients, sulpiride was the most incident [incidence rate (IR) 11.0–23.3) and prevalent [prevalence rate (PR) 11.9–14.3) APM in Taiwan, and most prevalent (PR 2.5–3.9) in Japan. Quetiapine and haloperidol were most common in the United States (IR 8.1–9.5; PR 18.0–18.4) and Hong Kong (PR 8.8–13.7; PR 10.6–12.7), respectively. The trend of quetiapine use was increasing in Taiwan, Hong Kong and the United States. As compared to older patients, the younger patients had more propensity to be prescribed second-generation APM for treatment in four countries. Trends in antipsychotic prescribing varied among countries. Quetiapine use was most prevalent in the United States and increasing in Taiwan and Hong Kong. The increasing use of quetiapine in the elderly patients might be due to its safety profile compared to other APMs. [ABSTRACT FROM AUTHOR]