Temporal trends and patterns in carbamazepine use, related severe cutaneous adverse reactions, and HLA-B*15:02 screening: A nationwide study

Disparities in Genetic Testing for Neurologic Disorders

BACKGROUND AND OBJECTIVES

Genetic testing is now the standard of care for many neurologic conditions. Health care disparities are unfortunately widespread in the US health care system, but disparities in the utilization of genetic testing for neurologic conditions have not been studied. We tested the hypothesis that access to and results of genetic testing vary according to race, ethnicity, sex, socioeconomic status, and insurance status for adults with neurologic conditions.

METHODS

We analyzed retrospective data from patients who underwent genetic evaluation and testing through our institution's neurogenetics program. We tested for differences between demographic groups in 3 steps of a genetic evaluation pathway: (1) attending a neurogenetic evaluation, (2) completing genetic testing, and (3) receiving a diagnostic result. We compared patients on this genetic evaluation pathway with the population of all neurology outpatients at our institution, using univariate and multivariable logistic regression analyses.

RESULTS

Between 2015 and 2022, a total of 128,440 patients were seen in our outpatient neurology clinics and 2,540 patients underwent genetic evaluation. Black patients were less than half as likely as White patients to be evaluated (odds ratio [OR] 0.49, p < 0.001), and this disparity was similar after controlling for other demographic factors in multivariable analysis. Patients from the least wealthy quartile of zip codes were also less likely to be evaluated (OR 0.67, p < 0.001). Among patients who underwent evaluation, there were no disparities in the likelihood of completing genetic testing, nor in the likelihood of a diagnostic result after adjusting for age. Analyses restricted to specific indications for genetic testing supported these findings.

DISCUSSION

We observed unequal utilization of our clinical neurogenetics program for patients from marginalized and minoritized demographic groups, especially Black patients. Among patients who do undergo evaluation, all groups benefit similarly from genetic testing when it is indicated. Understanding and removing barriers to accessing genetic testing will be essential to health care equity and optimal care for all patients with neurologic disorders.

A highlight on carbamazepine-induced adverse drug reactions in Saudi Arabia: a retrospective medical records-based study

The link between human leukocyte antigen (HLA) alleles and carbamazepine-induced cutaneous, respiratory, and gastrointestinal adverse drug reactions (ADR) has created a window of opportunity for preventing certain forms of cutaneous adverse drug reactions (cADRs); however, there is not enough data to make pharmacogenomic recommendations that can be implemented globally. The aim of this study is to assess and document carbamazepine-induced adverse reactions among prescribed Saudi/non-Saudi patients. A retrospective chart review was performed for patients who received carbamazepine (CBZ) in the period between 2016 and 2020, in the Kingdom of Saudi Arabia. Data were gathered and descriptive statistical analyses were performed on the data for the study sample. Comparisons were made using the chi-square test or independent samples' t-test. Statistical significance was considered at p < .05. All statistical analyses were performed using IBM SPSS 21.0 (Armonk, NY; IBM Corp). Results from multivariate logistic regression analyses showed that higher likelihood of carbamazepine-induced adverse reactions was significantly associated with younger age, OR = 0.82, 95% CI (0.74, 0.90); p < 0.001. Patients who were prescribed CBZ for reasons other than epilepsy or seizures were significantly more likely to develop carbamazepine-induced adverse reactions (epilepsy vs. other; OR = 0.63, p = 0.013; seizures vs. other; OR = 0.59, p = 0.018). Gender or medication duration were not related to carbamazepine-induced adverse reactions (p > 0.05). The findings of this study are comparable with those of other studies assessing carbamazepine-associated adverse reactions in children and adults. Recommendations include genetic prescreening, educating patients and parents on the possibility of adverse reactions, and routine laboratory monitoring.

Lifetime risk, life expectancy, loss-of-life expectancy and lifetime healthcare expenditure for Stevens-Johnson syndrome/toxic epidermal necrolysis in Taiwan: follow-up of a nationwide cohort from 2008 to 2019

BACKGROUND

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) not only cause acute, devastating mucocutaneous reactions but also have long-lasting implications on survivors' lives.

OBJECTIVES

To quantify the lifetime burden of SJS/TEN.

METHODS

The cumulative incidence rate (CIR), life expectancy (LE), loss-of-life expectancy (LoLE) and lifetime healthcare expenditure (HE) for SJS/TEN were estimated over the period from 2008 to 2019 using data from the National Health Insurance Research Database of Taiwan and life tables of vital statistics.

RESULTS

In this nationwide cohort of 6552 incident SJS/TEN cases, a trend towards a decrease in the CIR was observed between 2008 and 2019. Compared with the general population, patients with SJS/TEN experience a tremendous loss of 9.43 (1.06) [mean (SEM)] years of LE after diagnosis of SJS/TEN. Male patients with SJS/TEN had higher LoLE [10.74 (1.22) vs. 7.69 (1.43) years] and annual HE than females. Younger age at diagnosis of SJS/TEN was associated with longer LE but greater LoLE and higher lifetime HE. Patients with intensive care unit admission on diagnosis, malignancy, diabetes mellitus, end-stage renal disease and SJS/TEN-associated sequelae experienced substantially greater LoLE and HE per life year.

CONCLUSIONS

Patients with SJS/TEN suffer substantial loss-of-LE and HE, particularly young patients, compared with the general population. These data provide a reference estimate of the lifetime burden of SJS/TEN to help health authorities evaluate the cost-effectiveness of future preventive and treatment strategies to minimize the burden of SJS/TEN.

Awareness of HLA-B* 15:02 screening in trigeminal neuralgia and the gene screening policy among dentists in Southern Thailand

OBJECTIVES

To determine the factors associated with public hospital dentists' awareness of HLA-B*15:02 screening in trigeminal neuralgia (TN) and the national gene screening policy in Thailand.

METHODS

Cross-sectional study. A validated questionnaire was distributed to public hospital dentists with at least 1 year of practice in Southern Thailand (n = 760) to assess their knowledge of TN, carbamazepine (CBZ) use, awareness of HLA-B*15:02 screening, and the gene screening policy.

RESULTS

A total of 385 dentists participated (50.7% response rate); 81.3% of respondents were aware of HLA-B*15:02 screening. However, 18.7% of dentists were not aware of the importance of gene testing. Furthermore, dentists who were aware of gene screening had significantly better knowledge of TN diagnosis and CBZ use than "unaware" dentists. Awareness of HLA-B*15:02 screening was also significantly associated with dental specialty. Moreover, 80.5% of respondents were not aware of the gene screening policy. The primary problems related to the policy were its inefficient publication, poor implementation, and lack of clinical practice guidelines (CPGs) to encourage dentists to follow the policy and prescribe gene tests.

CONCLUSION

While most hospital dentists were aware of the necessity of HLA-B*15:02 screening prior to prescribing CBZ in TN, the majority were unaware of the national gene screening policy. Dental specialty and knowledge were associated with awareness of HLA-B*15:02 screening.

Role of human leukocyte antigen in anti-epileptic drugs-induced Stevens-Johnson Syndrome/toxic epidermal necrolysis: A meta-analysis

PURPOSE

Antiepileptic drugs (AEDs) are extensively used to manage epilepsy and other comorbidities associated with seizures. Human Leukocyte Antigen (HLA) has a strong association with AED-induced severe cutaneous adverse drug reactions.

OBJECTIVE

We aimed to perform a systematic review and meta-analysis to identify, critically evaluate, and synthesize the best possible evidence on HLA-associated AED-induced Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN).

METHODS

MEDLINE/PubMed, Scopus, and the Cochrane Library were searched for literature from inception up to July 2022. We included case control studies analyzing association between HLA and AED-induced SJS/TEN. We assessed the studies' risk of bias in using Quality of genetic studies (Q-genie) tool. Outcomes focused on association (risk) between HLA and AED-induced SJS/TEN. The estimated risk was presented in the form of odds ratio (OR).

RESULTS

We included 37 studies (51,422 participants; 7027 cases and 44,395 controls). There was a significantly higher risk of Carbamazepine-induced SJS/TEN with HLA-A (OR: 1.50; 95% CI: 1.03 to 2.17), HLA-B (OR: 1.94; 95% CI: 1.45 to 2.58), HLA-C (OR: 7.83; 95% CI: 4.72 to 12.98), and HLA-DRB1 (OR: 2.82; 95% CI: 1.94 to 4.12). Lamotrigine-induced SJS/TEN posed a higher risk with HLA-A (OR: 2.38; 95% CI: 1.26 to 4.46) and HLA-B (OR: 2.79; 95% CI: 1.75 to 4.46). Phenytoin-induced SJS/TEN showed a higher risk with HLA-A (OR: 3.47; 95% CI: 2.17 to 5.56), HLA-B (OR: 1.72; 95% CI: 1.38 to 2.15), and HLA-C (OR: 2.92; 95% CI: 1.77 to 4.83). Phenobarbital-induced SJS/TEN had a higher risk with HLA-A (OR: 6.98; 95% CI: 1.81 to 26.84), HLA-B (OR: 2.40; 95% CI: 1.39 to 4.17), and HLA-C (OR: 3.37; 95% CI: 1.03 to 11.01). Zonisamide-induced SJS/TEN was significantly associated with HLA-A*02:07 (OR: 9.77; 95% CI: 3.07 to 31.1), HLA-B*46:01 (OR: 6.73; 95% CI: 2.12 to 21.36), and HLA-DRB1×08:03 (OR: 3.78; 95% CI: 1.20 to 11.97). All other alleles of HLA were observed to have a non-significant association with AED-induced SJS/TEN. All included studies were of good quality, with a score of >50 and a mean score of 54.96 out of 77.

CONCLUSION

Our study showed a significant association between few variants of HLA alleles and AED-induced SJS/TEN. Evidences from our study could help in population-based studies and in implementation of individualized treatment regimens. These findings could be part of translational research helping in precision therapy.

Practical Implementation of Genetics: New Concepts in Immunogenomics to Predict, Prevent, and Diagnose Drug Hypersensitivity

Delayed drug hypersensitivities are CD8⁺ T cell-mediated reactions associated with up to 50% mortality. Human leukocyte antigen (HLA) alleles are known to predispose disease and are specific to drug, reaction, and patient ethnicity. Pretreatment screening is recommended for a handful of the strongest associations to identify and prevent drug use in high-risk patients. However, an incomplete predictive value implicates other HLA-imposed risk factors, and low carriage of many identified HLA-risk alleles combined with the high cost of sequence-based typing has limited economic viability for similar recommendation of screening across drugs and health care systems. For mitigation, an expanding armory of low-cost polymerase chain reaction-based screens is being developed, and HLA-imposed risk factors are being discovered. These include (1) polymorphic variants of metabolic and endoplasmic reticulum aminopeptidase enzymes toward multiallelic screening with increased predictivity; (2) regulation by immune checkpoint inhibitors, enabling detolerized animal models of human disease; and (3) immunodominant T cell receptors (TCR) on clonally expanded CD8⁺ T cells. For the latter, HLA risk-restricted TCR provides immunogenomic strategies and samples from a single patient to identify novel HLA-risk associations in underserved minority populations, tissue-relevant effector biomarkers toward earlier diagnosis and treatment, and HLA-TCR-presented immunogenic structures to aid future drug development.

Pharmacogenomics of Clozapine-induced agranulocytosis: a systematic review and meta-analysis

Although clozapine is the most effective pharmacotherapy for treatment-resistant schizophrenia, it is under-utilized, and initiation is often delayed. One reason is the occurrence of a potentially fatal adverse reaction, clozapine-induced agranulocytosis (CIA). Identifying genetic variations contributing to CIA would help predict patient risk of developing CIA and personalize treatment. Here, we (1) review existing pharmacogenomic studies of CIA, and (2) conduct meta-analyses to identify targets for clinical implementation. A systematic literature search identified studies that included individuals receiving clozapine who developed CIA and controls who did not. Results showed that individuals carrying the HLA-DRB1*04:02 allele had nearly sixfold (95% CI 2.20–15.80, p_corrected = 0.03) higher odds of CIA with a negative predictive value of 99.3%. Previously unreplicated alleles, TNFb5, HLA-B*59:01, TNFb4, and TNFd3 showed significant associations with CIA after multiple-testing corrections. Our findings suggest that a predictive HLA-DRB1*04:02-based pharmacogenomic test may be promising for clinical implementation but requires further investigation.

Secular Trends in the Incidence, Prevalence, and Medications for Epilepsy from 2007 to 2015 in Taiwan: A Nationwide Population-Based Study

BACKGROUND

Patients with epilepsy have a higher mortality rate than the general population. Up-to-date estimates of epilepsy incidence, prevalence, and medication use are critical to assist policymaking.

METHODS

Using the National Taiwan Insurance Research Database, the standardized incidence and prevalence of epilepsy were estimated in each calendar year from 2007 to 2015. We used the incident cases of epilepsy to analyze the change in prescribing patterns from 2007 to 2015. Joinpoint regression was used to estimate secular trends.

RESULTS

From 2007 to 2015, the age- and sex-standardized incidence decreased from 0.72 (95% confidence interval [CI] 0.70-0.73) to 0.54 (95% CI 0.53-0.55) per 1,000 person-years, giving an annual percentage change (APC) of -2.73 (p < 0.05). Among patients younger than 20 years, the incidence did not change significantly. The age- and sex-standardized prevalence decreased from 6.94 (95% CI 6.90-6.98) to 6.86 (95% CI, 6.82-6.89) per 1,000 people, giving an APC of -0.31 (p < 0.05). However, the prevalence increased in the 35- to 49- and 50- to 64-year age-groups. The most common first-line anticonvulsant was phenytoin in 2007 and valproate in 2015. The use of levetiracetam, clobazam, and valproate increased during the study period, with APCs of 25.48% (95% CI 19.97-31.24), 6.41 (3.09-9.85), and 2.83 (1.51-4.16), respectively. The use of carbamazepine, phenytoin, and topiramate decreased; the APCs were -23.86% (95% CI -25.25 to -22.44), -6.61 (-8.40 to -4.79), and -4.29% (-7.87 to -0.57), respectively.

CONCLUSIONS

The overall prevalence and incidence of epilepsy decreased slightly from 2007 to 2015. The prescribed first-line anticonvulsant also changed over time.

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

Review and Consensus on Pharmacogenomic Testing in Psychiatry

The implementation of pharmacogenomic (PGx) testing in psychiatry remains modest, in part due to divergent perceptions of the quality and completeness of the evidence base and diverse perspectives on the clinical utility of PGx testing among psychiatrists and other healthcare providers. Recognizing the current lack of consensus within the field, the International Society of Psychiatric Genetics assembled a group of experts to conduct a narrative synthesis of the PGx literature, prescribing guidelines, and product labels related to psychotropic medications as well as the key considerations and limitations related to the use of PGx testing in psychiatry. The group concluded that to inform medication selection and dosing of several commonly-used antidepressant and antipsychotic medications, current published evidence, prescribing guidelines, and product labels support the use of PGx testing for 2 cytochrome P450 genes (CYP2D6, CYP2C19). In addition, the evidence supports testing for human leukocyte antigen genes when using the mood stabilizers carbamazepine (HLA-A and HLA-B), oxcarbazepine (HLA-B), and phenytoin (CYP2C9, HLA-B). For valproate, screening for variants in certain genes (POLG, OTC, CSP1) is recommended when a mitochondrial disorder or a urea cycle disorder is suspected. Although barriers to implementing PGx testing remain to be fully resolved, the current trajectory of discovery and innovation in the field suggests these barriers will be overcome and testing will become an important tool in psychiatry.

Challenges and Opportunities in Implementing Pharmacogenetic Testing in Clinical Settings

The clinical implementation of pharmacogenetic biomarkers continues to grow as new genetic variants associated with drug outcomes are discovered and validated. The number of drug labels that contain pharmacogenetic information also continues to expand. Published, peer-reviewed clinical practice guidelines have also been developed to support the implementation of pharmacogenetic tests. Incorporating pharmacogenetic information into health care benefits patients as well as clinicians by improving drug safety and reducing empiricism in drug selection. Barriers to the implementation of pharmacogenetic testing remain. This review explores current pharmacogenetic implementation initiatives with a focus on the challenges of pharmacogenetic implementation and potential opportunities to overcome these challenges.

Using real-world evidence for pharmacovigilance and drug safety-related decision making by a resource-limited health authority: 10 years of experience in Taiwan

PURPOSE

Real-world evidence has become increasingly relevant in regulatory decision making. Compared to large regulatory bodies, the national pharmacovigilance system in Taiwan is still under development, and the aim of this study is to demonstrate how a resource-limited health authority utilizes real-world evidence in decision making.

METHODS

We described different sources of real-world data available in Taiwan and illustrated the structural framework that integrates real-world evidence into Taiwan's national pharmacovigilance system. Additionally, we reviewed real-world studies conducted in the past 10 years and provided examples to show how these studies influenced drug safety-related decision making in Taiwan.

RESULTS

During the past 10 years, real-world evidence used when making drug safety-related regulatory decisions in Taiwan was mainly generated from nationwide claims databases, but other sources of real-world data, such as national registries and large electronic hospital databases, also became available recently. Different types of real-world evidence, including drug utilization studies, risk evaluation studies, and risk minimization measure evaluation studies, have been used to support regulatory decisions in Taiwan.

CONCLUSIONS

Through collaborations between the government and academics, Taiwan has started to integrate real-world evidence into the national pharmacovigilance system. However, future efforts, including linkages between different sources of real-world data and improvements in procedural and methodological practices, are needed to generate more regulatory-quality real-world evidence.

Use of antipsychotics and the risk of acute respiratory failure among adults: A disease risk score-matched nested case-control study

AIMS

Evidence on acute respiratory failure (ARF) from antipsychotics is scant, and only 1 population-based study examined this drug safety issue in chronic obstructive pulmonary disease patients. Antipsychotics have been frequently prescribed off-label in adults, but whether antipsychotic use carries an increased ARF risk among adult patients is uncertain.

METHODS

We adopted a nested case-control study analysing 716 493 adults aged ≥20 years, identified from the Taiwan nationwide healthcare claims records between January 2000 and December 2013. Among the study cohort, 7084 adults with ARF and 12,785 disease risk scored-matched randomly selected controls were analysed. Multivariable logistic regression models were employed to estimate odds ratios of ARF with antipsychotic usages.

RESULTS

Current, recent, and recent past use of antipsychotics was associated with a 2.33-fold (95% confidence interval [CI] = 2.06-2.64), 1.79-fold (95% CI = 1.43-2.25) and 1.41-fold (95% CI = 1.20-1.66) increased risk of ARF, respectively, compared with nonuse, while antipsychotics discontinued >90 days carried no risk. A dose-dependent association was observed with current therapy of antipsychotics (test for trend, P < .001), in which antipsychotic use at >1 defined daily dose yielded the highest risk of 6.53-fold (95% CI = 3.33-12.79). The findings were robust to using carbamazepine as an active comparator.

CONCLUSION

Antipsychotic use was associated with an increased risk of ARF in adult patients. The risk was dose-dependent and markedly higher with current use of antipsychotic agents at doses of 1 defined daily dose and above, <10% of this cohort. Physicians should be vigilant about any respiratory symptoms in patients currently receiving antipsychotics at such dose.

Usage Pattern of Carbamazepine and Associated Severe Cutaneous Adverse Reactions in Singapore Following Implementation of HLA-B*15:02 Genotyping as Standard-of-Care

In April 2013, the Ministry of Health and Health Sciences Authority of Singapore jointly issued recommendations for HLA-B*15:02 genotyping before starting carbamazepine (CBZ) in new patients of Asian ancestry as standard of care. The Ministry of Health also approved a 75% subsidy for HLA-B*15:02 genotyping to all patients on subsidy at public healthcare institutions. To understand the impact of these regulatory decisions, we researched the usage patterns for CBZ and levetiracetam, the trend of Stevens-Johnson syndrome/toxic epidermal necrolysis [Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN)] reports associated with antiepileptic drugs and the take-up rates of HLA-B*15:02 tests in Singapore. In the 5-year post-policy period, we found that the annual number of reported SJS/TEN cases associated with all antiepileptic drugs was significantly decreased by 57% (p = 0.015); SJS/TEN cases associated with CBZ and phenytoin reduced by 92% and 42% respectively. New CBZ users decreased by 31% while new levetiracetam users approximately doubled. The annual number of HLA-B*15:02 tests conducted increased from 444 to approximately 1,200. Regulatory recommendations for HLA-B*15:02 genotyping as standard of care coupled with government subsidy for the test had contributed to a reduction in CBZ SJS/TEN in Singapore by >90%, in line with that observed in other Asian countries with similar policies. Additionally, the number of phenytoin-SJS/TEN cases also declined. Taken together, this represents a successful example of precision medicine through implementation of a genotyping program to reduce a rare but serious adverse drug reaction among at-risk individuals, while preserving the availability of an effective and low-cost medicine for the broader population.

High and variable population prevalence of HLA-B*56:02 in indigenous Australians and relation to phenytoin-associated drug reaction with eosinophilia and systemic symptoms

Phenytoin drug reaction with eosinophilia and systemic symptoms (DRESS) in 3 Aboriginal Australians positive for HLA-B*56:02 has been previously reported. We report the allele frequency of HLA-B*56:02 in 2 South Australian populations, 1 Aboriginal (4.8%, 95% confidence interval 2.4-7.8%) and the other European (0%). We compared the frequency with publicly available information on HLA-B*56:02 status in other Indigenous Australian (n = 4) and European Australian cohorts (n = 1). In the Indigenous Australian cohorts, HLA-B*56:02 allele frequency ranged from 1.3 to 19%. We also describe an additional case of phenytoin DRESS (RegiSCAR DRESS score 7) in an Aboriginal Australian that was associated with HLA-B*56:02 and with CYP2C9*1/*3 genotype. In Aboriginal Australians, phenytoin DRESS appears distinctly linked to HLA-B*56:02 with an allele carriage rate substantially higher than in Europeans, but also with considerable regional variation. Investigations of human leucocyte antigen and other contributing genes and severe adverse drug reactions in understudied non-European populations are required to optimize safe medication use and inform risk mitigation strategies.

A Realistic Review of the Drug-Injury Relief System in Taiwan: Challenges, Lessons, and Achievements

The drug-injury relief system in Taiwan was implemented 20 years ago with the goal of providing timely relief for drug injuries incurred by the proper use of legal drugs. This system utilizes a nonlitigation expert review process to evaluate drug-injury relief applications, and 2,732 applications have been reviewed from 1999-2016. Of these, 1,572 applications received relief payments, an approval rate of 58%. Average review timeframes per application have decreased from 248 days (2003-2011) to 182 days (2012-2016). Most adverse drug reactions (ADRs) for approved cases involved skin and subcutaneous tissue disorders (67%), with allopurinol being the primary culprit drug. A recent decline observed for such ADRs may reflect the influences of promotional activities and policy initiatives carried out according to informed analysis from drug-injury relief applications, which suggests that the drug-injury relief system can also play an important public health role in enhancing drug safety.