Tissue-specific and endogenous protein labeling with split fluorescent proteins.

The ability to label proteins by fusion with genetically encoded fluorescent proteins is a powerful tool for understanding dynamic biological processes. However, current approaches for expressing fluorescent protein fusions possess drawbacks, especially at the whole organism level. Expression by transgenesis risks potential overexpression artifacts while fluorescent protein insertion at endogenous loci is technically difficult and, more importantly, does not allow for tissue-specific study of broadly expressed proteins. To overcome these limitations, we have adopted the split fluorescent protein system mNeonGreen21-10/11 (split-mNG2) to achieve tissue-specific and endogenous protein labeling in zebrafish. In our approach, mNG21-10 is expressed under a tissue-specific promoter using standard transgenesis while mNG211 is inserted into protein-coding genes of interest using CRISPR/Cas-directed gene editing. Each mNG2 fragment on its own is not fluorescent, but when co-expressed the fragments self-assemble into a fluorescent complex. Here, we report successful use of split-mNG2 to achieve differential labeling of the cytoskeleton genes tubb4b and krt8 in various tissues. We also demonstrate that by anchoring the mNG21-10 component to specific cellular compartments, the split-mNG2 system can be used to manipulate protein function. Our approach should be broadly useful for a wide range of applications.

Atypical RhoUV GTPases in development and disease.

RhoU and RhoV are members of the Rho family of small GTPases that comprise their own subfamily. RhoUV GTPases are classified as atypical due to the kinetics of their GTP/GDP binding cycles. They also possess unique N- and C-termini that regulate their subcellular localization and activity. RhoU and RhoV have been linked to cytoskeletal regulation, cell adhesion, and cell migration. They each exhibit distinct expression patterns during embryonic development and diseases such as cancer metastasis, suggesting they have specialized functions. In this review, we will discuss the known functions of RhoU and RhoV, with a focus on their roles in early development, organogenesis, and disease.

Endodermal cells use contact inhibition of locomotion to achieve uniform cell dispersal during zebrafish gastrulation.

The endoderm is one of the three primary germ layers that ultimately gives rise to the gastrointestinal and respiratory epithelia and other tissues. In zebrafish and other vertebrates, endodermal cells are initially highly migratory with only transient interactions among one other, but later converge together to form an epithelial sheet. Here, we show that during their early, migratory phase, endodermal cells actively avoid each other through contact inhibition of locomotion (CIL), a characteristic response consisting of 1) actin depolymerization and membrane retraction at the site of contact, 2) preferential actin polymerization along a cell-free edge, and 3) reorientation of migration away from the other cell. We found that this response is dependent on the Rho GTPase RhoA and EphA/ephrin-A signaling - expression of dominant-negative (DN) RhoA or treatment with the EphA inhibitor dasatinib resulted in behaviors consistent with loss of CIL, including increased contact duration times and decreased likelihood of migration reorientation after contact. Computational modeling predicted that CIL is required to achieve the efficient and uniform dispersal characteristic of endodermal cells. Consistent with our model, we found that loss of CIL via DN RhoA expression resulted in irregular clustering of cells within the endoderm. Together, our results suggest that endodermal cells use EphA2- and RhoA-dependent CIL as a cell dispersal and spacing mechanism, demonstrating how local interactions can give rise to tissue-scale patterns.

Clinical outcomes: endoscopic resection of duodenal ampullary lesions.

Background: Ampullary adenomas are lesions at the duodenum's major papilla commonly associated with familial adenomatous polyposis (FAP) but may also occur sporadically. Historically, ampullary adenomas were removed surgically, however endoscopic resection has become the preferred method of resection. Most of the literature on management of ampullary adenomas are small single-center retrospective reviews. The objective of this study is to describe endoscopic papillectomy outcomes to further refine management guidelines. Methods: This is a retrospective study of patients who underwent endoscopic papillectomy. Demographic data were included. Details regarding lesions and procedures were also collected, including endoscopic impression, size, resection method and adjunctive therapies. Chi-square, Kruskal-Wallis rank-sum, and t-tests were performed. Results: A total of 90 patients were included. 60% patients (54 of 90) had pathology-proven adenomas. 14.4% of all lesions (13 of 90) and 18.5% of adenomas (10 of 54) were treated with APC. Among APC-treated lesions, 36.4% developed recurrence (4 of 11) vs. 7.1% developed residual lesion (1 of 14) (P=0.019). 15.6% of all lesions (14 of 90) and 18.5% of adenomas (10 of 54) reported complications, and the most common was pancreatitis (11.1% and 5.6%). Median follow-up time was 8 months for all lesions and 14 months (range, 1-177 months) for adenomas, with time to recurrence 30 and 31 months (range, 1-137 months), respectively. Recurrence was observed in 16.7% of all lesions (15 of 90) and 20.4% of adenomas (11 of 54). Endoscopic success was observed in 69.2% of all lesions (54 of 78) and 71.4% of adenomas (35 of 49) after removing patients lost to follow-up. Conclusions: Endoscopic papillectomy is an effective method for managing duodenal adenomas. Pathology-proven adenoma should undergo surveillance for at least 31 months. Lesions treated with APC may require closer follow-up and for a prolonged period.

COVID-19-Associated Liver Injury.

This review analyzes data regarding liver injury associated with COVID-19 infection. We discuss reported effects on the liver from both COVID-19 and COVID-19 treatment as well as pathophysiology, review the potential role of drug-induced liver injury as an etiology of COVID-19-associated liver injury, and touch on other reports of significant outcomes including COVID-19 cholangiopathy and autoimmune hepatitis. Finally, we review the implications of COVID-19 infection in liver transplant recipients.

Immunotherapy Use Prior to Liver Transplant in Patients with Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide, and its incidence has increased rapidly in the United States over the past two decades. Liver transplant is considered curative, but is not always possible, and pre-transplant immunotherapy is of great interest as a modality for downstaging the tumor burden. We present a review of the literature on pre-liver transplant immunotherapy use in patients with HCC. Our literature search queried publications in Ovid MEDLINE, Ovid Embase, and Web of Science, and ultimately identified 24 original research publications to be included for analysis. We found that the role of PD-1 and PD-L1 in risk stratification for rejection is of special interest to researchers, and ongoing randomized clinical trials PLENTY and Dulect 2020-1 will provide insight into the role of PD-1 and PD-L1 in liver transplant management in the future. This literature search and the resulting review represents the most thorough collection, analysis, and presentation of the literature on the subject to date.

Alcohol-associated liver disease predicts increased post-liver transplant opioid use.

BACKGROUND: Alcohol-associated liver disease (ALD) is a rising indication for liver transplantation (LT). Prolonged opioid use after LT leads to increased graft loss and mortality. The aim is to determine if patients transplanted with a primary diagnosis of ALD had higher risk of post-LT opioid use (p-LTOU) compared to non-ALD patients. METHODS: This is a retrospective study of patients who underwent LT between 2015 and 2018 at Medstar Georgetown Transplant Institute. Patients with prolonged hospitalization post-LT (>90 days), death within 90 days post-LT, and re-transplants were excluded. RESULTS: Two hundred and ninety seven patients were transplanted, among 29% for indications of ALD. ALD patients were younger (52 vs. 56 years), more likely to be male (76% vs. 61%), Caucasian (71% vs. 44%), have higher MELD (28.8±8.8 vs. 25±8.8), and psychiatric disease than non-ALD patients (P < .05). There was no difference in pre-LT use of opioids, tobacco, marijuana, or illicit drugs between ALD and non-ALD patients. Pre-LT opioid use (OR = 11.7, P < .001), ALD (OR = 2.5, P = .01), and MELD score (OR = .95, P = .02) independently predicted 90-day p-LTOU. CONCLUSIONS: ALD, pre-LT opioid use, and MELD score independently predict p-LTOU. Special attention should be paid to identify post-LT prolonged opioid use in ALD patients.

Highlights of the drug-induced liver injury literature for 2021.

INTRODUCTION: In 2021, over 3,000 articles on Drug-Induced Liver Injury (DILI) were published, nearly doubling the annual number compared to 2011. This review selected DILI articles from 2021 we felt held the greatest interest and clinical relevance. AREAS COVERED: A literature search was conducted using PubMed between 1 March 2021 and 28 February 2022. 86 articles were included. This review discusses new and established cases of hepatotoxins, including new FDA approvals and COVID-19 therapeutics. Developments in biomarkers and causality assessment methods are discussed. Updates from registries are also explored. EXPERT OPINION: DILI diagnosis and prognostication remain challenging. Roussel Uclaf Causality Assessment Method (RUCAM) is the best option for determining causality and has been increasingly accepted by clinicians. Revised Electronic Causality Assessment Method (RECAM) may be more user-friendly and accurate but requires further validation. Quantitative systems pharmacology methods, such as DILIsym, are increasingly used to predict hepatotoxicity. Oncotherapeutic agents represent many newly approved and described causes of DILI. Such hepatotoxicity is deemed acceptable relative to the benefit these drugs offer. Drugs developed for non-life-threatening disorders may not show a favorable benefit-to-risk ratio and will be more difficult to approve. As the COVID-19 landscape evolves, its effect on DILI deserves further investigation.

Real-world incidence of venetoclax toxicities in British Columbia.

INTRODUCTION: Venetoclax is used to treat relapsed/refractory chronic lymphocytic leukemia (r/r CLL). Tumour lysis syndrome (TLS) is a serious toxicity associated with venetoclax, and real-world studies suggest that the incidence may be higher than in clinical trials. The purpose of this study is to describe the incidence of venetoclax toxicities in British Columbia (BC). METHODS: Retrospective review of electronic medical charts for patient characteristics and clinical outcomes of patients treated with venetoclax for r/r CLL in BC. Patients were classified according to their risk for developing TLS. The incidence of TLS was categorized based on laboratory metrics or clinical diagnosis. Other non-TLS toxicities were also collected. RESULTS: Of 33 patients identified, 40%, 33%, and 27% were at low, intermediate, and high risk for TLS, respectively. Laboratory TLS occurred in 1/33 patients (3%), and no clinical TLS was reported. Grade 3 or 4 toxicities occurred in 19/33 patients (58%). Of these, neutropenia was the most common, occurring in 16 patients (84%) followed by thrombocytopenia, which occurred in 8 patients (42%). CONCLUSIONS: The incidence of TLS in patients treated with venetoclax for r/r CLL in BC was lower than in other real-world studies. Findings may warrant further investigation to determine if the higher incidence of TLS in real-world reports may be mitigated through modifying TLS risk categorization and associated prophylactic measures. Neutropenia was the most common grade 3 or 4 venetoclax toxicity reported, and the incidence in BC is comparable to other centres.

Patient-Physician Racial Concordance Associated with Improved Healthcare Use and Lower Healthcare Expenditures in Minority Populations.

BACKGROUND: Racial concordance between patients and clinician has been linked to improved satisfaction and patient outcomes. OBJECTIVES: (1) To examine the likelihood of clinician-patient racial concordance in non-Hispanic White, non-Hispanic Black, Asian, and Hispanic patients and (2) to evaluate the impact of patient-clinician race concordance on healthcare use and expenditures within each racial ethnic group. METHODS: We analyzed data from the 2010-2016 Medical Expenditure Panel Survey (MEPS). We used bivariate and multivariate models to assess the association between patient-clinician race concordance and emergency department (ED) use, hospitalizations, and total healthcare expenses, controlling for patient socio-demographic factors, insurance coverage, health status, and survey year fixed effects. RESULTS: Of the 50,626 adults in the analysis sample, 32,350 had racial concordance with their clinician. Among Asian and Hispanic patients, low income, less education, and non-private insurance were associated with an increased likelihood of patient-clinician racial concordance. Emergency department use was lower among Whites and Hispanics with concordant clinicians compared to those without a discordant clinician (15.6% vs. 17.3%, p = 0.02 and 12.9% vs. 16.2%, p = 0.01 respectively). Total healthcare expenditures were lower among Black, Asian, and Hispanic patients with race-concordant clinicians than those with discordant clinicians (14%, 34%, and 20%, p < 0.001 respectively). CONCLUSIONS: These results add to the body of evidence supporting the hypothesis that racial concordance contributes to a more effective therapeutic relationship and improved healthcare. These results emphasize the need for medical education surrounding cultural humility and the importance of diversifying the healthcare workforce.

Herbal and dietary supplement induced liver injury: Highlights from the recent literature.

Herbal-induced liver injury (HILI) is an important and increasingly concerning cause of liver toxicity, and this study presents recent updates to the literature. An extensive literature review was conducted encompassing September 2019 through March 2021. Studies with clinically significant findings were analyzed and included in this review. We emphasized those studies that provided a causality assessment methodology, such as Roussel Uclaf Causality Assessment Method scores. Our review includes reports of individual herbals, including Garcinia cambogia, green tea extract, kratom as well as classes such as performance enhancing supplements, Traditional Chinese medicine, Ayurvedic medicine and herbal contamination. Newly described herbals include ashwagandha, boldo, skyfruit, and 'Thermo gun'. Several studies discussing data from national registries, including the United States Drug-Induced Liver Injury (DILI) Network, Spanish DILI Registry, and Latin American DILI Network were incorporated. There has also been a continued interest in hepatoprotection, with promising use of herbals to counter hepatotoxicity from anti-tubercular medications. We also elucidated the current legal conversation surrounding use of herbals by presenting updates from the Federal Drug Administration. The highlights of the literature over the past year indicate interest in HILI that will continue as the supplement industry in the United States grows.

Drug-Induced Liver Injury: Highlights and Controversies in the Recent Literature.

Drug-induced liver injury (DILI) remains an important, yet challenging diagnosis for physicians. Each year, additional drugs are implicated in DILI and this year was no different, with more than 1400 articles published on the subject. This review examines some of the most significant highlights and controversies in DILI-related research over the past year and their implications for clinical practice. Several new drugs were approved by the US Food and Drug Administration including a number of drugs implicated in causing DILI, particularly among the chemotherapeutic classes. The COVID-19 pandemic was also a major focus of attention in 2020 and we discuss some of the notable aspects of COVID-19-related liver injury and its implications for diagnosing DILI. Updates in diagnostic and causality assessments related to DILI such as the Roussel Uclaf Causality Assessment Method are included, mindful that there is still no single biomarker or diagnostic tool to unequivocally diagnose DILI. Glutamate dehydrogenase received renewed attention as being more specific than alanine aminotransferase. There were a few new reports of previously unrecognized hepatotoxins, including immune modulators and novel gene therapy drugs that we highlight. Updates and new developments of previously described hepatotoxins, such as immune checkpoint inhibitors and anti-tuberculosis drugs are reviewed. Finally, novel technologies such as organoid culture systems to better predict DILI preclinically may be coming of age and determinants of hepatocyte loss, such as calculating PALT are poised to improve our current means of estimating DILI severity and the risk of acute liver failure.

Light-Induced GFP Expression in Zebrafish Embryos using the Optogenetic TAEL/C120 System.

Inducible gene expression systems are an invaluable tool for studying biological processes. Optogenetic expression systems can provide precise control over gene expression timing, location, and amplitude using light as the inducing agent. In this protocol, an optogenetic expression system is used to achieve light-inducible gene expression in zebrafish embryos. This system relies on an engineered transcription factor called TAEL based on a naturally occurring light-activated transcription factor from the bacterium E. litoralis. When illuminated with blue light, TAEL dimerizes, binds to its cognate regulatory element called C120, and activates transcription. This protocol uses transgenic zebrafish embryos that express the TAEL transcription factor under the control of the ubiquitous ubb promoter. At the same time, the C120 regulatory element drives the expression of a fluorescent reporter gene (GFP). Using a simple LED panel to deliver activating blue light, induction of GFP expression can first be detected after 30 min of illumination and reaches a peak of more than 130-fold induction after 3 h of light treatment. Expression induction can be assessed by quantitative real-time PCR (qRT-PCR) and by fluorescence microscopy. This method is a versatile and easy-to-use approach for optogenetic gene expression.

TAEL 2.0: An Improved Optogenetic Expression System for Zebrafish.

Inducible gene expression systems are valuable tools for studying biological processes. We previously developed an optogenetic gene expression system called TAEL that is optimized for use in zebrafish. When illuminated with blue light, TAEL transcription factors dimerize and activate gene expression downstream of the TAEL-responsive C120 promoter. By using light as the inducing agent, the TAEL/C120 system overcomes limitations of traditional inducible expression systems by enabling fine spatial and temporal regulation of gene expression. In this study, we describe ongoing efforts to improve the TAEL/C120 system. We made modifications to both the TAEL transcriptional activator and the C120 regulatory element, collectively referred to as TAEL 2.0. We demonstrate that TAEL 2.0 consistently induces higher levels of reporter gene expression and at a faster rate, but with comparable background and toxicity as the original TAEL system. With these improvements, we were able to create functional stable transgenic lines to express the TAEL 2.0 transcription factor either ubiquitously or with a tissue-specific promoter. We demonstrate that the ubiquitous line in particular can be used to induce expression at late embryonic and larval stages, addressing a major deficiency of the original TAEL system. This improved optogenetic expression system will be a broadly useful resource for the zebrafish community.

Preventable adverse drug events: Descriptive epidemiology.

AIM: Our objective was to identify preventable adverse drug events and factors contributing to their development. METHODS: We performed a retrospective chart review combining data from three prospective multicentre observational studies that assessed emergency department patients for adverse drug events. A clinical pharmacist and physician independently reviewed the charts, extracted data and rated the preventability of each adverse drug event. A third reviewer adjudicated all discordant or uncertain cases. We calculated the proportion of adverse drug events that were deemed preventable, performed multivariable logistic regression to explore the characteristics of patients with preventable events, and identified contributing factors. RESULTS: We reviewed the records of 1 356 adverse drug events in 1 234 patients. Raters considered 869 (64.1%) of adverse drug events probably or definitely preventable. Patients with mental health diagnoses (OR 1.8; 95% CI 1.3-2.5) and diabetes (OR 1.7; 95% CI 1.2-2.4) were more likely to present with preventable events. The medications most commonly implicated in preventable events were warfarin (9.4%), hydrochlorothiazide (4.5%), furosemide (4.0%), insulin (3.9%) and acetylsalicylic acid (2.7%). Common contributing factors included inadequate patient instructions, monitoring and follow-up, and reassessments after medication changes had been made. CONCLUSIONS: Our study suggests that patients with mental health conditions and diabetes require close monitoring. Efforts to address the identified contributing factors are needed.

Frequency of Advanced Cardiac Life Support Medication Use and Association With Survival During In-hospital Cardiac Arrest.

PURPOSE: Cardiopulmonary resuscitation is common in the United States, with >200,000 people experiencing an in-hospital cardiac arrest (IHCA) annually. Recent medication shortages have raised the question of the frequency and type of medication used during cardiac arrest resuscitation. We sought to determine the frequency and quantity of medications used during IHCA. METHODS: This retrospective, single-center, medical record review was performed at a large, urban teaching hospital. Adults ≥18 years old who had an IHCA with confirmed loss of pulse between January 2017 and March 2018 were identified. A standardized data collection tool was used to extract data from the electronic medical record. The primary outcome was the frequency and quantity of medications used during the IHCA. Secondary outcomes included median time to defibrillation and frequency of sodium bicarbonate use, including among patients with end-stage renal disease (ESRD). FINDINGS: Criteria were met for 181 IHCA events. Demographic characteristics were 71% black, 17% white, mean age of 65 years, and 46% women. Epinephrine was given in 86.7% of the arrests, with a mean cumulative dose of 4.2 mg. Sodium bicarbonate was given in 63.5% of the arrests, with a mean cumulative dose of 9.0 g (1.9 amps). Amiodarone was given in 30.9% of the arrests, with a mean cumulative dose of 311.8 mg. Median time to defibrillation was 2 min (interquartile range, 1-4 min). Preexisting ESRD was present in 24.8% of patients, of whom 71.1% received sodium bicarbonate. Sodium bicarbonate administration was associated with a lower likelihood of survival to discharge (odds ratio [OR] = 0.27; 95% CI, 0.11-0.66) as well as a lower rate of return to spontaneous circulation (ROSC) (OR = 0.35; 95% CI, 0.13-0.95). Magnesium administration was associated with a lower rate of ROSC (OR = 0.39; 95% CI, 0.15-0.98). Of note, in patients with preexisting ESRD, no medications were significantly associated with a change in likelihood of survival to discharge or rate of ROSC. In patients without preexisting ESRD, magnesium was associated with a lower rate of ROSC (OR = 0.23; 95% CI, 0.08-0.77). IMPLICATIONS: We found that in a hospital with established rapid response and code blue teams, numerous medications that are not recommended for routine use in cardiac arrest are still administered at significant frequencies. Furthermore, substantial amounts of drugs with known recent shortage are used in IHCA. Inc.

Repeat adverse drug events associated with outpatient medications: a descriptive analysis of 3 observational studies in British Columbia, Canada.

BACKGROUND: Adverse drug events are an important cause of preventable emergency department visits and hospital admissions. We examined repeat adverse drug events associated with outpatient medications resulting in acute care utilization. METHODS: This descriptive analysis combined data from 3 prospective multicentre observational studies, in which clinical pharmacists and physicians independently evaluated patients who visited the emergency department for adverse drug events in 3 hospitals in British Columbia. During these studies, an independent committee adjudicated all discordant and uncertain cases using a standardized algorithm. For the current study, we retrospectively reviewed the medical and research records of all patients 19 years of age and older who had been diagnosed with an adverse drug event during the primary studies to determine the proportion of repeat events. We used multivariable logistic regression to identify factors associated with repeat events; we adjusted for clustering at the hospital level for patient-level analyses and at the patient level for event-level analyses. RESULTS: Among 12 977 patients, 1178 were diagnosed with 1296 adverse drug events at the point of care. Of these events, 32.5% (421 of 1296; 95% confidence interval [CI] 29.8%-35.1%) were repeat events, of which 75.3% (317 of 421; 95% CI 71.1%-79.5%) were deemed probably or definitely preventable as re-exposure to the culprit medication or repeat withdrawal of an indicated medication was inconsistent with best medical practice. Patients presenting with repeat events were more likely to have renal failure (odds ratio [OR] 2.01; 95% CI 1.32%-3.07%) or a mental health diagnosis (OR 1.39; 95% CI 1.02%-1.88%). INTERPRETATION: A high proportion of adverse drug events were repeat events, most of which were deemed preventable. Interventions to ensure that care providers are aware of previously diagnosed adverse drug events when prescribing or dispensing need to be developed and evaluated and may reduce unintentional re-exposures to previously harmful medications.

Risk Factors for Misuse of Prescribed Opioids: A Systematic Review and Meta-Analysis.

STUDY OBJECTIVE: Increasing opioid prescribing has been linked to an epidemic of opioid misuse. Our objective is to synthesize the available evidence about patient-, prescriber-, medication-, and system-level risk factors for developing misuse among patients prescribed opioids for noncancer pain. METHODS: We performed a systematic search of the scientific and gray literature for studies reporting on risk factors for prescription opioid misuse. Two reviewers independently reviewed titles, abstracts, and full texts; extracted data; and assessed study quality. We excluded studies with greater than 50% cancer patients, palliative patients, and illicit opioid initiation. When possible, we synthesized the effect sizes of dichotomous risk factors and their associations with opioid misuse, using inverse-variance random-effects meta-analysis. We calculated the mean difference between opioid misusers and nonmisusers for continuous risk factors. When studies lacked homogeneity, we synthesized their results qualitatively. RESULTS: Of 9,629 studies, 65 met our inclusion criteria. Among patients with outpatient opioid prescriptions, the following factors were associated with the development of misuse: any current or previous substance use (odds ratio [OR] 3.55; 95% confidence interval [CI] 2.62 to 4.82), any mental health diagnosis (OR 2.45; 95% CI 1.91 to 3.15), younger age (OR 2.19; 95% CI 1.81 to 2.64), and male sex (OR 1.23; 95% CI 1.10 to 1.36). CONCLUSION: Although clinicians should endeavor to offer alternative pain management strategies to all patients, those who are younger, are male patients, and report a history of or current substance use or mental health diagnoses were associated with a greater risk of developing opioid misuse. Clinicians should consider prioritizing alternative pain management strategies for these higher-risk patients.

Methods for evaluating adverse drug event preventability in emergency department patients.

BACKGROUND: There is a high degree of variability in assessing the preventability of adverse drug events, limiting the ability to compare rates of preventable adverse drug events across different studies. We compared three methods for determining preventability of adverse drug events in emergency department patients and explored their strengths and weaknesses. METHODS: This mixed-methods study enrolled emergency department patients diagnosed with at least one adverse drug event from three prior prospective studies. A clinical pharmacist and physician reviewed the medical and research records of all patients, and independently rated each event's preventability using a "best practice-based" approach, an "error-based" approach, and an "algorithm-based" approach. Raters discussed discordant ratings until reaching consensus. We assessed the inter-rater agreement between clinicians using the same assessment method, and between different assessment methods using Cohen's kappa with 95% confidence intervals (95% CI). Qualitative researchers observed discussions, took field notes, and reviewed free text comments made by clinicians in a "comment" box in the data collection form. We developed a coding structure and iteratively analyzed qualitative data for emerging themes regarding the application of each preventability assessment method using NVivo. RESULTS: Among 1356 adverse drug events, a best practice-based approach rated 64.1% (95% CI: 61.5-66.6%) of events as preventable, an error-based approach rated 64.3% (95% CI: 61.8-66.9%) of events as preventable, and an algorithm-based approach rated 68.8% (95% CI: 66.1-71.1%) of events as preventable. When applying the same method, the inter-rater agreement between clinicians was 0.53 (95% CI: 0.48-0.59), 0.55 (95%CI: 0.50-0.60) and 0.55 (95% CI: 0.49-0.55) for the best practice-, error-, and algorithm-based approaches, respectively. The inter-rater agreement between different assessment methods using consensus ratings for each ranged between 0.88 (95% CI 0.85-0.91) and 0.99 (95% CI 0.98-1.00). Compared to a best practice-based assessment, clinicians believed the algorithm-based assessment was too rigid. It did not account for the complexities of and variations in clinical practice, and frequently was too definitive when assigning preventability ratings. CONCLUSION: There was good agreement between all three methods of determining the preventability of adverse drug events. However, clinicians found the algorithmic approach constraining, and preferred a best practice-based assessment method.