Validation of algorithms in studies based on routinely collected health data: general principles.

Clinicians, researchers, regulators, and other decision-makers increasingly rely on evidence from real-world data (RWD), including data routinely accumulating in health and administrative databases. RWD studies often rely on algorithms to operationalize variable definitions. An algorithm is a combination of codes or concepts used to identify persons with a specific health condition or characteristic. Establishing the validity of algorithms is a prerequisite for generating valid study findings that can ultimately inform evidence-based health care. This paper aims to systematize terminology, methods, and practical considerations relevant to the conduct of validation studies of RWD-based algorithms. We discuss measures of algorithm accuracy; gold/reference standard; study size; prioritizing accuracy measures; algorithm portability; and implication for interpretation. Information bias is common in epidemiologic studies, underscoring the importance of transparency in decisions regarding choice and prioritizing measures of algorithm validity. The validity of an algorithm should be judged in the context of a data source, and one size does not fit all. Prioritizing validity measures within a given data source depends on the role of a given variable in the analysis (eligibility criterion, exposure, outcome or covariate). Validation work should be part of routine maintenance of RWD sources.

Infrequent transition to direct oral anticoagulants in patients with cancer.

INTRODUCTION: Pharmacokinetic drug-drug interactions (DDIs) are challenging aspects of direct oral anticoagulant (DOAC) therapy in patients with cancer. We evaluated the prevalence of potential DOAC/antineoplastic agent DDIs and the one-year cumulative incidence of switching from low-molecular-weight heparin (LMWH) to a DOAC in patients with cancer. METHODS: Patients with cancer and an indication of LMWH were included from Herlev and Gentofte Hospital, Denmark, in the 2014-2019 period. Follow-up was initiated when the first dose of LMWH was dispensed. Data were obtained from electronic medical records. One-year cumulative incidence of switching from LMWH to DOAC was estimated using the Aalen-Johansen estimator. Potential DDIs were evaluated using a report from the European Heart Rhythm Association (EHRA) and a review by Hellfritzsch et al. RESULTS. A total of 161 patients were included with a median age of 70.8 (interquartile range: 64.2-76.1) years. The one-year cumulative incidence of switching from LMWH to DOAC was 32% (95% confidence intervals: 21-43%) in patients eligible for DOACs. Using the EHRA report, a total of 24% of antineoplastic agents were not identified. This percentage decreased to 8% using data from Hellfritzsch et al. CONCLUSIONS. In patients with cancer, the one-year cumulative incidence of switching from LMWH to DOAC was less-t 35% in patients eligible for DOAC, revealing a potential for improved anticoagulant treatment. Furthermore, contemporary data elaborated on potential DDIs between DOACs/antineoplastic agents. FUNDING: "Helsefonden" (21-B-0350) and the "Karen Elise Jensens Fonden" (29-4-2021) funded the study. TRIAL REGISTRATION: Not relevant.

Drug-Drug Interactions in the Treatment of Cancer-Associated Venous Thromboembolism with Direct Oral Anticoagulants.

Venous thromboembolism (VTE) is a frequent complication of cancer, and management of cancer-associated thrombosis (CAT) is challenging due to increased risks of bleeding and recurrent VTE. Recent trials have shown an acceptable efficacy and safety of direct oral anticoagulants (DOACs) in the treatment of CAT compared to low-molecular weight heparin. Although DOACs provide an effective and convenient treatment option in CAT, the need to assess the risk of drug-drug interactions (DDI) with antineoplastic therapies poses a barrier to their use in clinical practice. With the aim of supporting the assessment of CAT patients for treatment with DOAC, this review provides a comprehensive overview of the compatibility of antineoplastic therapies with the individual DOACs (apixaban, dabigatran, edoxaban, and rivaroxaban). Using several data sources, we characterized 100 widely used antineoplastic agents with regard to their effect on p-glycoprotein and cytochrome P450, both important in the transport and elimination of DOACs. This enabled us to evaluate 400 "DOAC-antineoplastic agent"-pairs regarding their likelihood to interact (unlikely, potential, or likely), ultimately leading to clinical recommendations on the appropriateness of concomitant use for each pair. A potential or likely DDI was identified for 12% of the evaluated pairs. For nearly all antineoplastic agents, at least one DOAC was considered compatible.

Comparison of international guideline recommendations for the diagnosis of pulmonary embolism.

Pulmonary embolism is one of the leading causes of death due to cardiovascular disease. Timely diagnosis is crucial, but challenging, as the clinical presentation of pulmonary embolism is unspecific and easily mistaken for other common medical emergencies. Clinical prediction rules and D-dimer measurement allow stratification of patients into groups of expected prevalence and are key elements in adequate selection of patients for diagnostic imaging; however, the strengths and weaknesses of the multiple proposed prediction rules, when to measure D-dimer, and which cutoff to apply might be elusive to a significant proportion of physicians. 13 international guidelines authored by medical societies or expert author groups provide recommendations on facets of the diagnostic investigations in suspected pulmonary embolism, some of which are hallmarked by pronounced heterogeneity. This Review summarises key recommendations of each guideline, considers the most recent evidence on the topic, compares guideline recommendations on each facet of the diagnosis of pulmonary embolism, and provides a synthesis on the most common recommendations.

Prophylaxis of Venous Thromboembolism in Children: A Systematic Review.

Venous thromboembolism (VTE) in children is a rare but serious event. Current guidance on pharmacological thromboprophylaxis in children is mostly based on adult studies and expert opinions. The aim of this systematic review was to examine under which conditions children (age ≤ 18 years) would benefit from pharmacological thromboprophylaxis with low molecular weight heparin or unfractionated heparin. Eligible studies included children, who did not receive pharmacological thromboprophylaxis as comparator, and VTE events were radiologically verified. MEDLINE and Embase were searched up to October 3, 2021. Ten studies were included presenting data for 976 children receiving pharmacological thromboprophylaxis. We divided the studies into three categories based on the population studied: children in the intensive care unit (n = 2), children with fractures and/or undergoing surgery (n = 5), and children with systemic disease (n = 3). A lower incidence of VTE was found when pharmacological thromboprophylaxis was used compared with no prophylaxis in children in intensive care unit with central venous catheter and mechanical ventilation (7/27 vs. 13/24), children in the intensive care unit admitted after trauma with a very high risk of VTE based on several risk factors (0/21 vs. 13/96), and children with acute lymphoblastic leukemia treated with L-asparaginase concomitant with steroid and presence of central venous catheter (0/82 vs. 8/121). Pharmacological thromboprophylaxis was not associated with an increased bleeding risk. In conclusion, pharmacological thromboprophylaxis in children is sparsely investigated. Only children with several risk factors for VTE are likely to benefit from pharmacological thromboprophylaxis.

Non-vitamin K antagonist oral anticoagulants, proton pump inhibitors and gastrointestinal bleeds.

OBJECTIVE: To evaluate if proton pump inhibitor (PPI) treatment reduces the risk of upper gastrointestinal bleeding (UGIB) in patients with atrial fibrillation (AF) treated with non-vitamin K antagonist oral anticoagulants (NOACs). DESIGN: We used a common protocol, common data model approach to conduct a cohort study including patients with AF initiated on a NOAC in Stockholm, Denmark and the Netherlands from April 2011 until July 2018. The outcome of interest was a UGIB diagnosed in a secondary care inpatient setting. We used an inverse probability weighted (IPW) Poisson regression to calculate incidence rate ratios (IRRs), contrasting PPI use to no PPI use periods. RESULTS: In 164 290 NOAC users with AF, providing 272 570 years of follow-up and 39 938 years of PPI exposure, 806 patients suffered a UGIB. After IPW, PPI use was associated with lower UGIB rates (IRR: 0.75; 95% CI: 0.59 to 0.95). On an absolute scale, the protective effect was modest, and was found to be largest in high-risk patients, classified as age 75-84 years (number needed to treat for 1 year (NNTY): 787), age ≥85 years (NNTY: 667), HAS-BLED score ≥3 (NNTY: 378) or on concomitant antiplatelet therapy (NNTY: 373). CONCLUSION: Concomitant treatment with a PPI in NOAC-treated patients with AF is associated with a reduced risk of severe UGIB. This indicates that PPI cotreatment can be considered, in particular among the elderly patients, patients with a HAS-BLED score ≥3, and/or in patients on concomitant antiplatelet therapy.

Persistence and adherence to non-vitamin K antagonist oral anticoagulant treatment in patients with atrial fibrillation across five Western European countries.

AIMS: To assess persistence and adherence to non-vitamin K antagonist oral anticoagulant (NOAC) treatment in patients with atrial fibrillation (AF) in five Western European healthcare settings. METHODS AND RESULTS: We conducted a multi-country observational cohort study, including 559 445 AF patients initiating NOAC therapy from Stockholm (Sweden), Denmark, Scotland, Norway, and Germany between 2011 and 2018. Patients were followed from their first prescription until they switched to a vitamin K antagonist, emigrated, died, or the end of follow-up. We measured persistence and adherence over time and defined adequate adherence as medication possession rate ≥90% among persistent patients only. RESULTS: Overall, persistence declined to 82% after 1 year and to 63% after 5 years. When including restarters of NOAC treatment, 85% of the patients were treated with NOACs after 5 years. The proportion of patients with adequate adherence remained above 80% throughout follow-up. Persistence and adherence were similar between countries and was higher in patients starting treatment in later years. Both first year persistence and adherence were lower with dabigatran (persistence: 77%, adherence: 65%) compared with apixaban (86% and 75%) and rivaroxaban (83% and 75%) and were statistically lower after adjusting for patient characteristics. Adherence and persistence with dabigatran remained lower throughout follow-up. CONCLUSION: Persistence and adherence were high among NOAC users in five Western European healthcare settings and increased in later years. Dabigatran use was associated with slightly lower persistence and adherence compared with apixaban and rivaroxaban.

Trends in Incidence of Intracerebral Hemorrhage and Association With Antithrombotic Drug Use in Denmark, 2005-2018.

Importance: Spontaneous (nontraumatic) intracerebral hemorrhage (ICH) is the most severe complication of antithrombotic drug use. Objectives: To estimate the strength of association between use of antithrombotic drugs and risk of ICH and to examine major changes in the incidence of ICH in the general population. Design, Setting, and Participants: This case-control study of patients with a first-ever ICH from January 1, 2005, to December 31, 2018, matched by age, sex, and calendar year with general population controls (1:40 ratio), assessed case and control patients 20 to 99 years of age in population-based nationwide registries in Denmark (population of 5.8 million). Exposures: Use of low-dose aspirin, clopidogrel, a vitamin K antagonist (VKA), or a direct oral anticoagulant (DOAC). Main Outcomes and Measures: Association of ICH with antithrombotic drug use, annual age- and sex-standardized incidence rate of ICH, and prevalence of treatment with antithrombotic drugs. Conditional logistic regression models estimated adjusted odds ratios (aORs) (95% CIs) for the association of antithrombotic drugs with ICH. Results: Among 16 765 cases with ICH (mean [SD] age, 72.8 [13.1] years; 8761 [52.3%] male), 7473 (44.6%) were exposed to antithrombotic medications at the time of ICH onset. The association with ICH was weakest for current use of low-dose aspirin (cases: 28.7%, controls: 22.6%; aOR, 1.51; 95% CI, 1.44-1.59) and clopidogrel (cases: 6.2%, controls: 3.4%; aOR, 1.65; 95% CI, 1.47-1.84) and strongest with current use of a VKA (cases: 12.0%, controls: 5.0%; aOR, 2.76; 95% CI, 2.58-2.96). The association with ICH was weaker for DOACs (cases: 3.0%, controls: 1.8%; aOR, 1.83; 95% CI, 1.61-2.07) than for VKAs. Compared with 2005, the prevalence of use of oral anticoagulants among general population controls in 2018 was higher (3.8% vs 11.1%), predominantly because of increased use of DOACs (DOACs: 0% vs 7.0%; VKA: 3.8% vs 4.2%). Antiplatelet drugs were used less frequently (24.7% vs 21.4%) because of decreased use of low-dose aspirin (24.3% vs 15.3%), whereas clopidogrel use increased (1.0% vs 6.8%). The age- and sex-standardized incidence rate of ICH decreased from 33 per 100 000 person-years in 2005 to 24 per 100 000 person-years in 2018 (P < .001 for trend). Conclusions and Relevance: In Denmark from 2005 to 2018, use of antithrombotic drugs, especially VKAs, was associated with ICH. Although use of oral anticoagulation increased substantially during the study period, the incidence rate of ICH decreased.

Drug-drug interactions between vitamin K antagonists and statins: a systematic review.

PURPOSE: Concomitant use of vitamin K antagonists (VKA) and statins is frequent in cardiovascular patients. However, clinical guidelines on this drug combination are divergent. Therefore, we performed a systematic review to evaluate the effect of statin initiation on coagulation among VKA users. METHODS: Following the PRISMA guidelines, we applied two broad search strategies for the drug interaction between VKA and statins in both Embase and Pubmed; 8623 unique hits were obtained. In the final sample, eight studies were included. RESULTS: The most frequently used VKA in the studies was warfarin, while simvastatin was the most commonly initiated statin. All included studies showed a minor increase in the anticoagulant effect of VKA following statin initiation during VKA treatment. The reported increases in mean international normalized ratio (INR) ranged from 0.15-0.65. CONCLUSION: The anticoagulant effect of statin initiation in patients treated with VKA is likely to be of limited clinical relevance but should be evaluated individually.

Heparin-induced thrombocytopenia: pathophysiology, diagnosis and treatment.

Introduction: Immune-mediated heparin-induced thrombocytopenia (HIT) is an infrequent complication following heparin exposure but with potentially fatal outcome due to thrombotic complications. Prompt suspension of heparin is necessary if HIT is suspected, followed by initiation of non-heparin anticoagulant therapy.Areas covered: In this review, the pathophysiology and challenges in diagnosing HIT are elucidated. Current and emerging treatment options are discussed with special focus on parenteral thrombin inhibitors (argatroban, bivalirudin), parenteral factor Xa inhibitors (danaparoid, fondaparinux) and direct oral anticoagulants (DOACs [rivaroxaban, apixaban, dabigatran]) including dosing strategies for DOACs. The database PubMed was employed without time boundaries.Expert opinion: Only argatroban holds regulatory approval for HIT treatment in both U.S. and Europe. This treatment is, however, challenged by the need for close monitoring and high costs. Fondaparinux has been increasingly used for off-label treatment and during recent years, evidence for the use of DOACs has emerged. Preliminary results from observational studies hold promise for future use of DOACs in the acute and subacute phase of HIT. However, so far, the use of DOACs in acute HIT should be reserved for clinically stable patients without severe thrombotic complications. Importantly, both fondaparinux and DOAC use is contraindicated in severe renal insufficiency.

Venous Thromboembolism and Major Bleeding in Patients With Coronavirus Disease 2019 (COVID-19): A Nationwide, Population-Based Cohort Study.

BACKGROUND: Venous thromboembolism (VTE) is a potentially fatal complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and thromboprophylaxis should be balanced against risk of bleeding. This study examined risks of VTE and major bleeding in hospitalized and community-managed SARS-CoV-2 patients compared with control populations. METHODS: Using nationwide population-based registries, 30-day risks of VTE and major bleeding in SARS-CoV-2 positive patients were compared with those of SARS-CoV-2 test-negative patients and with an external cohort of influenza patients. Medical records of all COVID-19 patients at 6 departments of infectious diseases in Denmark were reviewed in detail. RESULTS: The overall 30-day risk of VTE was 0.4% (40/9460) among SARS-CoV-2 patients (16% hospitalized), 0.3% (649/226 510) among SARS-CoV-2 negative subjects (12% hospitalized), and 1.0% (158/16 281) among influenza patients (59% hospitalized). VTE risks were higher and comparable in hospitalized SARS-CoV-2 positive (1.5%), SARS-CoV-2 negative (1.8%), and influenza patients (1.5%). Diagnosis of major bleeding was registered in 0.5% (47/9460) of all SARS-CoV-2 positive individuals and in 2.3% of those hospitalized. Medical record review of 582 hospitalized SARS-CoV-2 patients observed VTE in 4% (19/450) and major bleeding in 0.4% (2/450) of ward patients, of whom 31% received thromboprophylaxis. Among intensive care patients (100% received thromboprophylaxis), risks were 7% (9/132) for VTE and 11% (15/132) for major bleeding. CONCLUSIONS: Among people with SARS-CoV-2 infection in a population-based setting, VTE risks were low to moderate and were not substantially increased compared with SARS-CoV-2 test-negative and influenza patients. Risk of severe bleeding was low for ward patients, but mirrored VTE risk in the intensive care setting.

Use of dipeptidyl peptidase-4 inhibitors and risk of splanchnic vein thrombosis: A Danish nationwide new-user active comparator cohort study.

Use of dipeptidyl peptidase-4 (DPP-4) inhibitors, on the basis of spontaneous adverse event reports, has recently been suspected of causing splanchnic vein thrombosis. Here, we report the results of a population-based new-user active comparator cohort study addressing this hypothesis, comparing DPP-4 inhibitor initiators (n = 75 042) with initiators of glucagon-like-peptide-1 receptor agonists (GLP-1RAs) or sodium-glucose co-transporter-2 (SGLT2) inhibitors (n = 38 718). We estimated the hazard ratio (HR) associating DPP-4 inhibitor use with risk of splanchnic vein thrombosis using Cox regression. In a crude analysis, the incidence rate of splanchnic vein thrombosis was 0.22/1000 person-years among DPP-4 inhibitor initiators, compared to 0.17 among GLP-1RA/SGLT2 inhibitor initiators, corresponding to an unadjusted absolute incidence rate difference of 0.05 (95% confidence interval [CI] -0.04 to 0.14) and an HR of 1.29 (95% CI 0.78 to 2.15). Adjusting for potential confounders using stabilized inverse probability of treatment weighing, we obtained an absolute incidence rate difference of 0.03/1000 person-years (95% CI -0.07 to 0.14) and an HR of 1.18 (95% CI 0.62 to 2.26). No evidence of increased risk of splanchnic vein thrombosis was found in supplementary analyses, including an absence of any dose-response patterns. As such, we found no association between DPP-4 inhibitor use and splanchnic vein thrombosis risk.

Real-world experience with reversal of dabigatran by idarucizumab.

AIMS: Idarucizumab reverses the anticoagulant effect of dabigatran. We aimed to investigate real-world experience with idarucizumab and associated clinical outcomes. METHODS: We conducted a retrospective observational case series on dabigatran users treated with idarucizumab. Using electronic patient records, we identified patients from December 2015 (market introduction) to 31 December 2019 from the Central Denmark Region, covering approximately 1.3 million inhabitants. Treatment indications included need of acute surgery, major bleeding, dabigatran intoxication and need of thrombolysis. Outcomes were defined according to treatment indication, and adverse events were defined as bleeding, thrombosis or death within 30 days of infusion. RESULTS: A total of 46 dabigatran users were treated with idarucizumab. All patients except one received dabigatran due to atrial fibrillation. Indications for idarucizumab use were need of acute surgery in 22 (48%), severe bleeding in 20 (43%), dabigatran intoxication in three (7%), and prior to thrombolysis in acute stroke in one (2%) patient. There were no reports of excessive bleeding during surgery in patients reversed just prior to surgery. For patients presenting with severe bleeding, all but one achieved effective haemostasis. Among all patients receiving idarucizumab, six (13%) experienced bleeding within 30 days after infusion. None experienced thromboembolic complications. At 30 days follow-up, 38 (83%) patients were alive of whom 35 (92%) had restarted anticoagulant treatment. CONCLUSION: This study of real-world application of idarucizumab demonstrated effectiveness in terms of surgery performed without excessive bleeding and cessation of severe bleeding in dabigatran-treated patients. Safety appeared high as no patients experienced thromboembolic complications within 30 days.

Antimycotic Treatment of Oral Candidiasis in Warfarin Users.

PURPOSE: Azole antimycotics and nystatin oral solution are used to treat oral candidiasis. Azoles inhibit cytochrome (CYP) P450-dependent metabolism of warfarin, which could increase the anticoagulant effect of warfarin. Nystatin is not expected to interfere with warfarin metabolism, but current data are conflicting. With this study, we aimed to explore the potential drug-drug interactions between warfarin and azole antimycotics used in the treatment of oral candidiasis, that is, systemic fluconazole, miconazole oral gel, and nystatin oral solution. METHODS: By linking clinical data on international normalized ratio (INR) measurements with administrative data on filled prescriptions of warfarin and antimycotics during 2000-2015, we explored INR changes in warfarin users relative to initiation of systemic fluconazole (n = 413), miconazole oral gel (n = 330), and nystatin oral solution (n = 399). RESULTS: We found a significant increase in mean INR of 0.83 (95% confidence interval [CI] 0.61-1.04) and 1.27 (95% CI 0.94-1.59) following initiation of systemic fluconazole and miconazole oral gel, respectively. Also, the proportion of patients experiencing an INR-value above 5 was increased after initiation of fluconazole (from 4.3% to 15.3%) and miconazole (from 5.5% to 30.1%). INR was unaffected by initiation of nystatin oral solution (mean change 0.08; 95% CI -0.10 to 0.25). CONCLUSION: Initiation of systemic fluconazole and miconazole oral gel was associated with increased INR in warfarin users. A similar association was not found for nystatin oral solution, which thus appears to be the safest alternative when treating oral candidiasis in warfarin users.

[Menorrhagia during oral anticoagulant therapy].

Menorrhagia is a common complication to oral anticoagulant therapy in premenopausal women. Clinical management of menorrhagia poses a clinical dilemma with the need of weighting bleeding risk against the risk of recurrent thrombosis. In this review, we describe the risk of menorrhagia during oral anticoagulant therapy, with emphasis on the differences between the specific anticoagulant drugs. We critically assess the treatment options for anticoagulant-associated menorrhagia, and we provide a treatment algorithm for the management of anticoagulant-associated menorrhagia.

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.

[Venous thromboembolism in patients with COVID-19].

The importance of venous thromboembolism (VTE) as a major complication in patients with severe corona virus disease 2019 (COVID-19) is becoming increasingly evident. In this review, we describe the proposed pathophysiology of the prothrombotic coagulation changes observed in patients with COVID-19. Further, based on a review of the currently available evidence on VTE prevalence in patients with COVID-19, we present and discuss the recommendations from the Danish Society of Thrombosis and Haemostasis on the use of thromboprophylaxis in patients with COVID-19.

[Severe dabigatran intoxication complicated by insufficient reversal by idarucizumab].

Despite the emergence of the specific dabigatran antidote idarucizumab, reversal of dabigatran in the context of severe intoxication remains a clinical challenge. We report a case of severe intoxication secondary to acute renal failure in a 65-year-old man with atrial fibrillation. Idarucizumab was administered repeatedly but failed to reverse the effect of dabigatran, most likely due to ongoing redistribution. Full reversal of dabigatran was obtained through continuous haemodialysis over days. Further, secondary to the intoxication, the patient developed parenchymatous acute liver injury.