Antibody levels to SARS-CoV-2 spike protein in mothers and children from delivery to six months later.

INTRODUCTION: Pregnant women are vulnerable to severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection. Neutralizing antibodies against the SARS-CoV-2 spike (S) protein protect from severe disease. This study analyzes the antibody titers to SARS-CoV-2 S protein in pregnant women and their newborns at delivery, and six months later. METHODS: We conducted a prospective study on pregnant women with confirmed SARS-CoV-2 infection and newborns. Antibody (IgG, IgM, and IgA) titers were determined using immunoassays in serum and milk samples. An angiotensin-converting enzyme 2 (ACE2) receptor-binding inhibition assay to the S protein was performed on the same serum and milk samples. RESULTS: At birth, antibodies to SARS-CoV-2 spike protein were detected in 81.9% of mothers' sera, 78.9% of cord blood samples, and 63.2% of milk samples. Symptomatic women had higher antibody titers (IgG, IgM, and IgA) than the asymptomatic ones (P < 0.05). At six months postpartum, IgG levels decreased drastically in children's serum (P < 0.001) but remained high in mothers' serum. Antibody titers correlated positively with its capacity to inhibit the ACE2-spike protein interaction at baseline in maternal sera (R2  = 0.203; P < 0.001), cord sera (R2  = 0.378; P < 0.001), and milk (R2  = 0.564; P < 0.001), and at six months in maternal sera (R2  = 0.600; P < 0.001). CONCLUSIONS: High antibody levels against SARS-CoV-2 spike protein were found in most pregnant women. Due to the efficient transfer of IgG to cord blood and high IgA titers in breast milk, neonates may be passively immunized to SARS-CoV-2 infection. Our findings could guide newborn management and maternal vaccination policies.

NFKB2 haploinsufficiency identified via screening for IFN-α2 autoantibodies in children and adolescents hospitalized with SARS-CoV-2-related complications.

BACKGROUND: Autoantibodies against type I IFNs occur in approximately 10% of adults with life-threatening coronavirus disease 2019 (COVID-19). The frequency of anti-IFN autoantibodies in children with severe sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is unknown. OBJECTIVE: We quantified anti-type I IFN autoantibodies in a multicenter cohort of children with severe COVID-19, multisystem inflammatory syndrome in children (MIS-C), and mild SARS-CoV-2 infections. METHODS: Circulating anti-IFN-α2 antibodies were measured by a radioligand binding assay. Whole-exome sequencing, RNA sequencing, and functional studies of peripheral blood mononuclear cells were used to study any patients with levels of anti-IFN-α2 autoantibodies exceeding the assay's positive control. RESULTS: Among 168 patients with severe COVID-19, 199 with MIS-C, and 45 with mild SARS-CoV-2 infections, only 1 had high levels of anti-IFN-α2 antibodies. Anti-IFN-α2 autoantibodies were not detected in patients treated with intravenous immunoglobulin before sample collection. Whole-exome sequencing identified a missense variant in the ankyrin domain of NFKB2, encoding the p100 subunit of nuclear factor kappa-light-chain enhancer of activated B cells, aka NF-κB, essential for noncanonical NF-κB signaling. The patient's peripheral blood mononuclear cells exhibited impaired cleavage of p100 characteristic of NFKB2 haploinsufficiency, an inborn error of immunity with a high prevalence of autoimmunity. CONCLUSIONS: High levels of anti-IFN-α2 autoantibodies in children and adolescents with MIS-C, severe COVID-19, and mild SARS-CoV-2 infections are rare but can occur in patients with inborn errors of immunity.

Vaccine breakthrough hypoxemic COVID-19 pneumonia in patients with auto-Abs neutralizing type I IFNs.

Life-threatening 'breakthrough' cases of critical COVID-19 are attributed to poor or waning antibody response to the SARS-CoV-2 vaccine in individuals already at risk. Pre-existing autoantibodies (auto-Abs) neutralizing type I IFNs underlie at least 15% of critical COVID-19 pneumonia cases in unvaccinated individuals; however, their contribution to hypoxemic breakthrough cases in vaccinated people remains unknown. Here, we studied a cohort of 48 individuals (age 20-86 years) who received 2 doses of an mRNA vaccine and developed a breakthrough infection with hypoxemic COVID-19 pneumonia 2 weeks to 4 months later. Antibody levels to the vaccine, neutralization of the virus, and auto-Abs to type I IFNs were measured in the plasma. Forty-two individuals had no known deficiency of B cell immunity and a normal antibody response to the vaccine. Among them, ten (24%) had auto-Abs neutralizing type I IFNs (aged 43-86 years). Eight of these ten patients had auto-Abs neutralizing both IFN-α2 and IFN-ω, while two neutralized IFN-ω only. No patient neutralized IFN-ß. Seven neutralized 10 ng/mL of type I IFNs, and three 100 pg/mL only. Seven patients neutralized SARS-CoV-2 D614G and the Delta variant (B.1.617.2) efficiently, while one patient neutralized Delta slightly less efficiently. Two of the three patients neutralizing only 100 pg/mL of type I IFNs neutralized both D61G and Delta less efficiently. Despite two mRNA vaccine inoculations and the presence of circulating antibodies capable of neutralizing SARS-CoV-2, auto-Abs neutralizing type I IFNs may underlie a significant proportion of hypoxemic COVID-19 pneumonia cases, highlighting the importance of this particularly vulnerable population.

C-reactive protein isoforms as prognostic markers of COVID-19 severity.

C-reactive protein (CRP), an active regulator of the innate immune system, has been related to COVID-19 severity. CRP is a dynamic protein undergoing conformational changes upon activation in inflammatory microenvironments between pentameric and monomeric isoforms. Although pentameric CRP is the circulating isoform routinely tested for clinical purposes, monomeric CRP shows more proinflammatory properties. Therefore, we aimed to determine the potential of monomeric CRP in serum as a biomarker of disease severity in COVID-19 patients (admission to intensive care unit [ICU] and/or in-hospital mortality). We retrospectively determined clinical and biological features as well as pentameric and monomeric CRP levels in a cohort of 97 COVID-19 patients within 72h of hospital admission. Patients with severe disease had higher levels of both pentameric and monomeric CRP. However, multivariate analysis showed increased mCRP but not pCRP to be independently associated to disease severity. Notably, mCRP levels higher than 4000 ng/mL (OR: 4.551, 95% CI: 1.329-15.58), together with number of co-morbidities, low lymphocyte count, and procalcitonin levels were independent predictors of disease severity in the multivariate model. Our results show the potential of mCRP levels as a marker of clinical severity in COVID-19 disease.

C-reactive protein isoforms as prognostic markers of COVID-19 severity

C-reactive protein (CRP), an active regulator of the innate immune system, has been related to COVID-19 severity. CRP is a dynamic protein undergoing conformational changes upon activation in inflammatory microenvironments between pentameric and monomeric isoforms. Although pentameric CRP is the circulating isoform routinely tested for clinical purposes, monomeric CRP shows more proinflammatory properties. Therefore, we aimed to determine the potential of monomeric CRP in serum as a biomarker of disease severity in COVID-19 patients (admission to intensive care unit [ICU] and/or in-hospital mortality). We retrospectively determined clinical and biological features as well as pentameric and monomeric CRP levels in a cohort of 97 COVID-19 patients within 72h of hospital admission. Patients with severe disease had higher levels of both pentameric and monomeric CRP. However, multivariate analysis showed increased mCRP but not pCRP to be independently associated to disease severity. Notably, mCRP levels higher than 4000 ng/mL (OR: 4.551, 95% CI: 1.329-15.58), together with number of co-morbidities, low lymphocyte count, and procalcitonin levels were independent predictors of disease severity in the multivariate model. Our results show the potential of mCRP levels as a marker of clinical severity in COVID-19 disease.

Autoantibody discovery across monogenic, acquired, and COVID-19-associated autoimmunity with scalable PhIP-seq.

Phage immunoprecipitation sequencing (PhIP-seq) allows for unbiased, proteome-wide autoantibody discovery across a variety of disease settings, with identification of disease-specific autoantigens providing new insight into previously poorly understood forms of immune dysregulation. Despite several successful implementations of PhIP-seq for autoantigen discovery, including our previous work (Vazquez et al., 2020), current protocols are inherently difficult to scale to accommodate large cohorts of cases and importantly, healthy controls. Here, we develop and validate a high throughput extension of PhIP-seq in various etiologies of autoimmune and inflammatory diseases, including APS1, IPEX, RAG1/2 deficiency, Kawasaki disease (KD), multisystem inflammatory syndrome in children (MIS-C), and finally, mild and severe forms of COVID-19. We demonstrate that these scaled datasets enable machine-learning approaches that result in robust prediction of disease status, as well as the ability to detect both known and novel autoantigens, such as prodynorphin (PDYN) in APS1 patients, and intestinally expressed proteins BEST4 and BTNL8 in IPEX patients. Remarkably, BEST4 antibodies were also found in two patients with RAG1/2 deficiency, one of whom had very early onset IBD. Scaled PhIP-seq examination of both MIS-C and KD demonstrated rare, overlapping antigens, including CGNL1, as well as several strongly enriched putative pneumonia-associated antigens in severe COVID-19, including the endosomal protein EEA1. Together, scaled PhIP-seq provides a valuable tool for broadly assessing both rare and common autoantigen overlap between autoimmune diseases of varying origins and etiologies.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Transmission Dynamics and Immune Responses in a Household of Vaccinated Persons.

While SARS-CoV-2 vaccines prevent severe disease effectively, postvaccination "breakthrough" COVID-19 infections and transmission among vaccinated individuals remain ongoing concerns. We present an in-depth characterization of transmission and immunity among vaccinated individuals in a household, revealing complex dynamics and unappreciated comorbidities, including autoimmunity to type 1 interferon in the presumptive index case.

SARS-CoV2 Infection During Pregnancy Causes Persistent Immune Abnormalities in Women Without Affecting the Newborns.

SARS-CoV2 infection in pregnancy and exposed newborns is poorly known. We performed a longitudinal analysis of immune system and determined soluble cytokine levels in pregnant women infected with SARS-CoV2 and in their newborns. Women with confirmed SARS-CoV2 infection and their exposed uninfected newborns were recruited from Hospital General Universitario Gregorio Marañón. Peripheral blood mononuclear cells (PBMCs), cord cells and plasma were collected at birth and 6 months later. Immunophenotyping of natural killer (NK), monocytes and CD4/CD8 T-cells were studied in cryopreserved PBMCs and cord cells by multiparametric flow cytometry. Up to 4 soluble pro/anti-inflammatory cytokines were assessed in plasma/cord plasma by ELISA assay. SARS-CoV2-infected mothers and their newborns were compared to matched healthy non-SARS-CoV2-infected mothers and their newborns. The TNFα and IL-10 levels of infected mothers were higher at baseline than those of healthy controls. Infected mothers showed increased NK cells activation and reduced expression of maturation markers that reverted after 6 months. They also had high levels of Central Memory and low Effector Memory CD4-T cell subsets. Additionally, the increased CD4- and CD8-T cell activation (CD154 and CD38) and exhaustion (TIM3/TIGIT) levels at baseline compared to controls remained elevated after 6 months. Regarding Treg cells, the levels were lower at infected mothers at baseline but reverted after 6 months. No newborn was infected at birth. The lower levels of monocytes, NK and CD4-T cells observed at SARS-CoV2-exposed newborns compared to unexposed controls significantly increased 6 months later. In conclusion, SARS-CoV2 infection during pregnancy shows differences in immunological components that could lead newborns to future clinical implications after birth. However, SARS-CoV2 exposed 6-months-old newborns showed no immune misbalance, whereas the infected mothers maintain increased activation and exhaustion levels in T-cells after 6 months.

Vaccine breakthrough hypoxemic COVID-19 pneumonia in patients with auto-Abs neutralizing type I IFNs

Life-threatening ‘breakthrough’ cases of critical COVID-19 are attributed to poor or waning antibody response to the SARS-CoV-2 vaccine in individuals already at risk. Pre-existing autoantibodies (auto-Abs) neutralizing type I IFNs underlie at least 15% of critical COVID-19 pneumonia cases in unvaccinated individuals;however, their contribution to hypoxemic breakthrough cases in vaccinated people remains unknown. Here, we studied a cohort of 48 individuals (age 20-86 years) who received 2 doses of an mRNA vaccine and developed a breakthrough infection with hypoxemic COVID-19 pneumonia 2 weeks to 4 months later. Antibody levels to the vaccine, neutralization of the virus, and auto-Abs to type I IFNs were measured in the plasma. Forty-two individuals had no known deficiency of B cell immunity and a normal antibody response to the vaccine. Among them, ten (24%) had auto-Abs neutralizing type I IFNs (aged 43-86 years). Eight of these ten patients had auto-Abs neutralizing both IFN-α2 and IFN-ω, while two neutralized IFN-ω only. No patient neutralized IFN-β. Seven neutralized 10 ng/mL of type I IFNs, and three 100 pg/mL only. Seven patients neutralized SARS-CoV-2 D614G and the Delta variant (B.1.617.2) efficiently, while one patient neutralized Delta slightly less efficiently. Two of the three patients neutralizing only 100 pg/mL of type I IFNs neutralized both D61G and Delta less efficiently. Despite two mRNA vaccine inoculations and the presence of circulating antibodies capable of neutralizing SARS-CoV-2, auto-Abs neutralizing type I IFNs may underlie a significant proportion of hypoxemic COVID-19 pneumonia cases, highlighting the importance of this particularly vulnerable population. Type I IFN auto-Abs are found in 20% of hypoxemic, mRNA vaccinated COVID-19 patients despite SARS-CoV-2 neutralizing antibodies. Description

Impact of Gestational COVID-19 on Neonatal Outcomes: Is Vertical Infection Possible?

BACKGROUND: The vertical transmission of severe acute respiratory coronavirus-2 (SARS-CoV-2) remains highly debated. Here, we evaluated SARS-CoV-2-transmission in newborns with intrauterine conditions. METHODS: This was a prospective, observational and multicentric study involving 13 Spanish hospitals included in the GEStational and NEOnatal-COVID cohort. Pregnant women with microbiologically confirmed SARS-CoV-2 infection during any trimester of pregnancy or delivery and their newborns were included from March to November 2020. Demographic, clinical and microbiological data were also obtained. Viral loads were analyzed in different maternal and newborn biological samples (placenta, breast milk and maternal blood; urine, meconium and newborn blood). RESULTS: A total of 177 newborns exposed to SARS-CoV-2 were included. Newborns were tested by reverse transcriptase-polymerase chain reaction using nasopharyngeal swabs within the first 24-48 hours of life and at 14 days of life. In total 5.1% were considered to have SARS-CoV-2 infection in the neonatal period, with 1.7% considered intrauterine and 3.4% intrapartum or early postnatal transmission cases. There were no differences in the demographic and clinical characteristics of the pregnant women and their newborns' susceptibility to infections in their perinatal history or background. CONCLUSIONS: Intrauterine transmission of SARS-CoV-2 is possible, although rare, with early postnatal transmission occurring more frequently. Most infected newborns remained asymptomatic or had mild symptoms that evolved well during follow-up. We did not find any maternal characteristics predisposing infants to neonatal infection. All infected newborn mothers had acute infection at delivery.Although there was no presence of SARS-CoV2 in cord blood or breast milk samples, SARS-CoV-2 viral load was detected in urine and meconium samples from infected newborns.

Type I interferon autoantibodies are associated with systemic immune alterations in patients with COVID-19.

Neutralizing autoantibodies against type I interferons (IFNs) have been found in some patients with critical coronavirus disease 2019 (COVID-19), the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the prevalence of these antibodies, their longitudinal dynamics across the disease severity scale, and their functional effects on circulating leukocytes remain unknown. Here, in 284 patients with COVID-19, we found type I IFN­specific autoantibodies in peripheral blood samples from 19% of patients with critical disease and 6% of patients with severe disease. We found no type I IFN autoantibodies in individuals with moderate disease. Longitudinal profiling of over 600,000 peripheral blood mononuclear cells using multiplexed single-cell epitope and transcriptome sequencing from 54 patients with COVID-19 and 26 non­COVID-19 controls revealed a lack of type I IFN­stimulated gene (ISG-I) responses in myeloid cells from patients with critical disease. This was especially evident in dendritic cell populations isolated from patients with critical disease producing type I IFN­specific autoantibodies. Moreover, we found elevated expression of the inhibitory receptor leukocyte-associated immunoglobulin-like receptor 1 (LAIR1) on the surface of monocytes isolated from patients with critical disease early in the disease course. LAIR1 expression is inversely correlated with ISG-I expression response in patients with COVID-19 but is not expressed in healthy controls. The deficient ISG-I response observed in patients with critical COVID-19 with and without type I IFN­specific autoantibodies supports a unifying model for disease pathogenesis involving ISG-I suppression through convergent mechanisms.

SARS-COV-2 infection in pregnant women and newborns in a Spanish cohort (GESNEO-COVID) during the first wave.

BACKGROUND: Knowledge about SARS-CoV-2 infection in pregnancy and newborns is scarce. The objective of this study is to analyse clinical and epidemiological characteristics of a cohort of women infected with SARS-CoV-2 during pregnancy and their newborns exposed to SARS-CoV-2 during gestation. METHODS: Multicentric observational study of Spanish hospitals from the GESNEO-COVD cohort, participants in RECLIP (Spanish Network of Paediatric Clinical Assays). Women with confirmed SARS-CoV-2 infection by PCR and/or serology during pregnancy, diagnosed and delivering during the period 15/03/2020-31/07/2020 were included. Epidemiological, clinical, and analytical data was collected. RESULTS: A total of 105 pregnant women with a median of 34.1 years old (IQR: 28.8-37.1) and 107 newborns were included. Globally, almost 65% of pregnant women had some COVID-19 symptoms and more than 43% were treated for SARS-COV-2. Overall, 30.8% of pregnant women had pneumonia and 5 (4.8%) women were admitted to the intensive care unit needing invasive mechanical ventilation. There was a rate of 36.2% of caesarean sections, which was associated with pneumonia during pregnancy (OR: 4.203, CI 95%: 1.473-11.995) and lower gestational age at delivery (OR: 0.724, CI 95%: 0.578-0.906). The prevalence of preterm birth was 20.6% and prematurity was associated with pneumonia during gestation (OR: 6.970, CI95%: 2.340-22.750) and having a positive SARS-CoV-2 PCR at delivery (OR: 6.520, CI95%: 1.840-31.790). All nasopharyngeal PCR in newborns were negative at birth and one positivized at 15 days of life. Two newborns died, one due to causes related to prematurity and another of unexpected sudden death during early skin-to-skin contact after delivery. CONCLUSIONS: Although vertical transmission has not been reported in this cohort, the prognosis of newborns could be worsened by SARS-CoV-2 infection during pregnancy as COVID-19 pneumonia increased the risk of caesarean section deliveries and preterm births.

Epidemiology, management and risk of SARS-CoV-2 transmission in a cohort of newborns born to mothers diagnosed with COVID-19 infection.

INTRODUCTION: The impact of maternal SARS-CoV-2 infection and its risk of vertical transmission is still not well known. Recommendations from scientific societies seek to provide safety for newborns without compromising the benefits of early contact. The aim of the study is to describe characteristics and evolution of newborns born to mothers with SARS-CoV-2 infection, as well as the implemented measures following recommendations from the Sociedad Española de Neonatología. METHODS: Observational, prospective and single-center cohort study. A specific circuit was designed for mothers with SARS-CoV-2 infection and their newborns. Epidemiological and clinical data were collected. PCR were performed in newborns at delivery and at 14 days of age. RESULTS: 73 mothers and 75 newborns were included in the study. 95.9% of maternal infections were diagnosed during the third trimester of pregnancy, 43.8% were asymptomatic. Median gestational age was 38 weeks (IQR: 37-40), 25.9% of newborns required admission to Neonatology. Skin-to-skin mother care was performed in 68% of newborns, 80% received exclusive maternal or donated breast milk during hospital stay. No positive PCR results were observed in newborns at delivery, one case of positive PCR was observed in an asymptomatic neonate at 14 days of age. CONCLUSIONS: Risk of SARS-CoV-2 transmission is low when complying to the recommendations issued by Sociedad Española de Neonatología, allowing rooming-in and promoting breastfeeding.

INTRODUCCIÓN: La repercusión de la infección materna por SARS-Cov-2 y su riesgo de transmisión vertical es aún poco conocido. Las recomendaciones de las sociedades científicas buscan proporcionar seguridad para el recién nacido sin comprometer los beneficios del contacto precoz. El objetivo del estudio es describir las características y evolución de recién nacidos de madres infectadas por SARS-CoV2, así como las medidas implementadas siguiendo las recomendaciones de la Sociedad Española de Neonatología. MATERIAL Y MÉTODOS: Estudio observacional, prospectivo y unicentro de cohortes. Se diseñó un circuito específico para madres con infección por SARS-CoV2 y sus hijos. Se recogieron datos epidemiológicos y clínicos de las madres y sus recién nacidos. Se realizó PCR al nacer y a los 14 días. RESULTADOS: Se incluyeron 73 madres y 75 neonatos. El 95.9% de infecciones maternas fueron diagnosticadas durante el tercer trimestre, el 43.8% fueron asintomáticas. La mediana de edad gestacional fue 38 semanas (RIC:37­40), el 25.9% de los neonatos requirió ingreso. En el 68% se realizó contacto piel con piel en paritorio y el 80% recibieron lactancia materna o donada exclusiva durante su estancia. No se objetivaron resultados positivos de PCR en la primera muestra obtenida nada más nacer, se objetivó 1 caso de PCR positiva en un neonato asintomático a los 14 días. CONCLUSIONES: El riesgo de transmisión de la infección por SARS-CoV2 es bajo cumpliendo los protocolos de la Sociedad Española de Neonatología, permitiendo el alojamiento conjunto de madre e hijo, el contacto precoz y el establecimiento eficaz de la lactancia materna.

[Epidemiology, management and risk of SARS-CoV-2 transmission in a cohort of newborns born to mothers diagnosed with COVID-19 infection]. / Epidemiología, manejo y riesgo de transmisión de SARS-CoV-2 en una cohorte de hijos de madres afectas de COVID-19.

INTRODUCTION: The impact of maternal SARS-CoV-2 infection and its risk of vertical transmission is still not well known. Recommendations from scientific societies seek to provide safety for newborns without compromising the benefits of early contact. The aim of the study is to describe characteristics and evolution of newborns born to mothers with SARS-CoV-2 infection, as well as the implemented measures following recommendations from the Sociedad Española de Neonatología. METHODS: Observational, prospective and single-center cohort study. A specific circuit was designed for mothers with SARS-CoV-2 infection and their newborns. Epidemiological and clinical data were collected. PCR were performed in newborns at delivery and at 14 days of age. RESULTS: 73 mothers and 75 newborns were included in the study. 95.9% of maternal infections were diagnosed during the third trimester of pregnancy, 43.8% were asymptomatic. Median gestational age was 38 weeks (IQR: 37-40), 25.9% of newborns required admission to Neonatology. Skin-to-skin mother care was performed in 68% of newborns, 80% received exclusive maternal or donated breast milk during hospital stay. No positive PCR results were observed in newborns at delivery, one case of positive PCR was observed in an asymptomatic neonate at 14 days of age. CONCLUSIONS: Risk of SARS-CoV-2 transmission is low when complying to the recommendations issued by Sociedad Española de Neonatología, allowing rooming-in and promoting breastfeeding.

Drug-drug interactions with direct oral anticoagulants associated with adverse events in the real world: A systematic review.

BACKGROUND: Direct oral anticoagulants (DOACs) have emerged as safe and effective alternatives to Vitamin-K antagonists for treatment and prevention of arterial and venous thrombosis. Due to their novelty, pharmacokinetic DOAC drug-drug interactions (DDIs) that result in clinical adverse events have not been well-documented. OBJECTIVE: This study aims to systematically review reported pharmacokinetic DDIs resulting in clinical adverse events through documented observational evidence to better inform clinicians in clinical practice. METHODS: A comprehensive literature review of EMBASE, MEDLINE, and Ovid HealthStar was conducted through March 10th, 2020. Two independent reviewers screened and extracted data from eligible articles according to pre-established inclusion and exclusion criteria. Articles reporting bleeding or thrombotic outcomes in non-controlled (observational) settings resulting from suggested pharmacokinetic DOAC DDIs were included. RESULTS: A total of 5567 citations were reviewed, of which 24 were included following data extraction. The majority were case reports (n = 21) documenting a single adverse event resulting from a suspected DOAC DDI, while the remaining papers were a case series (n = 1) and cohort studies (n = 2). The most commonly reported interacting drugs were amiodarone and ritonavir (bleeding), and phenobarbital, phenytoin, and carbamazepine (thrombosis). Bleeding events more often resulted from a combined mechanism (P-glycoprotein AND CYP3A4 inhibition), whereas thrombotic events resulted from either combined OR single P-glycoprotein/CYP3A4 induction. CONCLUSION: Current literature evaluating the real-world risk of DOAC DDIs is limited to few case reports and retrospective observational analyses. Clinicians are encouraged to continue to report suspected drug interactions resulting in adverse events.