Safety and Efficacy Outcomes of Home and Hospital Warfarin Management Within a Pediatric Anticoagulation Clinic

Evaluation, analysis, and reporting of medication adherence for clinical trials of anticoagulants in children: guidance from the ISTH SSC Subcommittee on Pediatric and Neonatal Thrombosis and Hemostasis

In response to growing recognition that nonadherence prevents children, adolescents, and young adults from achieving the therapeutic benefits of anticoagulant medication, the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee Subcommittee on Pediatric and Neonatal Thrombosis and Hemostasis convened a working party on medication adherence. The primary aim of this article was to synthesize recommendations from the larger adherence science literature to provide guidance regarding the classification, collection, and interpretation of anticoagulation adherence data. The secondary aim of this article was to evaluate the degree to which trials published from 2013 to 2023 adhered to these guidance recommendations. As less than half of all trials reported on adherence and none included all recommended elements, the proposed International Society on Thrombosis and Haemostasis Scientific and Standardization Committee guidance has the potential to enhance the rigor and reproducibility of pediatric anticoagulant research.

Guiding warfarin self-management in children: development of a warfarin nomogram

Background

Warfarin therapy in children is impacted by many variables. To support the implementation of a self-management program within a pediatric anticoagulation service, a pediatric-specific warfarin nomogram was needed. A literature review revealed no published pediatric nomograms; therefore, a nomogram was developed drawing upon an evidence-based "Warfarin Information for Clinicians" hospital guideline.

Objectives

This study aimed to evaluate the suitability of a pediatric warfarin nomogram.

Methods

A retrospective audit of electronic medical records compared the dosing and international normalized ratio (INR) retest decisions made by hematology clinicians to the dosing and retesting recommended by a new warfarin nomogram at a pediatric hospital. Children (aged 6 months-18 years) receiving warfarin therapy for >6 months were included. Data were collected between September 2019 and February 2020. Descriptive data analysis was performed. The study was approved by the hospital's Human Research Ethics Committee.

Results

Warfarin dosing and INR retest decisions for 39 children were included, equating to 521 INRs. The nomogram matched 81.4% of clinicians dosing decisions and 30% of INR retest decisions. Moreover, 59% of the clinician-recommended retest dates were earlier than the nomogram recommendation. In the INR 2.0-3.0 group, 84.4% of dosing decisions and 72% of retest decisions matched the nomogram.

Conclusions

These results suggest that this pediatric nomogram is a suitable tool for warfarin dosing, as recommended warfarin doses matched the majority of clinicians' decisions. Modification may be needed to nomogram recommendations for the time to retest. This nomogram can be used to support warfarin self-management and may assist clinicians and patients or families in making evidence-based dosing decisions.

A regional anticoagulation program improves safety and outcomes for both children and adults

BACKGROUND

Evidence-based anticoagulation programs usually serve a local, adult patient population. Here we report outcomes for a regional combined pediatric-adult program.

AIMS

The aims of this study were: (1) Compare the pre- vs. post-implementation quality of therapy (% time in therapeutic range (%TTR) and compliance). (2) Assess anticoagulant-relevant outcomes (bleeding and thrombotic complications).

METHODS

Data were collected for the years 2014-2019. Rosendaal linear interpolation was used to calculate %TTR. Bleeding complications were categorized using ISTH-SSC standard nomenclature and new thrombotic events were reviewed.

RESULTS

The patients were divided into a long-term warfarin group (N = 308), 80.2% of whom had cardiac-related therapeutic indications (median age 24y), and a second group (N = 114) comprised of short-term and non-warfarin long-term anticoagulation (median age 16y). Median %TTR for those on long-term warfarin was 78.9%. The incidence of major and clinically relevant non-major bleeding events was 1.65 and 2.43 /100 person-years of warfarin use, respectively. Thromboembolism (TE) incidence was 0.78/100 patient-years of warfarin use. Neither bleeding nor thrombosis was associated with %TTR (p = 0.48). Anticoagulant indication was the only variable associated with bleeding risk (p = 0.005). The second group had no on-therapy TE events but 7.9% experienced bleeding. Complete data were available for a randomly sampled pre-program warfarin group (N = 26). Median %TTR improved from 17.5 to 87% pre- vs. post-implementation. Similarly, compliance (defined as ≥ 1 INR/month) improved by 34.3%.

CONCLUSIONS

In conclusion, this program significantly improved and sustained %TTR and compliance. The lack of association between bleeding and thrombosis events and %TTR may be related to the high median %TTR (> 70%) achieved by this approach.

Using an electronic medical record patient portal for warfarin self-management: Empowering children and parents

Background

Many children taking warfarin perform their international normalized ratio (INR) at home, with results phoned to a clinician who instructs warfarin dosing. Data suggest that parents can be supported to make warfarin dosing decisions themselves, a process known as patient self-management (PSM).

Objectives

This study aimed to determine the suitability and acceptability of warfarin PSM in children using the Epic Patient Portal.

Methods

Children currently performing INR patient self-testing were eligible. Participation involved an individualized education session, adherence to the PSM program, and participation in phone interviews. Clinical outcomes (INR time in therapeutic range and safety outcomes), patient portal functionality, and family experience were assessed. The hospital human research ethics committee approved the study and consent was obtained from parents/guardians.

Results

Twenty-four families undertook PSM. The median age of children was 11 years and all children had congenital heart disease. A median of 13 INRs was uploaded to the portal per family (range, 8-47) across a 10-month period. Before PSM, the mean time the INR was in therapeutic range was 71%; this increased to 79.9% during PSM (difference: P < .001). No adverse events were encountered. Eight families participated in a phone interview. The major theme identified was empowerment; minor themes that emerged included "gaining knowledge," "trust and responsibility builds confidence," "saving time," and "resources as a safety net."

Conclusion

This study demonstrates that communication via the Epic Patient Portal is satisfactory to families and offers a suitable option for PSM for children. Importantly, PSM empowers and builds confidence in families to facilitate management of their child's health.

A systematic review of adherence to anticoagulation regimens in pediatric patients

Thromboembolic disease rates are increasing in pediatric patients. Anticoagulation is prescribed for treatment and prevention of thromboembolic disease. While nonadherence to anticoagulation regimens predicts poor health outcomes in adults, data in anticoagulated pediatric patients are limited. We systematically reviewed the rates, outcomes, and predictors of anticoagulation nonadherence in the pediatric population. Out of a total of 3581 unique articles identified for review, 17 studies met inclusion criteria. These studies primarily evaluated patients with cardiac disease treated with vitamin K antagonists. Overall nonadherence rates varied from 3% to 42%, based upon population, definition of adherence, and measurement strategy. Patient age, goal international normalized ratio (INR), and number of concurrent potentially interacting medications correlated with nonadherence. Data examining the relationship between nonadherence and health outcomes were included in only two studies. Limitations of current literature, as well as critical knowledge gaps that require future study, are discussed.

FondaKIDS III: A long-term retrospective cohort study of fondaparinux for treatment of venous thromboembolism in children

BACKGROUND

The incidence of venous thromboembolism (VTE) and use of anticoagulation are rising in children, but treatment options remain limited. As a newer anticoagulant, fondaparinux may be a safe and effective alternative with the benefit of once-daily dosing, but there is relatively little data supporting its use.

PROCEDURE

This retrospective cohort study describes the long-term dosing, efficacy, and safety of fondaparinux for treatment of VTE in children at a single institution. The study included children <18 years old treated with fondaparinux for VTE between 2008 and 2018. Descriptive statistics were used to present the findings.

RESULTS

A total of 277 patients were identified and analyzed in this study. Seventy-six percent of patients reached therapeutic levels with 0 or 1 dose adjustments over a median treatment duration of 93 days. Of the patients included in the efficacy analysis, 91% of patients had improvement in their clot status, including 69% (160/233) with complete resolution and 22% (53/233) with partial resolution. Twenty-six patients (11%) had VTE recurrence, but only seven (3%) of the new thrombi developed while on fondaparinux. Major bleeding occurred in seven patients (2.5%), primarily in patients with underlying medical conditions with increased bleeding risk. Minor bleeding occurred in 53 patients (19%).

CONCLUSIONS

This study demonstrates the stable long-term pediatric dosing of fondaparinux with similar efficacy and safety when compared to other anticoagulants. Given its advantages, fondaparinux can be considered a reasonable alternative for treatment of VTE in children.

Participant-reported Warfarin Adherence in Community-based Pediatric Patients

Warfarin is the most commonly prescribed anticoagulant for children in the outpatient setting in Australia. Pediatric patients likely have different challenges to warfarin adherence compared with their adult counterparts; however, little is known about warfarin adherence among this population. This study aimed to understand warfarin adherence among community-based pediatric patients by using an online survey design. The survey instrument incorporated parent or patient self-reported warfarin doses missed in the preceding month, a validated warfarin adherence assessment tool, the 13-item Self-Efficacy for Appropriate Medication use Scale (SEAMS-13), and an open-ended question asking about the challenges of warfarin adherence. The indication of warfarin administration and patient's time in therapeutic range were obtained from medical records. The study recruited outpatients managed by a tertiary pediatric hospital who had previously consented to participate in warfarin research. In total, 53 families were contacted with 43 responses (81% response rate) and 41 completed surveys. The median age of the children from participating families was 10.6 years (range, 4.1 to 18.9 y). The majority of these children (n=42) used warfarin prophylactically and only 1 child used it to treat deep venous thrombosis. The time in therapeutic range achievement of this cohort was 64.4% (95% confidence interval, 58.7-70.2). The mean SEAMS-13 score was 33.5 (95% confidence interval, 31.75-35.37) and the total missed doses was 2.5%. Participants also identified barriers and enablers of warfarin adherence. This study was the first of its kind and thus it provides baseline data for future research. The warfarin adherence of this cohort was likely optimized because of frequent clinical contact and access to self-testing. Future studies are required to examine the different approaches aiming to improve the anticoagulant adherence after the emergence of direct oral anticoagulants with a wider therapeutic index and minimal monitoring that could contribute to less clinical contact.

Personalised Warfarin Dosing in Children Post-cardiac Surgery

Warfarin dosing is challenging due to a multitude of factors affecting its pharmacokinetics (PK) and pharmacodynamics (PD). A novel personalised dosing algorithm predicated on a warfarin PK/PD model and incorporating CYP2C9 and VKORC1 genotype information has been developed for children. The present prospective, observational study aimed to compare the model with conventional weight-based dosing. The study involved two groups of children post-cardiac surgery: Group 1 were warfarin naïve, in whom loading and maintenance doses were estimated using the model over a 6-month duration and compared to historical case-matched controls. Group 2 were already established on maintenance therapy and randomised into a crossover study comparing the model with conventional maintenance dosing, over a 12-month period. Five patients enrolled in Group 1. Compared to the control group, the median time to achieve the first therapeutic INR was longer (5 vs. 2 days), to stable anticoagulation was shorter (29.0 vs. 96.5 days), to over-anticoagulation was longer (15.0 vs. 4.0 days). In addition, median percentage of INRs within the target range (%ITR) and percentage of time in therapeutic range (%TTR) was higher; 70% versus 47.4% and 83.4% versus 62.3%, respectively. Group 2 included 26 patients. No significant differences in INR control were found between model and conventional dosing phases; mean %ITR was 68.82% versus 67.9% (p = 0.84) and mean %TTR was 85.47% versus 80.2% (p = 0.09), respectively. The results suggest model-based dosing can improve anticoagulation control, particularly when initiating and stabilising warfarin dosing. Larger studies are needed to confirm these findings.

Management of thrombosis in children and neonates: practical use of anticoagulants in children

Venous thrombosis (VTE) in children and neonates presents numerous management challenges. Although increasing in frequency, VTE in children and neonates is still uncommon compared with adults. The epidemiology of VTE is vastly different in neonates vs children vs adolescents vs adults. In reality, pediatric thrombosis should be viewed as a multitude of rare diseases (eg, renal vein thrombosis, spontaneous thrombosis, catheter-related thrombosis, cerebral sinovenous thrombosis), all requiring different approaches to diagnosis and with different short- and long-term consequences, but linked by the use of common therapeutic agents. Further, children have fundamentally different physiology in terms of blood flow, developmental hemostasis, and, likely, endothelial function. The American Society of Hematology 2017 Guidelines for Management of Venous Thromboembolism: Treatment of Pediatric VTE provides up-to-date evidence-based guidelines related to treatment. Therefore, this article will focus on the practical use of therapeutic agents in the management of pediatric VTE, especially unfractionated heparin, low-molecular-weight heparin, and oral vitamin K antagonists, as the most common anticoagulants used in children. Direct oral anticoagulants (DOACs) remain in clinical trials in children and should not be used outside of formal trials for the foreseeable future.

UNUSUAL WARFARIN DOSE TO ACHIEVE THERAPEUTIC INR IN A 4-MONTH OLD CHILD: NON-GENETICS RISK FACTORS ARE STILL A CHALLENGE

Objective:

To report a case of a 4-month old girl that required 0.7 mg/kg/day (5 mg) of warfarin and discuss relevant risk factors for requiring higher doses.

Case Description:

In November 2015, a 5 kg female infant (36-week preterm) was admitted to the hospital due to status epilepticus and fever. Diazepam, phenytoin and ceftriaxone were prescribed. Cerebrospinal fluid contained 7 leukocytes, 150 mg/dL proteins, 1 mg/dL glucose and gram positive cocci were observed. Cranial tomography suggested hypodense signs in the cerebellum, right temporal lobe and left basal nuclei, which was consistent with pneumococcal meningitis-induced infectious vasculitis. She required low molecular weight heparin and warfarin for post-encephalitis thrombosis. About 10 days were required to achieve therapeutic INR, and warfarin was adjusted five times since the initial prescription.

Comments:

The risk factors for higher warfarin doses were age and enteral tube feeding. Phenobarbital and prednisone might also have contributed with one of the highest warfarin dose ever reported. Despite current importance given to genetics testing, clinicians should attempt to identify common contributing factors for prolonged non-therapeutic INR, to minimize the risk of coagulation, and to reduce costs of hospital stay and laboratory exams.