Variation in warfarin prescribing and dosing in the UK: a national survey of anticoagulation clinics

Pharmacogenetics to guide cardiovascular drug therapy

Over the past decade, pharmacogenetic testing has emerged in clinical practice to guide selected cardiovascular therapies. The most common implementation in practice is CYP2C19 genotyping to predict clopidogrel response and assist in selecting antiplatelet therapy after percutaneous coronary intervention. Additional examples include genotyping to guide warfarin dosing and statin prescribing. Increasing evidence exists on outcomes with genotype-guided cardiovascular therapies from multiple randomized controlled trials and observational studies. Pharmacogenetic evidence is accumulating for additional cardiovascular medications. However, data for many of these medications are not yet sufficient to support the use of genotyping for drug prescribing. Ultimately, pharmacogenetics might provide a means to individualize drug regimens for complex diseases such as heart failure, in which the treatment armamentarium includes a growing list of medications shown to reduce morbidity and mortality. However, sophisticated analytical approaches are likely to be necessary to dissect the genetic underpinnings of responses to drug combinations. In this Review, we examine the evidence supporting pharmacogenetic testing in cardiovascular medicine, including that available from several clinical trials. In addition, we describe guidelines that support the use of cardiovascular pharmacogenetics, provide examples of clinical implementation of genotype-guided cardiovascular therapies and discuss opportunities for future growth of the field.

Risk of significant traumatic brain injury in adults with minor head injury taking direct oral anticoagulants: a cohort study and updated meta-analysis

BACKGROUND

Patients taking direct oral anticoagulants (DOACs) commonly undergo CT head imaging after minor head injury, regardless of symptoms or signs. However, the risk of intracranial haemorrhage (ICH) in such patients is unclear, and further research has been recommended by the UK National Institute for Health and Care Excellence head injury guideline group.

METHODS

An observational cohort study was performed in the UK South Yorkshire major trauma centre between 26 June and 3 September 2018. Adult patients taking DOACs with minor head injury were prospectively identified, with case ascertainment supplemented by screening of radiology and ED information technology systems. Clinical and outcome data were subsequently collated from patient records. The primary endpoint was adverse outcome within 30 days, comprising: neurosurgery, ICH or death due to head injury. A previously published meta-analysis was updated with the current results and the findings of other recent studies.

RESULTS

148 patients with minor head injury were included (GCS 15, n=107, 72%; GCS 14, n=41, 28%). Patients were elderly (median 82 years) and most frequently injured from ground level falls (n=142, 96%). Overall risk of adverse outcome was 3.4% (5/148, 95% CI 1.4% to 8.0%). Five patients had ICH, of whom one died within 30 days. One patient was treated with prothrombin complex concentrate but no patient received critical care management or underwent neurosurgical intervention. Updated random effects meta-analysis, including the current results and two further recent studies, showed a weighted overall risk of adverse outcome of 3.2% (n=29/787, 95% CI 2.0% to 4.4%).

CONCLUSIONS

The risk of adverse outcome following mild head injury in patients taking DOACs appears low. These findings would support shared patient-clinician decision making, rather than routine imaging, following minor head injury while taking DOACs.

Warfarin Management and Outcomes in Patients with Nonvalvular Atrial Fibrillation Within an Integrated Health Care System

BACKGROUND

Warfarin is a common treatment option to manage patients with nonvalvular atrial fibrillation (NVAF) in clinical practice. Understanding current pharmacist-led anticoagulation clinic management patterns and associated outcomes is important for quality improvement; however, currently little evidence associating outcomes with management patterns exists.

OBJECTIVES

To (a) describe warfarin management patterns and (b) evaluate associations between warfarin treatment and clinical outcomes for patients with NVAF in an integrated health care system.

METHODS

A retrospective cohort study was conducted among NVAF patients with warfarin therapy between January 1, 2006, and December 31, 2011, using Kaiser Permanente Southern California data, and followed until December 31, 2013. Management patterns related to international normalized ratio (INR) monitoring, anticoagulation clinic pharmacist intervention (consultation), and warfarin dose adjustments were investigated along with yearly attrition rates, time-in-therapeutic ranges (TTRs), and clinical outcomes (stroke or systemic embolism and major bleeding). Descriptive statistics and multivariable Cox proportional hazard models were used to determine associations between TTR and clinical outcomes.

RESULTS

A total of 32,074 NVAF patients on warfarin treatment were identified and followed for a median of 3.8 years. About half (49%) of the patients were newly initiating warfarin therapy. INR monitoring and pharmacist interventions were conducted roughly every 3 weeks after 6 months of warfarin treatment. Sixty-three percent of the study population had ≥ 1 warfarin dose adjustments with a mean (SD) of 6.7 (6.3) annual dose adjustments. Warfarin dose adjustments occurred at a median of 1 day (interquartile ranges [IQR] 1-3) after the INR measurement. Yearly attrition rate was from 3.3% to 6.3% during the follow-up, and median (IQR) TTR was 61% (46%-73%). Patients who received frequent INR monitoring (≥ 27 times per year), pharmacist interventions (≥ 24 times per year), or frequently adjusted warfarin dose (≥ 11 times per year) consistently showed poor TTRs (mean TTR for the highest quartiles was 45.3%-48.3%). A higher TTR was associated with a lower risk of clinical outcomes regardless of frequency of INR monitoring, pharmacist interventions, or number of dose adjustments. Patients whose TTRs were < 65%, even with frequent pharmacist interventions, had similar stroke or systemic embolism event rates, as compared with patients with TTRs < 65% and less frequent interventions (1.88 vs. 1.54 stroke or systemic embolism rates per 100 person-years, respectively, P = 0.78). The lowest TTR quartile (< 46%) was associated with a 3 times higher risk of stroke or systemic embolism (hazard ratio [HR] = 3.19, 95% CI = 2.71-3.77) and a 2 times higher risk of major bleeding (HR = 2.10, 95% CI = 1.96-2.24) compared with the highest TTR quartile (≥ 73%).

CONCLUSIONS

Despite close monitoring with timely warfarin dose adjustments, there were still a substantial number of challenging patients whose TTRs were suboptimal despite a higher number of pharmacist interventions. These patients eventually experienced more stroke or systemic embolism and bleeding events among NVAF patients managed by anticoagulation clinics. New individualized treatment or management strategies for patients who are not able to reach optimal therapeutic ranges are necessary to improve outcomes.

DISCLOSURES

This research and manuscript were funded by Bristol-Myers Squibb Company and Pfizer. Authors from Bristol-Myers Squibb Company and Pfizer participated in the design of the study, interpretation of the data, review/revision of the manuscript, and approval of the final version of the manuscript. An received a grant for research support from Bristol-Myers Squibb/Pfizer. Niu, Rashid, and Zheng received a grant from Bristol-Myers Squibb/Pfizer to their institutions for salary reimbursement. Vo, Singh, and Aranda are employed by Bristol-Myers Squibb; Bruno was employed by Bristol-Myers Squibb at the time of this study. Mendes and Dills are employed by Pfizer, and Mendes was a member of the Pfizer Cardiovascular and Metabolic Field Medical Team during the time of this study. Lang, Jazdzewski, and Le have no known conflicts of interest to report. Study concept and design were contributed primarily by An and Rashid, along with the other authors. Niu took the lead in data collection, along with Zheng, and data interpretation was performed by An, along with Mendes and Dills, with assistance from the other authors. The manuscript was written by An and revised by Mendes, Dills, Vo, Singh, Bruno, and Aranda, along with Lang, Le, and Jazdezewski. Part of this study's findings was presented at the CHEST 2015 Annual Meeting in Montreal, Canada, on October 28, 2015.

Warfarin monitoring in nursing homes assessed by case histories. Do recommendations and electronic alerts affect judgements?

PURPOSE

Older adults treated with warfarin are prone to complications, and high-quality monitoring is essential. The aim of this case history based study was to assess the quality of warfarin monitoring in a routine situation, and in a situation with an antibiotic-warfarin interaction, before and after receiving an electronic alert.

MATERIALS AND METHODS

In April 2014, a national web-based survey with two case histories was distributed among Norwegian nursing home physicians and general practitioners working part-time in nursing homes. Case A represented a patient on stable warfarin treatment, but with a substantial INR increase within the therapeutic interval. Case B represented a more challenging patient with trimethoprim sulfamethoxazole (TMS) treatment due to pyelonephritis. In both cases, the physicians were asked to state the next warfarin dose and the INR recall interval. In case B, the physicians could change their suggestions after receiving an electronic alert on the TMS-warfarin interaction.

RESULTS

Three hundred and ninety eight physicians in 292 nursing homes responded. Suggested INR recall intervals and warfarin doses varied substantially in both cases. In case A, 61% gave acceptable answers according to published recommendations, while only 9% did so for case B. Regarding the TMS-warfarin interaction in case history B, the electronic alert increased the percentage of respondents correctly suggesting a dose reduction from 29% to 53%. Having an INR instrument in the nursing home was associated with shortened INR recall times.

CONCLUSIONS

Practical advice on handling of warfarin treatment and drug interactions is needed. Electronic alerts as presented in electronic medical records seem insufficient to change practice. Availability of INR instruments may be important regarding recall time.

DNA sensors to assess the effect of VKORC1 and CYP2C9 gene polymorphisms on warfarin dose requirement in Chinese patients with atrial fibrillation

The optimal dose of warfarin depends on polymorphisms in the VKORC1 (the vitamin K epoxide reductase complex subunit (1) and CYP2C9 (cytochrome P450 2C9) genes. To minimize the risk of adverse reactions, warfarin dosages should be adjusted according to results from rapid and simple monitoring methods. However, there are few pharmacogenetic-guided warfarin dosing algorithms that are based on large cohorts from the Chinese population, especially patients with atrial fibrillation. This study aimed to validate a pharmacogenetic-guided warfarin dosing algorithm based on results from a new rapid electrochemical detection method used in a multicenter study. Three SNPs (CYP2C9 *2, *3 and VKORC1 c.-1639G > A) were genotyped by electrochemical detection using a sandwich-type format that included a 3' short thiol capture probe and a 5' ferrocene-labeled signal probe. A total of 1285 samples from four clinical hospitals were evaluated. Concordance rates between the results from the electrochemical DNA biosensor and the sequencing test were 99.8%. The results for gene distribution showed that most Chinese patients had higher warfarin susceptibility because mutant-type and heterozygotes were present in the majority of subjects (99.4%) at locus c.-1639G > A. When the International Warfarin Pharmacogenetics Consortium algorithm was used to estimate therapeutic dosages for 362 patients with AF and the values were compared with their actual dosages, the results revealed that 56.9% were similar to actual dosages (within the 20% range). A novel electrochemical detection method of CYP2C9 *2, *3and VKORC1 c.-1639G > A alleles was evaluated. The warfarin dosing algorithm based on data gathered from a large patient cohort can facilitate the reasonable and effective use of warfarin in Chinese patients with AF.