The American Society of Hematology (ASH), the world's largest professional society concerned with the causes and treatment of blood disorders in partnership with the McMaster University GRADE Centre, a world leader in guideline development and an authority on thrombosis announced the 2018 ASH Clinical Practice Guidelines on Venous Thromboembolism (VTE). The guidelines have been published in the journal Blood Advances and includes six chapters, four more chapters are in development.

VTE, a term referring to blood clots in the veins, is a highly prevalent and far-reaching public health problem that can cause disability and death. Blood clots can affect anyone – from the healthy to the chronically ill – in a variety of settings, including pregnant women, children, and people who are hospitalized, meaning that the burden of effective prevention, diagnosis, and treatment falls on a broad range of physicians.

The 10 evidence-based clinical guidelines chapters cover VTE through a number of lenses, in areas in which there is currently uncertainty and variation in clinical practice:

• Prophylaxis for hospitalized and non-hospitalized medical patients
• Diagnosis of VTE
• Optimal management of anticoagulation therapy
• Heparin-induced thrombocytopenia
• VTE in the context of pregnancy
• Treatment of pediatric VTE
• Treatment of deep-vein thrombosis and pulmonary embolism (anticipated in 2019)
• VTE in patients with cancer (anticipated in 2019)
• Thrombophilia (anticipated in 2019)
• Prevention of VTE in surgical patients (anticipated in 2019)

Presented below is a high-level summary of the first six chapters of the ASH guidelines on VTE

1. Prophylaxis for Hospitalized and Non-Hospitalized Medical Patients (Total number of recommendations:21)

What it covers
• Who should receive an intervention and what that intervention should be
• Interventions considered include blood thinning medications of different types and mechanical compression (e.g., pneumatic compression devices or graduated compression stockings)

Who it affects
• Medical inpatients (including those in intensive care units), long-term care residents, persons with minor injuries, and long-distance travelers (>4 hours by air)
• Health care providers working in hospitals

What are the highlights
• In medical inpatients at high bleeding risk who require prophylaxis, mechanical prophylaxis is preferred over blood-thinning medications
• In medical inpatients at high VTE risk but acceptable bleeding risk, blood thinning medication is preferred over mechanical prophylaxis
• In medical inpatients, when medication is used to prevent VTE, low-molecular-weight heparin is preferred over unfractionated heparin because it is only administered once a day and has fewer complications
• In medical inpatients, when a medication is used to prevent VTE, low-molecular-weight heparin during the hospital stay is preferred over a direct oral anticoagulant administered in hospital or after discharge
• The use of combined modalities in medical inpatients (e.g., compression devices plus a blood thinner) is not necessary
• Long-distance air travelers who do not have an elevated risk of thrombosis do not need to wear compression socks or take a blood thinner like aspirin to prevent thrombosis. Air travelers at substantially increased risk may benefit from graduated compression stockings or low-molecular-weight heparin

2. Diagnosis of VTE (Total number of recommendations:10)

What it covers
Efficient diagnostic strategies for evaluating patients with suspected VTE to provide accurate diagnosis and reduce the number of patients undergoing unnecessary and more invasive testing

Who it affects
• Patients with suspected VTE
• Clinicians and health care professionals

What are the highlights
• Unlike other VTE diagnosis guidelines, mathematical modelling was done to predict outcomes of various diagnostic pathways that have not been previously evaluated
• Before considering a test, categorizing patients into the likelihood that they have VTE will help achieve an accurate diagnosis without exposing the patient to unnecessary testing
• A D-dimer test is the best first step to check for VTE in patients with low pre-test probability; if results are negative, no further testing is required
• When possible, clinicians should use a VQ scan, which exposes patients to lower radiation risk, versus a CT scan. Older individuals or those with preexisting lung disease are not ideal candidates for a VQ scan.

3. Optimal Management of Anticoagulation Therapy (Total number of recommendations:25)

What it covers
Optimal care management of anticoagulation therapy in patients who have previously experienced a clot

Who it affects
• Patients who have already had a blood clot and need to take anticoagulant drugs
• Pharmacists, clinicians, nurses, and health care policy makers

What are the highlights
• Most patients needing to interrupt warfarin for invasive procedures do not require a short-acting injectable anticoagulant administered during the peri-operative period, so called bridge therapy
• Many patients who survive major bleeding during anticoagulant therapy should resume taking anticoagulants

What it covers
A rare and serious adverse drug reaction that increases a patient’s risk of developing venous or arterial thromboembolism, which may be limb- or life-threatening

Who it affects
• Surgical patients most commonly, especially those undergoing cardiac surgery
• Hospitalists, surgeons, and cardiologists

What are the highlights
• Using a clinical scoring system, the 4Ts score, rather than a gestalt approach will improve the accuracy of diagnosis and patient outcomes
• Treatment options include not only conventional agents such as argatroban, bivalirudin, and danaparoid, but also newer agents such as fondaparinux and the direct oral anticoagulants

What it covers
The diagnosis, prevention, and treatment of VTE during and after pregnancy, which are particularly challenging issues due to the need to consider fetal as well as maternal well-being

Who it affects
• Pregnant women, especially those who have previously experienced a blood clot or have other risk factors for blood clots
• Obstetrician-gynecologists, maternal fetal specialists, and internists

What are the highlights
• In the majority of cases, low-molecular-weight heparin is likely to be the best approach for managing superficial thrombosis
• For treatment of pulmonary embolism and deep-vein thrombosis with low-molecularweight heparin, it is acceptable to do weight-based dosing instead of using regular blood tests to adjust the dose
• A majority of pregnant women with newly diagnosed VTE at low risk of complications can be treated as outpatients

What it covers
Sometimes DVT causes symptoms, and sometimes it is found incidentally in an imaging study for something else. These guidelines inform how to treat these different situations. This distinction has not been addressed by guidelines in the past.

Who it affects
• Very ill children, newborns through 18 years of age; most common in small children and teenagers
• Pediatricians, pediatric hematologists, pediatric oncologists, pediatric intensivists, and neonatologists

What are the highlights
• Central venous line-associated clots are the most common clots in children
• If the central venous line is not working and the child is at the end of treatment, it should most likely be removed
• Renal vein thrombosis, the most common spontaneous VTE in children, should all receive anticoagulation therapy

About the American Society of Hematology (ASH)
The American Society of Hematology (ASH) is the world's largest professional society of hematologists dedicated to furthering the understanding, diagnosis, treatment, and prevention of disorders affecting the blood. For more than 50 years, the Society has led the development of hematology as a discipline by promoting research, patient care, education, training, and advocacy in hematology.

Note: This list is a brief compilation of some of the key recommendations included in the Guidelines and is not exhaustive and does not constitute medical advice. Kindly refer to the original publications here:
1. https://pxmd.co/7a5cx
2. https://pxmd.co/VMGKd
3. https://pxmd.co/c2Qrh
4. https://pxmd.co/LuUPr
5. https://pxmd.co/ayDKL
6. https://pxmd.co/WvPeI

#JustReleased: ASH Clinical Practice Guidelines on VTE