3 Clinical need and practice
3.1 The point‑of‑care coagulometers are designed to monitor the clotting tendency of blood in people on long‑term vitamin K antagonist therapy, such as those with atrial fibrillation or artificial heart valves who are at risk of thrombosis. The tests allow monitoring by 2 different methods of care: self‑testing and self‑managing. Both methods are based on the international normalised ratio (INR), which is a standardised unit for measuring the time it takes for blood to clot. Self‑testing refers to the user doing the INR test themselves and then contacting their healthcare professional with the reading for advice on any change to the dosage of the anticoagulant that may be needed. Self‑managing refers to the user doing the INR test themselves and then self‑adjusting the dosage of their anticoagulant medication by following an agreed care protocol. Together, these methods of care are referred to as self‑monitoring.
3.2 The use of these coagulometers may reduce the frequency of visits to hospital or clinics for patients and enable them to be monitored more regularly. This may improve health outcomes by enabling the dose of therapy to be adjusted more accurately, thereby avoiding adverse events that can result from an over‑ or under‑dose of long‑term vitamin K antagonist therapy, such as stroke and major haemorrhage.
3.3 The purpose of this assessment is to evaluate the clinical and cost effectiveness of using the CoaguChek XS system and the INRatio2 PT/INR monitor for self‑monitoring (self‑testing or self‑managing) coagulation status in people on long‑term vitamin K antagonist therapy who have atrial fibrillation or heart valve disease.
3.4 There are a number of conditions that can result in people having an increased risk of thrombosis and consequently, receiving long‑term vitamin K antagonist therapy. These conditions include atrial fibrillation and heart valve disease. Guidance on self‑monitoring the coagulation status of people who have had a venous thromboembolism and are receiving long‑term vitamin K antagonist therapy is included in the NICE guideline on venous thromboembolic diseases and so this population is not included in the scope of this diagnostics assessment of self‑monitoring coagulometers.
3.5 Atrial fibrillation is the most common heart arrhythmia and affects around 800,000 people in the UK. It can affect adults of any age but it is more common in older people; 0.5% of people aged 50–59 years and around 8% of people aged over 65 years are estimated to be affected. Atrial fibrillation is also more common in men than women, and is more common in people with other conditions, such as high blood pressure, atherosclerosis and heart valve problems.
3.6 Approximately 47% of people with atrial fibrillation currently receive vitamin K antagonist therapy. It is estimated that a further 30% of people with atrial fibrillation could receive this therapy but currently do not. People with atrial fibrillation are at a 5–6 times greater risk of stroke, with 12,500 strokes directly attributable to atrial fibrillation occurring every year in the UK. Treatment with warfarin reduces this risk by 50–70%.
3.7 Valve disease can affect blood flow through the heart in 2 ways: valve stenosis, in which the valve does not open fully, and valve regurgitation (or incompetence) in which the valve does not close properly, allowing blood to leak backwards. Disease can occur in any of the 4 heart valves, although disorders of the aortic and mitral valves are more serious.
3.8 The main causes of heart valve disease are congenital heart disease and other diseases such as rheumatic fever, lupus, cardiomyopathy and endocarditis. Aortic stenosis is the most common type of valve disease and it affects around 1 in 20 adults over the age of 65 years in the UK.
3.9 Data from the UK heart valve registry indicate that approximately 0.2% of the UK population has prosthetic heart valves. Around 6500 adult heart valve replacements (using mechanical or biological valves) are carried out each year, of which around 5000 are aortic valve replacements.
3.10 Patients with mechanical heart valves (and some patients with bioprosthetic valves) are susceptible to thromboembolism and need lifelong anticoagulant therapy.
3.11 Non‑vitamin K antagonist oral anticoagulants are an alternative to vitamin K antagonists and can be administered to reduce the risk of thrombosis or stroke. The non‑vitamin K antagonist oral anticoagulants have fewer food and drug interactions than vitamin K antagonists and they do not need therapeutic monitoring. However, they may be unsuitable for some people, such as people with mechanical heart valves, certain people with renal or liver dysfunction and those taking concurrent drugs that cannot be taken with the non‑vitamin K antagonist oral anticoagulants. The individual summary of product characteristics should be consulted for specific details when prescribing a non‑vitamin K antagonist oral anticoagulant. NICE technology appraisal guidance recommends 3 non‑vitamin K antagonist oral anticoagulants (see the NICE guidance on apixaban, rivaroxaban and dabigatran etexilate) for preventing stroke and systemic embolism in people with non‑valvular atrial fibrillation.
3.12 Guidelines on oral anticoagulation with warfarin, published by the British Committee for Standards in Haematology (Keeling et al. 2011), outline the process for INR monitoring for those receiving warfarin. The NICE clinical knowledge summary for oral anticoagulation states that INR can be most accurately measured in venous blood samples, but that capillary blood samples are also used because they are more convenient. People being tested should receive a written copy of their INR result including any necessary dose adjustments and a date for the next check.
3.13 The summary states that the INR should be measured:
daily, or on alternate days, until it is within the therapeutic range (usually between 2.0 and 3.0, ideally 2.5) on 2 consecutive occasions
then twice weekly for 1–2 weeks, followed by weekly measurements until the INR is stable within the therapeutic range
thereafter, depending on the stability of the INR, at longer intervals (for example, up to every 12 weeks, if agreed locally).
3.14 More frequent monitoring of the INR is recommended for patients at risk of overcoagulation or bleeding, or those having problems adhering to treatment. Intravenous drug users, and people with hepatitis B, hepatitis C, or HIV, may be referred to a specialist clinic according to local arrangements.
3.15 INR monitoring can be managed by local anticoagulant clinics in primary care, but sometimes clinics are based in secondary care, involving travel to hospital. The NICE anticoagulation commissioning guide (2013) states that anticoagulation therapy services can be delivered in a number of different ways, and that mixed models of provision may be needed across a local health region. This could include full service provision in secondary or primary care, shared provision, domiciliary provision and self‑management. Services may be managed by a range of healthcare professionals including nurses, pharmacists and general practitioners.