Apixaban for the prevention of venous thromboembolism in people ...

2 BACKGROUND
2.1 Critique of manufacturer’s description of underlying health problem.
Does the ERG believe that the manufacturer’s description of the underlying health problem is
appropriate and relevant to the decision problem under consideration?
The ERG largely agrees with the description of the underlying health problem. It is not clear whether
the incidence, prevalence, mortality and costing are directly linked to THR or TKR, or VTE in
general. Additionally, it is unclear if the VTE described is caused by either THR or TKR, or as a
result of other factors, or in combination. The ERG provides a detailed overview on VTE (DVT and
PE), THR and TKR.
Venous Thromboembolism is a collective term for two conditions namely deep vein thrombosis
(DVT) which is the most common type of VTE, and pulmonary embolism (PE). DVT occurs when
there is a formation of a blood clot in the veins of the legs whereas PE occurs when a blood clot forms
in one of the blood vessels in the lungs. 1 In the United Kingdom, VTE affects 1 in 1000 people, and
around one in 10 persons with untreated DVT develop PE. 2 The risk of developing VTE is dependent
on the patients’ health, surgical procedure to be undertaken, and other predisposing factors such as
age, genetics, medical conditions, obesity and pregnancy. Persons undergoing orthopaedic surgery
including knee and hip replacement have an increased risk, and the majority of affected patients
develop DVT and PE while in hospital. 3 The typical symptoms of DVT include swelling, tenderness
to the leg muscles and skin discoloration (reddish or bluish) whereas PE symptoms include mild
fever, sudden shortness of breath, rapid heart rate and sometimes patients may present with DVT
symptoms such as swelling to the legs. Nonetheless, in some cases such symptoms may not be
present, which is suggestive of why VTE is at times called a “silent killer”. 4 The incidence and
prevalence rates of VTE outside the hospital environment are unknown. 3 The diagnosis is often
assessed by prevailing symptoms in combination with a relevant test such as D-dimer test, ultrasound
scan, venogram and a Doppler study for DVT, while the PE diagnosis is based on use of a
computerised tomography pulmonary angiograph (CTPA), ventilation (perfusion) scan or D-dimer
test. PE is the primary cause of death in 10% of all hospitalised patients, with related annual mortality
figures of 25,000 and 32,000 for DVT and PE respectively. 2 The mortality figures for VTE exceed the
pooled total deaths from acquired immune deficiency syndrome (AIDS), breast cancer and traffic
accidents. 2 However, the figures are often used as a guide rather than the definite number of deaths.
This is because the deaths are usually not followed by a post-mortem or are either recorded as those
caused by a heart attack or acute respiratory failure. 3 The majority of deaths are thought to be
preventable by appropriate reference to the NICE guideline 3 on prevention of VTE in hospitalised
persons (use of thromboprophylaxis during hospital and after discharge). The direct and indirect cost
2, 5
of currently managing VTE is projected at £640 million annually.
The THR and TKR surgery is grouped in to three main types of operations. These include primary
procedures, revision procedures, and re-operation other than revision procedures. Primary surgery
represents the majority of TKR and TKR operations. There has been a gradual increase in the number
of TKR procedures compared to THR. In 2005/06 TKR represented a 2.1% and 5.5% in 2009/10
increase in primary procedures over THR. 6
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