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SA JOURNAL OF DIABETES & VASCULAR DISEASE
VOLUME 9 NUMBER 1 • MARCH 2012
29
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IMPROVING WARFARIN CONTROL: CAN
WE ACHIEVE 70% TIME IN THERAPEUTIC
RANGE IN SOUTH AFRICA?
S Afr J Diabetes Vasc Dis
2012;
9
: 29–30.
W
arfarin is used for the management and
prevention of venous thrombo-embolism
(deep-vein thrombosis and pulmonary
embolus) as well as arterial thrombo-embolism.
Lifelong therapy with warfarin is required for the
prevention of systemic embolism in patients with
atrial fibrillation and prosthetic heart valves. During
warfarin initiation, the loading dose is usually 5 or
10 mg. The therapeutic response is measured by the
international normalised ratio (INR) and the dose is
adjusted accordingly.
Warfarin has a narrow therapeutic range and
therefore drug monitoring is essential. The target INR
depends on the indication for warfarin treatment. The
target therapeutic range for venous thromboembo-
lism is 2–3, whereas for double valve replacement,
it is 2.5–3.5. An INR < 2 is usually associated with
thrombotic events and an INR > 4 with haemorrhagic
events.
1
However, the wide inter-individual variability in
therapeutic response poses a major challenge to clini-
cians. This response is determined by genetic as well
as clinical factors (age, gender, body mass index, co-
morbid illnesses) accounting for 30–55% variability.
2,3
In South Africa, good INR control, referred to as the
time in therapeutic range (TTR) has been shown to
be poor. Patients are only protected for about 50% of
the time, according to a study undertaken at Groote
Schuur Hospital’s prothrombin clinic,
4
and the in-
ternational RE-LY study, which also included South
African patients.
Initiatives to improve control that hold promise are
focused on establishing (1) an anti-coagulation man-
agement service which can be nurse, pharmacist or
laboratory service led, and (2) empowering patients
with a self-monitoring device and clear information
on interactional medication and foods that may alter
their warfarin control.
ESTABLISHING AN ANTI-COAGULATION
MANAGEMENT SERVICE
While prothrombin clinics have been established
in some South African hospitals, there is an unmet
need to make the practice of anticoagulation care
more patient-centred, particularly for the elderly who
are most vulnerable to strokes.
PATIENT SELF-MONITORING
Portable, hand-held prothombin time (PT/INR) me-
ters, such as the CoaguChek (R) XS system for pa-
tient self-testing, enable patients to test their clotting
time at home in about a minute, using a small drop
of blood from a simple finger stick. Currently in the
United States, less than 5% of patients on blood thin-
ners perform self-testing, according to the Centers
for Medicare and Medicaid Services.
Studies suggest that anticoagulation patients who
self-test may experience fewer complications overall
than those who do not, because self-testing may in-
crease patient time in the therapeutic range.
5
Studies
also suggest that PT/INR self-testing is just as accu-
rate as finger-stick testing performed by a healthcare
professional and conventional testing performed on
a laboratory analyser.
6-8
All patients on anticoagulant medication need a
prescription from their doctor for a self-testing meter
and supplies, before being able to monitor their own
clotting time at home. Patient self-testing is also de-