Protocol for Past BP: a randomised controlled trial of different blood pressure targets for people with a history of stroke of transient ischaemic attack (TIA) in primary care



Fletcher et al. BMC Cardiovascular Disorders 2010, 10:37
http://www.biomedcentral.com/1471-2261/10/37

Page 3 of 8


The latter point will be explored by economic model-
ling. If there is uncertainty as to whether there is net
benefit from intensive blood pressure lowering, then
there would be a case for a trial of different targets for
BP lowering in primary care that is powered to detect
differences in clinical end-points.

The study will also investigate patientsunderstanding
and beliefs about the relationship between blood pres-
sure and stroke, and patients and healthcare profes-
sionals experience of participating in the study, which
may contribute to the success or otherwise of the
intervention.

Study design and setting

Past BP is a primary care based pragmatic randomised
controlled trial (RCT) in which people with stroke or
TIA are randomised to an intensive blood pressure (BP)
target group (target 130 mmHg systolic, or 10 mmHg
reduction in systolic BP if baseline BP 125 - 140
mmHg) or a standard BP target group (target 140
mmHg systolic).

We will also use qualitative methodologies to investi-
gate patient and healthcare professionals understanding
and views of BP management. Grounded theory meth-
ods will guide sampling, data collection and data analy-
sis [15,16]. Sampling will be done purposively to allow
for the maximum variety of characteristics. Semi-struc-
tured interviews will be carried out [17] and will con-
tinue until new concepts are no longer being generated
and theoretical saturation is reached.

Ethical Considerations

Full ethical approval for this study has been obtained
from Warwickshire Research Ethics Committee, refer-
ence 08/H1211/121. A Data Monitoring Committee and
a Trial Steering Committee will monitor the progress of
the RCT.

Randomised controlled trial

Study Interventions

Management of both treatment groups will follow study
specific treatment protocols that reflect the current
NICE guidelines [18]. However, the thresholds for inter-
vention between the two treatment groups are different:
all patients in the intensive target arm will have their BP
lowering therapy intensified at trial entry since the tar-
get will be automatically below their baseline BP
whereas only those patients in the standard arm whose
BP is above 140/90 mmHg will have their therapy inten-
sified at the outset.

Identification of eligible patients

Eligible patients will be identified from general practices
from the Central England Primary Care Research Net-
work and from the Midlands Research Practice Consor-
tium (MidReC). Each practice will run a search of their
clinical computer system to identify all patients on the
stroke/TIA register. Where possible, the computer
search will exclude patients with clear exclusion criteria
(see table 1). The GP will also remove patients for
whom a study invitation would be inappropriate (for
example, those with a terminal illness). Patients with no
clear exclusion criteria at this stage will be sent a letter
inviting them to attend a study baseline clinic
appointment.

Baseline clinic appointment

This clinic appointment is carried out by a Research
Nurse. At this appointment the nurse will: confirm the
stroke/TIA diagnosis through review of medical records
and patient interview; determine whether there are any
exclusion criteria present; and collect baseline data (see
table 2). If the patient is eligible and willing to take part,
the nurse will also gain written informed consent prior
to randomisation, and will telephone the randomisation
service to obtain treatment group allocation.

Once the treatment allocation has been obtained,
patients in the intensive target group and any patients
who have been randomised to the standard treatment
group whose BP is above the target of 140 mmHg will
see a GP in order to have their treatment intensified
using the study specific treatment protocol (see figure 1).
Patients in the standard group whose BP is below target
will receive an appointment to see the practice nurse
three months post randomisation.

Randomisation

The randomisation will use minimisation to balance the
randomised groups on the basis of age (<80,
80), sex,
diabetes mellitus, atrial fibrillation (because of the diffi-
culties of obtaining accurate BP measurements in this
group), baseline systolic BP and practice.

Patient follow-up procedures

Patients will be followed up from trial e ntry for 12
months. Follow up will be carried out in several ways.
Firstly, practice nurses (PNs) will see patients at 1-3
monthly intervals, depending on BP and treatment allo-
cation. (see figure 2) The PN will take a patient
s BP and
refer them to the GP if the BP is above target, or if the
patient is having problems with adverse effects to their
BP medication. The GP will then adjust the medication,
following the study treatment protocol (see figures 1). At
6 and 12 months patients will be followed up by a
research nurse (RN) where details of primary and sec-
ondary outcomes will be collected. (see table 2). Finally,
the records of patients will be flagged at the NHS Central
Register.

Patient outcome measures

The primary outcome measure is a change in systolic
blood pressure between baseline and 12 months. Blood
pressure measurements are performed in a standardised
way, using BHS validated automated electronic monitors



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