The low-down on
DXA scanning
Nurses should have
the knowledge and
education to request
DXA scans and instigate
early treatment, writes
Susan Vanderkamp
O
Nurses working in many different specialities
encounter osteoporosis. All too often, osteoporosis is undetected until a fracture occurs, and
when this happens, it is a matter of treating to
prevent further fracture.
In an ideal healthcare system, nurses who
work in primary and secondary care should
have the knowledge and education regarding
osteoporosis prevention to detect those who are
at risk of osteoporosis, to request a DXA in those
patients, and to instigate early treatment and
future fracture prevention.
steoporosis is a reduction in the strength of
bone that predisposes to fracture. Osteoporosis is defined as a chronic systemic skeletal
disease characterised by low bone mass and
micro-architectural deterioration of bone tissue,
with a consequent increase in bone fragility and
susceptibility to fracture.1 It is a silent disease
until it manifests with fracture, especially in the
spine, wrist and hip. Osteoporotic fractures arise
through a combination of reduced bone strength
and trauma. A low-trauma fracture at one skeletal site is a strong predictor of fractures at other
sites. Early detection of osteoporosis is possible
by measuring bone mineral density (BMD) using a
dual-energy x-ray absorptiometry (DXA) machine.
Osteoporosis is not the preserve of any one
medical speciality but many (endocrinology, geriatrics, gynaecology, rheumatology and general
practice). It often falls between stools and is not
recognised as a serious life-threatening condition.
Setting up a DXA nurse-led service
Setting up a DXA centre is a challenge to
the service provider in that it entails undertaking
considerable research and hard work into how it
can be run and managed in keeping with international guidelines. Wherever a bone density unit is
located – hospital-based or in general practice –
certain standards have to be adhered to.
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referral form, or by a GP who has sent a referral
letter. It is illegal to scan without a referral letter. An information booklet regarding the DXA
procedure and osteoporosis, including information on treatments, is an ideal way of imparting
information on osteoporosis and should be a
back-up to the patient interview and DXA scan. It
is preferable to ask the patient to complete an assessment questionnaire that outlines risk factors
and medications.
In 1994, a WHO technical report introduced
a classification system for osteoporosis based on
BMD measurement at the femoral neck – namely,
the T-score, which is a means of expressing the
result in standardised units according to the reference population of healthy young adults.3
In 2008, the same WHO group introduced
FRAX, that shifts the clinical paradigm from
risk categorisation to fracture-risk estimation in
adults.4 The 10-year per cent probabilities of hip
and major osteoporotic fractures are calculated
by combining a T-score result with risk factors
(age, previous fracture, parent fractured hip, current smoking, alcohol intake, glucocorticoids and
rheumatoid arthritis).
A typical scan session with a patient takes
approximately 30 minutes. Within this half-hour
allocation, the patient receives an education assessment in relation to diet, lifestyle, exercise and
fall prevention, as well as information regarding
any medications which they may be prescribed.
There are rules relating to medication ingestion which need to be observed, eg. the use of
bisphosphonates requires taking the medication
in the fasting state with a 200ml glass of plain
water, not fruit juice or milk. When taking two
calcium supplements, the doses should be divided
into one supplement in the morning and one in
the evening.
Knowledge of these rules enables better
understanding of medication by the patient and
helps towards better compliance. Compliance
with medication is low, especially with bisphosphonate use. Nurse education on giving a patient
One of the biggest challenges for nurses
working in the area has been in relation to radiation protection, which traditionally has not been
part of nurse training. In 2006, draft legislation
(Statutory Instrument 478 [section 13.2]) allows
any person who has undertaken a radiation protection course to work with radiation. This draft
document has established a pathway that permits
nurses to operate DXA machines.
All personnel involved in running a DXA unit
have to be trained in DXA scanning technique,
and have to attend a course in radiation protection; this should be repeated at two-yearly intervals. Initial manufacturer training by the company
providing the DXA machine is provided to start
off training and the rule of thumb is to scan, scan
and scan as many patients as possible to build up
experience.
It is normal that when a 100 or more scans
have been carried out, further training with
certification should be undertaken. The nearest
training centre for Ireland is in the UK and there is
strong collaboration between the two countries.
Most nurses working in DXA in Ireland undergo
a certification exam with the National Osteoporosis Society in the UK. When a new nurse starts
working in a unit, it is usual to have a two-week
training period with the longest trained nurse in
the unit to build up experience.
Department protocol
A department working protocol is necessary for the day-to-day running of DXA centres
and should be based on the most up-to-date
international guidelines. The International Society
for Clinical Densitometry (www.iscd.org) has
recently updated its official positions.2 This is
a not-for-profit multidisciplinary professional
society; its mission is to advance excellence in the
assessment of skeletal health by standard setting,
increasing patient awareness and continuing
medical education
Holistic procedure
In most centres, patients are referred for a
DXA scan by a physician who has written a DXA
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Simple walking is safe for everyone.
Much time is spent ‘thinking’ about getting up and going for a walk, but it can
be as simple as walking to the local shop
for the newspaper and walking back,
instead of driving in a car. Swimming
provides good aerobic exercise, and helps
with pain relief after fractures, but it is
not a weight-bearing exercise.
Having input from a dietitian is ideal
to emphasise the importance of daily
calcium through the diet (milk, cheese
and yoghurts) and daily intake of vitamin
D, (mackerel, sardines, cereals, margarine
spreads) which aids calcium absorption. Being
outside pottering in the garden while being
exposed to early morning or late afternoon sunlight, between April and October for 10 minutes
a day is usually sufficient for top-up of vitamin D
levels (it is wise to avoid midday sun).
Many people, due to restrictive dieting or
excessive caffeine intake (more than five cups of
strong tea/coffee per day), run the risk of developing osteoporosis. Too much caffeine increases
urinary calcium excretion. With excess alcohol
intake, calcium absorption is hindered, and
often combinations of dieting, with an excess of
alcohol and an absence of dietary dairy calcium,
sets the stage for the development of bone loss
later in life.
For the elderly patient, advice on safety
at home with a view to fall prevention from a
community occupational therapist cannot be
emphasised enough. The occupational therapist,
by helping the patient to focus on activities of
daily living, self-care and leisure, aims to enable
the patient to be as independent as possible in
their day-to-day lives.
By adapting the environment or specific
tasks, maximum independence and quality of
life is enhanced. For example, insertion of an
extra rail on stairways, or rails in the bathroom,
non-slip bathmats or use of bathboards can help.
Community services available such as ‘disabled
a good understanding of their medications may improve compliance.
The scan time itself is quite
short (approximately two minutes).
Clothing adjustments for any metal
artefacts such as belts or buttons
or bra wires also has to be factored
in and providing gowns is wise to
avoid unnecessary artefacts within
the regions of interest scanned. The
effective radiation dose to patients
following scanning procedure of the
spine and hip is the equivalent of
one day’s natural background radiation; thus it is quite low. Height and weight are
also recorded before the scan.
Multidisciplinary approach
Information on lifestyle changes – such as
cessation of smoking, assessment of alcohol use
(14 units for a woman and 21 units for a man),
patient education in relation to prevention of
osteoporosis by healthy eating habits and fall
prevention – all form part of the osteoporosis
session.
A multidisciplinary approach that includes
advice about both medications and means of
optimising bone health by exercise, diet, and
activities of daily living (fall prevention) is beneficial. Input from a chartered physiotherapist to
whom the patient can be referred on a finding of
osteoporosis, or for an elderly patient who has a
tendency to fall, is extremely helpful.
From childhood to the mid-20s, exercise is
vital in maximising peak bone mass, a key determinant of bone mass later in life. In later life,
exercise can help to slow down the normal loss of
bone density, and is necessary to general health.
Exercise improves muscle strength and flexibility, improves balance and co-ordination, thus
reducing the risk of falls. Weight-bearing and
muscle-strengthening exercises, targeting arms,
legs and trunk, or posture and balance exercises,
eg. pilates, or Tai Chi, all go towards maintaining
better bone strength.
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pa ti en
persons grant’, pendant alarms, and ‘security
for the elderly’, all go towards an independent
lifestyle, particularly for those living alone.
maintenance has to be factored into a department’s or a practice’s overheads. The maintenance is normally carried out by the service
agent providing the machine. If a machine is
moved or relocated from one area to another, it
is necessary for recalibration to be carried out by
the company. It is important that service logs are
maintained and available for inspection.
Quality assurance
Precision assessment
Finally, all DXA units have to be registered
with the Radiological Institute of Ireland (RPII). A
copy of local radiation rules should be on display
on the office wall at all times. The cornerstone
of operation in a DXA unit is the quality control
for DXA scanning. Within this remit there are
operator-dependent factors (training) and scanning dependent factors.
The scanning dependent factors include in
particular the scanning of ‘phantoms’ on a daily
basis in order to monitor instrument performance and calibration, namely instrument quality
control (IQC). The performance of IQC following
manufacturer’s instructions must be adhered to.
Attention to the correct positioning of the phantom, with acquisition and scan analysis of results
is important. The phantom should be scanned
each day that a patient is scanned, and for DXA
systems at least three times a week.
Inspection of QC results is carried out to
ensure they are within the accepted laid down
parameters, as any deviation on the QC reading
can invalidate or compromise patient results. In
the event that there is a deviation from the norm,
the phantom should be re-scanned three more
times and if it is still outside expected parameters,
scanning of patients should be discontinued
and the service company should be called out
to inspect the machine. The regular archiving of
hard copies of the QC results is also necessary for
the reason that inspection of these results may
be required, as part of record keeping and if site
inspection takes place by the RPII.
Like all equipment, DXA equipment requires
twice annual maintenance and budgeting for this
DXA centres should carry out a precision
study to determine its precision error and calculate the ‘least significant change’. This answers
the question about the significance of changes
between two sets of scans. The precision error
supplied by the manufacturer is not adequate in
this regard. If a DXA centre has more than one
operator, an average precision error, combining data from all operators should be used to
establish precision error and LSC for the centre,
provided the precision error for each operator
is within a pre-established range of acceptable
performance.
Every operator should do one complete
precision assessment after basic scanning skills
have been learned and after having performed
approximately 100 patient scans. Precision assessment should be standard clinical practice. n
Susan Vanderkamp is clinical nurse
specialist in osteoporosis, St Vincent’s
University Hospital, Dublin
pa ti en t
GP
pa ti ent
Sp ecia l i st
References
1. Nih Consensus Development Panel on Osteoporosis
Prevention D, Therapy. Osteoporosis Prevention, Diagnosis, and Therapy. JAMA 2001;285:785-95
2. Baim S, Binkley N, Bilzekian J, et al. Official positions
of the International Society for Clinical Densitometry and
executive summary of the 2007 ISCD Position Development Conference. J Clin Densitom 2008;11:75-91
3. Organization WH. Assessment of fracture risk and its
application to screening for postmenopausal osteoporosis. WHO Technical Report Series 843 WHO, Geneva
1994
4. Kanis J, Johnell O, Oden A, Johansson H, McCloskey
E. FRAXTM and the assessment of fracture probability in men and women from the UK. Osteoporos Int
2008;19:385-97
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