1. Describe a clinical scenario that you have recently encountered in
approximately 200 words
Finding a suitable clinical scenario can be a challenge. However on closer
inspection there are questions that you could ask about the diagnosis,
prognosis, aetiology and or treatment in the case of most patients that you
encounter.
In casualty you will be seeing patients at their pre diagnostic stage. Thus your
questions may be about diagnosis, differential diagnosis, first steps in
treatment, appropriateness of emergency management, positive and negative
predictive values of symptoms and signs for certain diagnoses etc.
If on the other hand you are working on a ward, the diagnosis has usually
been agreed and you are looking at patients in which the most important
issues are therapy, prognosis and causes (aetiology). Your questions may
therefore be about choosing between therapeutic alternatives (why do we use
this regime, is there an alternative? You may need to consider the evidence
supporting one diagnosis as opposed to another etc.
I have used a patient who presented in A/E at UCHG in early December
recently to illustrate what I mean by an evidence based case report. The
structure that I will use is the same one that I have given you on your
instruction sheet. I hope that this gives you a good idea of what is expected
of you. If you are still finding it difficult to find a suitable patient and/or choose
a question etc. e-mail your questions to the department of medical informatics
and medical education mime@nuigalway.ie . I am happy to help you to
choose patients, frame questions and to give you some advice on searching
The case that I chose was the following:
A 55 year old man was sent to casualty by his GP complaining of vague back
pain. The GP’s letter stated that the man had suffered from urinary hesitancy,
dribbling, double voiding etc. for some time. His Prostate Specific Antigen
was 46 and he had evidence of possible sclerotic lesions on a spinal x-ray.
The GP concluded that man had probable prostatic cancer with spinal
metastases. The patient was seen by the urology registrar who agreed with
the probable diagnoses. He ordered a bone scan, a repeat PSA test and
renal function tests. I wondered whether a prostate specific antigen of 46 was
predictive enough of metastatic spread. Was an expensive bone scan really
necessary?
(114 Words)
1. From this scenario create a structured question for which you
require an “evidence based” answer
To create a structured question you will need to identify what are the
questions that you want to look into about this patient’s case. Of these
questions which is the most pertinent, interesting etc.? Once you have
decided which question you want to use you then need to put that question
into a form that will allow you to find some answers. The best method is to try
to put the question into a structure that resembles the following:




The patient or problem
The intervention or therapy or prognostic factor or cause
A comparison intervention or cause (if there is one?)
An outcome that you want to know about
Here are some examples
Patient or problem
Intervention,
cause, prognostic
factor etc.
Comparison
intervention
Outcome
Starting with your
patient ask “how
would I describe a
group of patients
similar to mine.
Which intervention,
cause etc. am I
considering?
What is the main
alternative?
What do I/ we hope
to accomplish?
In patients who have
atrial fibrillation and
a dilated left
ventricle on ECHO
Does
anticoagulation with
warfarin
Compared with
standard A Fib.
Therapy alone
Reduce the rate of
thromboembolic
events e.g. stokes
Diagnosis question
In patients who
present with
symptoms and signs
suggestive of
appendicitis
Does a raised
neutrophil count on
an FBC test
Compared to a
normal neutrophil
count
Increase the
likelihood that the
patient has
appendicitis
Prognosis
question
In patients
undergoing lower
limb arterial bypass
surgery
Does a history of
previous myocardial
Infarct
Compared to
patients no with no
evidence of a
previous MI
Lead to a longer
recovery period or
greater incidence of
post-operative
complications etc.?
Tips: from Sackett et
al. See book
reference at the end
of this case report
Therapy question
My structured question is as follows:
In patients with suspected metastatic prostate cancer in whom the PSA is
>20mcg/L does the addition of radionucleotide bone scanning, compared
with PSA screening alone make a significant difference to the detection
of metastatic prostate cancer.
The key words that I thought might be useful for this search question are:




prostate specific antigen,
radionucleotide bone scan,
predictive value of tests,
diagnosis,
I tried a quick Medline search using these terms. I found one article that
covered the topic of PSA and Bone Scans. I looked at the “Complete
Reference” for the paper. It included a list of all the MeSH terms used to code
the article. I used some of these terms to add to my search term list:






Prostate-specific antigen/bl (blood test = bl)
Prostate neoplasms/bl
Prostate neoplasms/ri (radionucleotide investigation)
Predictive value of tests
Prognosis
Neoplasm staging/mt (metastatic)
I have put together a useful Internet search list for you. These sites
include Search engines, Databases, on-line journals etc. I strongly
recommend that you use Doctors Desk as a starting point as it links to
many on-line journals, the Cochrane Database, free Medline and
Bandolier. The list is available on the Q Drive and is labelled EBM
Toolbox
2. Study the abstracts of the studies that you have found and identify 5 key
papers that answer your question. Please ensure that these papers are
either available in full text on-line or that the relevant journal is held by the
Hardiman library. You will be required to submit the 5 full text papers with
your completed evidence based case study.
A list of all the journals held by the
Hardiman library can be found on
the library website.
The five papers used in this evidence based case report
a)
b)
c)
d)
e)
PSA and Bone Scans, Bandolier Vol.47 No. 4
Serum PSA predicts negative Bone Scan Bandolier Vol.2 No.4
Haukaas S., Roervik J., Halvorsen OJ, Foelling M. When is bone
scintigraphy necessary in the assessment of newly diagnosed
untreated prostate cancer; British Journal of Urology. Vol.79
(5):770-6, 1997
The positive yield of imaging studies in the evaluation of men with
newly diagnosed prostate cancer: a population based analysis.
Albertsen PC; Hanley JA; Gilliland FD; Hamilton A; Liff JM; Stanford
JL; Stephenson RA. The Journal of Urology Vol. 163 (4): 1138-43
Lin K; Szabo Z; Chin BB; Civelek AC; The value of a baseline bone
scan in patients with newly diagnosed prostate cancer. Clin Nuc
Med Vol. 24 (8): 579-82.
3. Give a brief description of each paper in terms of its
 study design
 methodology
 relevance to your question
 quality
Paper 1: PSA and Bone Scans
Study design
This is a review of a paper published in the British Journal Of Urology
Methodology
The paper summarises the findings from the original paper
Relevance to your question
This paper is included because it provides useful evidence supporting the
avoidance of bone scans in patients who have PSA levels < 20mcg/L
Quality
The paper is well presented, brief and accurately reports the findings of the
original paper
Paper 2: Serum PSA predicts negative Bone Scan
Study design
This is a report of a paper published in The Journal Of Urology
Methodology
The paper summarises the findings from the original paper
Relevance to your question
This paper is included because it provides a detailed description of the
original study findings. It explains that bone scans are expensive and
unpleasant. PSA alone is 99.7% predictive of the presence of Bone
metastases in prostatic cancer. The paper argues strongly for the
abandonment of bone scans in patients who’s PSA is <20
Quality
The paper is well presented, and reports the findings from an original paper.
It is important to check the original paper for any factual inaccuracies or
potential misinterpretations
Paper 3: When is bone scintigraphy necessary in the assessment of
newly diagnosed untreated prostate cancer
Study design
Cross sectional survey of 128 patients newly diagnosed with prostate cancer
comparing the prevalence of bone metastases at different levels of PSA.
Methodology
The authors measured PSA in men with newly diagnosed cancer. They then
did a bone scan on each patient. The correlated the bone scan findings with
the PSA scores. The authors then estimated the positive predictive value of
PSA for bone metastases at different values of PSA
Relevance to your question
This paper is included because it provides evidence that a PSA of < 20 is
predictive of the absence of bony metastases.
Quality
The study is well constructed, it has a small but reasonable number of
subjects and there are no obvious biasing factors
Paper 4: The positive yield of imaging studies in the evaluation of men
with newly diagnosed prostate cancer: a population based analysis.
Study design
Prospective survey of 3,690 patients newly diagnosed with prostate cancer
comparing the prevalence of bone metastases on Bone scan and CT scan at
different levels of PSA.
Methodology
The clinics involved in the study measured PSA in men with newly diagnosed
cancer. They then did a bone scan, a CT scan and in some cases and MRI
on each patient. The correlated the bone scan findings with the PSA scores.
The authors then estimated the positive yield of PSA in identifying bone
metastases at different values of PSA.
Relevance to your question
This paper is included because once again it provides evidence that a PSA of
< 20 is predictive of the absence of bony metastases.
Quality
The study is reasonably well constructed. It has a large number of subjects
and there are no obvious biasing factors. One weakness is that the authors
do not calculate a positive predictive value for the PSA but express their
results in terms of the correlation between PSA value and positive bone
scans. This is not as immediately useful a result as predictive value.
Paper 5: The value of a baseline bone scan in patients with newly
diagnosed prostate cancer.
Study design
Retrospective survey of the records of 270 patients with newly diagnosed with
prostate cancer
Methodology
The authors analysed the records of 270 men who had been diagnosed with
Prostate Cancer between 1995 and 1997. They correlated positive bone
scans with PSA measurements
Relevance to your question
This paper is included because it provides evidence that a PSA of < 10 is
predictive of the absence of bony metastases. The implication of the paper is
that metastatic spread might be missed in a few cases if the PSA threshold
was set at 20
Quality
The study is retrospective and is therefore open to record inaccuracies. The
authors did not explain whether the group of 270 was a sample taken from a
larger population or constituted all the patients attending one centre.
Nonetheless the results seem credible and could influence the PSA threshold
that is chosen for deciding about a bone scan.
4. Synthesise the findings from the 5 papers into an answer to the
clinical question that you set for yourself. (Answers should be
between 1000 and 2000 words long). Include a paragraph of your
conclusions.
The question that I set for myself has turned out to be a two stemmed query.
The first question is whether a PSA of 46 means that metastatic disease is
certain and a bone scan is unnecessary to confirm it. The second question is
whether it is safe not to do a bone scan in patients with a PSA of < 20.
From these 5 papers I can say that the PSA is better at ruling out (negative
predictive value) disseminated prostatic cancer than it is at diagnosing
prostatic metastatic disease1 If the PSA is < 10 the likelihood of having
disseminated cancer is < 0.5% 2 If the PSA is < 20 the likelihood of having
disseminated cancer rises to between 0.1 and 1.8%3 Thus it would be safe to
base a decision not to scan on the basis of a low PSA result (particularly if ,
< 10mcg/L)4,5. It is conversely not safe to assume that a PSA result > 20
implies that metastasis has taken place.
5. List the references to your 5 key papers in the order in which you
refer to them in the text of your case study using the Vancouver style
1.
PSA and Bone Scans, Bandolier Vol.47 No. 4
2.
Serum PSA predicts negative Bone Scan Bandolier Vol.2 No.4
3.
Haukaas S; Roervik J; Halvorsen OJ; Foelling M. When is bone
scintigraphy necessary in the assessment of newly diagnosed
untreated prostate cancer. British Journal of Urology. Vol.79 (5):770-6,
1997
4.
Albertsen PC; Hanley JA; Gilliland FD; Hamilton A; Liff JM; Stanford
JL; Stephenson RA The positive yield of imaging studies in the
evaluation of men with newly diagnosed prostate cancer: a population
based analysis. The Journal of Urology Vol. 163 (4): 1138-43
5.
Lin K; Szabo Z; Chin BB; Civelek AC; The value of a baseline bone
scan in patients with newly diagnosed prostate cancer. Clin Nuc Med
Vol. 24 (8): 579-82.
6. Submit your completed case study with copies of the 5 papers used
as evidence to Dr Cantillon at the Department of Medical Informatics
and Medical Education on or before the 28th of February 2001
Word count including references and excluding instructions is 1309