The lecture explains the steps of thinking while applying the principles of evidence based medicine on radiology.An example from real life is given and how to apply this type of thinking in order to achieve the best results.

1. Talking “Evidence based
Radiology “
Dr/Ahmed Bahnassy
Consultant Radiologist

2. Time :Thursday at mid night
• Obese old primigravida ,diabetic ,16
weeks gestation(post artificial
insemination and follicular
stimulation),presenting to A&E with severe
abdominal pain (Right lower quadrant).
• Leucocytic count is borderline .
• The physician is stuck and asking for your
help …

3. Eminence-based vs. Evidence-
based Radiology
• “Eminence-based radiology” = based on
the belief that an expert with a practice
devoted to a particular discipline can amass
sufficient experience to determine the best
approach to clinical imaging problems
• “Evidence-based radiology” = based on the
understanding that an individual's experience
is biased by practice mix, overemphasis of
more recent events, small sample size, and
lack of objectivity
• Accordingly, best practice should be based
on well-designed and well-performed medical
research

4. Other types of medicine ?!
• Private based medicine ..
• Medicolegal based
medicine.
• Elusive based medicine .

5. What is Evidence-Based Medicine?
“Evidence-Based Medicine is the integration of best
research evidence with clinical expertise and patient
values”.
Dave Sackett Patient
Concerns • Obese.
• Old primi
EBM • After costly
Best research Clinical
evidence Expertise intervention.
• Second
trimester.

6. Definition of EBM:-
It is the process of systematically
reviewing, appraising and using
clinical research findings to aid
the delivery of optimum clinical
care to patients
Rosenberg W, Donald A. BMJ 1995; 310: 1122–1126

7. SO,
The practice of
Evidence-Based
Medicine is a
process of lifelong,
self-directed,
problem-based
learning.

8. The history of EBM:-
• In 1972 Professor Archie Cochrane a British
epidemiologist ,, expressed what later came to be
known as evidence-based medicine (EBM).
• Cochrane proposed that all the best clinical trials
should be systematically reviewed, specialty by
specialty. This lead to the development of the
Cochrane Library of Systematic Reviews.
• These concepts were developed into a practical
methodology by groups working at Duke University in
North Carolina and McMaster University in Toronto in
the late 1980s and early 1990s.

9. The history of EBM (Cont.):-
• In 1992, the UK government funded the establishment
of the Cochrane Centre in Oxford, with the objective
to facilitate the preparation of systematic reviews of
randomised controlled trials of healthcare.
• The following year it expanded into an international
collaboration of centers, whose role is to co-ordinate
the activities of thousands of researchers.
• JAMA 1992; 268: 2420–2425.
• Eddy DM. JAMA 1990; 263: 1265, 1269, 1272 passim.
• Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. BMJ 1996; 312: 71–72.

10. What is Evidence based Radiology
• It is important for radiologists
to realize that EBR offers
solution that can be applied at
many levels of professional
involvement.
• A unique feature of EBR is that
it can be used readily by
practicing radiologists working
at the effectiveness level:
performance in their own
departments under ordinary,
rather than ideal conditions.

11. How to practice EBM?
EBM practice requires 5 As:
• Asking
• Acquiring
• Appraising
• Applying
• Assessing
Sharon E. Straus

12. The 5 As
• Ask clinical question:
convert information needs into a clearly defined
answerable question,
• Acquire the evidence:
conduct a systematic search for the best available
evidence for the problem,
• Appraise the evidence:
evaluate the validity and applicability of the evidence,
• Apply the evidence:
prepare synthesis or summary of the evidence for
decision making and implement in practice,
• Assess your performance.

13. 1. Ask clinical question
What makes a clinical question well built?
Phrase the question for a precise answer.
To achieve this, formulate an answerable question, including:
• Population or disease state
• Intervention
• Comparison
• Outcome

15. PICO/PIO
• Population/Patients: pregnant women in
abdominal pain
• Intervention: Imaging
• Comparison: none (PIO )
• Outcome(s): accuracy of imaging modalities.

16. Another formulation
In pregnant women suffering of abdominal
pain ,what is the comparative value of
ultrasound ,CT and MRI .. findings ..?
‘Answerable questions are the backbone of practicing EBM’

17. Radiological considerations
• Obesity.
• Precious baby ..radiation concern.
• Accurate diagnosis.
• Available equipments .

18. How to search
• For primary sources, the free sites used by
most people are PubMed (available at: www
.ncbi.nlm.nih.gov/Pubmed; and Grateful Med (available at:
igm.nlm.nih.gov.
• Subscription-based search programs include
Ovid (available at: www.ovid.com; and Silver Platter (available
at: www.silverplatter.com;
• Radiology journals online
include the RSNA Index to Imaging Literature
(available at: rsnaindex.rsnajnls.org;
• Radiology Online (available
at: radiology.rsnajnls.org;
and the American Journal of
Roentgenology (www.ajr.com )

19. Start up
• Start Explorer and enter
– www.pubmed.gov
• Put on CAPS lock
– So that AND and OR are in CAPITALS

20. Abstracts Vs full text .
• Print single most relevant abstract for
each question – for both ‘set’ questions
and your own questions.
• Full text articles can also be
downloaded from pubmed or ovid
(radiographics ,Radiology ,AJR ..rarely
BJR …)

21. 3- Appraise the evidence (Critical appraisal):
This is a method of assessing and
interpreting the evidence by
systematically considering its
validity, results and relevance to the
area of work considered, and
classify it according to the
strength of evidence.

23. Levels of evidence in Radiology
(simplified)

24. Hierarchical Model of Efficacy
.

26. • Sensitivity • Specificity
• Ability to detect • Ability to identify
disease absence of disease.
• number of corective • Probability of having
+ve/number with –ve test given no
disease. disease.
• TP/D+ • TN/D-

27. Is the test helpful (valid)?
The Youden Index
• Youden Index = sensitivity+specificity-1
– For a test to be useful, then
• sensitivity + specificity - 1 (Youden Index > 0)
• Examples:
– Coin Toss with +ve = "heads"
sensitivity = 0.5 specificity = 0.5
– Youden = 0

28. • PPV • NPV
• Possibility of +ve test • Possibility of –ve test
to identify presence of to identify absence of
disease. disease.
• Correct +ve/Number • TN/T-
of positive tests.
• T+ve/T+

29. Likelihood Ratios//LR+..LR-
LRpos = sensitivity/( 1 - specificity)
LRneg = (1- sensitivity)/specificity.
A positive likelihood ratio greater
than 10 and a negative likelihood ratio
less than 0.1 provide “convincing” diagnostic evidence;
while
a positive likelihood ratio greater than 5 and a negative
likelihood ratio less than 0.2 provide “strong” diagnostic
evidence

30. Can a test rule-in or rule-out?
• SpPln
– Specific test, Positive rules In
eg: Rovsing's sign, ST elevation > 2mm
• SnNout
– Sensitive test, Negative rules Out
eg: Erect abdominal film for obstruction,

31. EBM and Systematic Review
• EBM (quick ) • Systematic Review
• Steps
– Answerable Question
• Steps
– Search – Answerable Question
– Appraise – Search ++++
– Appraise
– Apply – Synthesize
– Apply
• Time: 90 seconds
• < 20 articles. • Time: 6 months
• < 2,000 articles

32. What is a meta-analysis?
Optional part of a systematic review
Systematic reviews
Meta-analyses

35. The following is concluded after
appraisal of litterature.
In an initial series of 42 pregnant patients in
whom US was used for detection of acute
appendicitis:
100% sensitivity, 96% specificity, and
98% accuracy were reported.
Another study of 22 pregnant patients (all in
the first and second trimesters) reported
66% sensitivity and 95% specificity .

36. • Despite the variable sensitivity, US is still
recommended as a first-line test..
• lack of radiation ,alternative diagnosis
,etc…

37. • A very recent series included 51
pregnant patients
• suspected to have appendicitis .
• MR imaging had an overall
sensitivity
• of 100%, specificity of 93.6%, and
accuracy of 94%. (what is the
protocol )
• The authors concluded that MR
imaging should be used to
exclude acute appendicitis in
pregnant women suspected to
have appendicitis but with
inconclusive US results.
Pedrosa I, Zeikus EA, Levine D, Rofsky NM.
MR imaging of acute right lower quadrant pain in
pregnant and nopregnant patients. RadioGraphics
2007;27:721–753.

38. • A very recent retrospective study comprising
• 78 pregnant women with abdominal pain reported
• a 92% sensitivity, 99% specificity, and
• 99% negative predictive value of abdominal and
• pelvic CT for the diagnosis of appendicitis .
• Therefore, if MR imaging cannot be performed
• (contraindicated or not available), CT of the abdomen
• and pelvis should be used as a second-line
• test.

39. • encourage more avid efforts to keep the
radiation dose as low as possible (eg, by
decreasing the milliampere-seconds
value, using z-axis modulation, and
increasing the pitch )
the risk of malformations is
significantly increased above control
levels at doses above 15 rad (0.15
Gy)

40. What about Contrast Material ?
• Iodinated Contrast:
– Category B drugs; that is, animal reproduction
studies have not demonstrated a fetal risk,
• Gadolinium Contrast
– Animal studies show growth retardation and
congenital anomalies with doses 2-7x normal
human dose

41. The final answer
• I will begin by US ….if equivocal we will
arrange MRI abdomen.
• If contraindications to MRI exam…or MRI
unavailble ..
• we will arrange CT (sit with CT tec …to
decrease milli amp..Kvp..increase pitch…
modulate Z axis…use barium to decrease
fetal exposure )

43. MRI findings in acute appendicitis

44. Catarrhal appendicitis

45. Appendiceal phlegmon.

46. Examples of daily questions..!
• Pregnant lady with chest
pain..discomfort ..etc….is it pulmonary
embolism ?.
• Pregnant lady with trauma (RTA)?
• Old patient ..post cardiac surgery …Is it
bowel ischaemia ..?
• Intestinal obstruction…