Talking evidence based radiology


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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.

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  • Sackett DL, Rosenberg WMC, Gray JAM, Haynes RB, Richardson WS: Evidence based medicine: what it is and what it isn’t. BMJ 1996;312:71-2. This definition of what EBM is and isn’t has gained wide acceptance and made it easier for us to get our points across.
  • Meta analysis may be part of a systematic review. May be worth asking participants for egs of when it’s not appropriate to combine studies in meta-analysis. Systematic reviews may included meta-analyses but meta-analysis may be done with out systematically reviewing the studies – there are egs of this in journals – these therefore may be biased In the US the terms are used interchangably, but not the case in the UK
  • Talking evidence based radiology

    1. 1. Talking “Evidence based Radiology “ Dr/Ahmed Bahnassy Consultant Radiologist
    2. 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. 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 individuals 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. 4. Other types of medicine ?!• Private based medicine ..• Medicolegal based medicine.• Elusive based medicine .
    5. 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. 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 patientsRosenberg W, Donald A. BMJ 1995; 310: 1122–1126
    7. 7. SO, The practice of Evidence-Based Medicine is a process of lifelong, self-directed, problem-based learning.
    8. 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. 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. 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. 11. How to practice EBM?EBM practice requires 5 As:• Asking• Acquiring• Appraising• Applying• AssessingSharon E. Straus
    12. 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. 13. 1. Ask clinical questionWhat 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
    14. 14. PICO/PIO• Population/Patients: pregnant women in abdominal pain• Intervention: Imaging• Comparison: none (PIO )• Outcome(s): accuracy of imaging modalities.
    15. 15. Another formulationIn 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’
    16. 16. Radiological considerations• Obesity.• Precious baby ..radiation concern.• Accurate diagnosis.• Available equipments .
    17. 17. How to search• For primary sources, the free sites used bymost people are PubMed (available at:; and Grateful Med (available• Subscription-based search programs includeOvid (available at:; and Silver Platter (availableat:;• Radiology journals onlineinclude the RSNA Index to Imaging Literature(available at:;• Radiology Online (availableat:;and the American Journal ofRoentgenology ( )
    18. 18. Start up• Start Explorer and enter –• Put on CAPS lock – So that AND and OR are in CAPITALS
    19. 19. 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 …)
    20. 20. 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 thestrength of evidence.
    21. 21. Levels of evidence in Radiology (simplified)
    22. 22. Hierarchical Model of Efficacy .
    23. 23. • 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-
    24. 24. 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
    25. 25. • 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+
    26. 26. 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; whilea positive likelihood ratio greater than 5 and a negativelikelihood ratio less than 0.2 provide “strong” diagnosticevidence
    27. 27. Can a test rule-in or rule-out?• SpPln – Specific test, Positive rules In eg: Rovsings sign, ST elevation > 2mm• SnNout – Sensitive test, Negative rules Out eg: Erect abdominal film for obstruction,
    28. 28. 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
    29. 29. What is a meta-analysis?Optional part of a systematic review Systematic reviews Meta-analyses
    30. 30. The following is concluded after appraisal of litterature.In an initial series of 42 pregnant patients inwhom US was used for detection of acute appendicitis:100% sensitivity, 96% specificity, and98% accuracy were reported.Another study of 22 pregnant patients (all in the first and second trimesters) reported 66% sensitivity and 95% specificity .
    31. 31. • Despite the variable sensitivity, US is still recommended as a first-line test..• lack of radiation ,alternative diagnosis ,etc…
    32. 32. • 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.
    33. 33. • 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.
    34. 34. • 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)
    35. 35. 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
    36. 36. 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 )
    37. 37. MRI findings in acute appendicitis
    38. 38. Catarrhal appendicitis
    39. 39. Appendiceal phlegmon.
    40. 40. Examples of daily questions..!• Pregnant lady with chest pain..discomfort ..etc….is it pulmonary embolism ?.• Pregnant lady with trauma (RTA)?• Old patient cardiac surgery …Is it bowel ischaemia ..?• Intestinal obstruction…