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Where is the evidence? PHRM2010 Judith Coombes The University of Queensland/Princess Alexandra Hospital.

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Presentation on theme: "Where is the evidence? PHRM2010 Judith Coombes The University of Queensland/Princess Alexandra Hospital."— Presentation transcript:

1 Where is the evidence? PHRM2010 Judith Coombes The University of Queensland/Princess Alexandra Hospital

2 What is evidence based medicine? l Evidence-based medicine(EBM) is the integration of best research evidence with clinical expertise and patient values (Sackett et al 1999 )

3 A model of Evidence Based decisions Patient ValuesClinical Expertise Best research evidence Decision

4 Realisations l Daily need for valid up to date information l Inadequacy of traditional resources l Gap between clinical judgment which  over time while up to date theoretical knowledge  over time l Time limitation for finding evidence

5 FIVE steps l Convert information needs into an answerable question l Find the best evidence l Appraise validity, impact and applicability l Integrate appraisal with clinical expertise l Evaluate performance

6 Answerable question l The patient- 73 yr old female l main intervention-clopidogrel l comparison treatment-aspirin l clinical outcome-reduce mortality

7

8 Does an intervention work? l Case reports l Clinical experience l Case series l Case control study l Cohort study l Randomised, placebo controlled clinical study

9 FIVE steps l Convert information needs into an answerable question l Find the best evidence l Appraise validity, impact and applicability l Integrate appraisal with clinical expertise l Evaluate performance

10 Find the best evidence l Merck Manual says Aspirin mg no mention of clopidogrel l Cochrane database-1 review 2000 (amendment 2005) significant benefit but ? size l Clinical Evidence (BMJ) viewed uses cochrane 2005 review says doubtful benefit l Medline-pubmed 66 clinical trials in English » CAPRIE significant difference »CHARISMA clopidogrel plus aspirin

11 Implications for practice l The cost of treating 100 patients for two years with clopidogrel, at about US$800 per patient per year, totals about $160,000 to prevent one vascular event. As this is likely to exceed the average cost of the vascular event prevented, it seems prudent, at this stage at least, to infer that thienopyridines should not replace aspirin as the first choice antiplatelet agent for all high vascular risk patients. However, clopidogrel would seem to have a role for patients who are intolerant of, or allergic to, aspirin, provided we accept the caveat that we do not have direct evidence of the relative effectiveness of thienopyridines compared with aspirin in these patients because they were excluded from the randomised trials.

12 Developments l Strategies for finding and appraising evidence l Systematic reviews-Cochrane Collaboration l Evidence-based journals l Information systems bring info in seconds l Effective strategies for lifelong learning and improving clinical performance l EBM as a teaching/learning tool

13 Systematic reviews l Different to conventional narrative reviews l Very useful way of presenting the accumulated results from primary research l Systematic approach used to minimise bias and random errors

14 Why do we need systematic reviews of the evidence? l No-one can possibly read, or find, all the trials and all the data about all specific clinical questions l Once found, trials may appear to give conflicting or contradictory results

15 Cochrane Collaboration LOGO

16 Strength of evidence

17 How to obtain access to systematic reviews l Internet sites »eg. »www.cebm.utoronto.cawww.cebm.utoronto.ca l The Australasian Cochrane Centre - Flinders University, SA »www.cochrane.org.auwww.cochrane.org.au Evidence Based Guidelines NPS (Aus) and NICE (UK) National Prescribing service NPS National Institute of Clinical Excellence

18 FIVE steps l Convert information needs into an answerable question l Find the best evidence l Appraise validity, impact and applicability l Integrate appraisal with clinical expertise l Evaluate performance

19 Now we have found some evidence. Can we apply the evidence to this case ? l Validity l Impact l applicability

20 Is the systematic review valid? l Is the review of randomised trials l do the methods describe- »finding and including all relevant trials »how validity of individual trials was assessed l were the results consistent from study to study

21 Validity (CAPRIE) Was the assignment of patients to treatments randomised? YES Was the randomisation list concealed? YES Was follow-up of patients sufficiently long and complete? 1.91 yrs Were all patients analysed in the groups to which they were randomised? Yes Were patients and clinicians kept “blind” to treatment? Yes Were the groups treated equally, apart from the experimental treatment? YES Were the groups similar at the start of the trial? YES

22 Impact l Calculate the absolute benefit (or risk reduction) l Now the number needed treat (NNT) and for how long l calculate the absolute risk of harm

23 Impact Clopidogrel versus Aspirin Outcomes MI, STROKE, or vascular death combined After 1 year Relative risk reduction (RRR) Absolute risk reduction (ARR) Number needed to treat (NNT) CEREERCER – EER CER CER-EER 1 ARR 5.83%5.32%8.7%0.51%200

24 Applicability l How is our patient different from the study patient – previous stroke subgroup didn’t do as well, 72% men mean age 62.5 yrs l Is this a treatment the patient will form a partnership with us to follow- WILL IT BE SUBSIDISED- it costs much more

25 eTG l For initial antiplatelet therapy, aspirin alone or the combination of aspirin plus dipyridamole (modified- release) are acceptable options: l aspirin 100 to 300 mg orally, daily (although doses down to 30 mg daily may be adequate) aspirin l OR l dipyridamole (modified-release)+aspirin mg orally, twice daily. [Note 1] dipyridamoleaspirinNote 1 l l Due to enhanced efficacy, the combination of dipyridamole+aspirin is preferred in patients with moderate or greater absolute risk of recurrent stroke events. It should also be considered in patients with recurrent stroke events despite aspirin therapy. l Headache is the most frequent adverse effect with combination therapy and may be overcome by initiating treatment with smaller doses. l Dipyridamole alone may be used in patients intolerant of both aspirin and clopidogrel

26 eTG l Clopidogrel, a platelet aggregation inhibitor, was shown in the CAPRIE trial to be modestly more effective than aspirin in the prevention of serious high-risk vascular outcomes (stroke, myocardial infarction, vascular death). This trial showed a relative risk reduction of 8.7% for clopidogrel over aspirin, with a similar magnitude of risk reduction seen for the outcome of stroke alone (7.3%). However, because of the small absolute risk reduction (approximately 0.5% per year) and the cost of the drug, clopidogrel is mainly used as second-line therapy in patients who are either intolerant of aspirin (eg those with gastrointestinal bleeding) or have developed recurrent cerebral ischaemic events while on aspirin (so-called aspirin failures). For such patients, use: l clopidogrel 75 mg orally, daily (blood monitoring is not necessary). clopidogrel l More recently, clopidigrel has been tested in two clinical trials in combination with aspirin. The MATCH trial tested the addition of aspirin 75 mg daily to baseline clopidogrel in a stroke or TIA population comprising a high proportion of patients with small-vessel stroke syndromes associated with hypertension and diabetes. The addition of aspirin to clopidogrel did not significantly reduce the risk of the primary endpoint (a composite of ischaemic stroke, myocardial infarction, vascular death or rehospitalisation for acute ischaemia), but did result in significantly more life-threatening bleeds (2.6% versus 1.3%). The CHARISMA study tested the addition of clopidogrel 75 mg to baseline low-dose aspirin (75 to 162 mg) in two study populations—a ‘high-risk’ primary prevention group and a secondary prevention group combining patients with cardiovascular, cerebrovascular (approximately 35% of patients) and peripheral arterial disease. Overall there was no reduction in the primary end point of stroke, myocardial infarction or vascular death. Therefore, clopidogrel plus aspirin should not be used for long-term preventive therapy in patients with cerebrovascular disease.

27 Relevance of evidence based medicine to pharmacists l All areas of practice require decisions about optimal therapy (including no therapy) to improve patient outcomes l Information often comes to the pharmacist in an incomplete fashion l Pharmacists giving advice and being proactive in therapeutics need accurate information sources

28 Some limitations of evidence based medicine l Many questions do not have answers! l Evidence from populations - ?relevance to individual l Trials - not ‘real’ usage l Lack of local ownership of recommendations l Clinical effectiveness vs cost effectiveness

29 Combined approaches l Evidence based l Consensus l Local guidelines l Pharmacists can act as a focal or facilitation point

30 Summary l Evidence based medicine is an effective tool to maximise optimal outcomes for our patients l Pharmacists need to learn how to incorporate evidence based principles in their practice l Pharmacists can contribute to local implementation of evidence based guidelines


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