Critical AppraisalArticles about

Therapy or Prevention

Jeffrey P Schaefer MSc MD FRCPC

March 26, 2007

Objectives

• After this session…– know where Critical Appraisal fits within the

Evidence Based Medicine Paradigm

– know how to Critically Appraise Articles about Therapy or Prevention using the McMaster Protocol (JAMA)

What’s Evidence Based Medicine?

What’s EBM?• Evidence-based medicine is the

conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.

• DL Sackett BMJ 1996; 312: 71-2

Best Available EvidencePhysician Experiences

Patient ValuesSystem Values

Evidence Based Medicine• Generate the Clinical Question

– harm, diagnosis, therapy, prognosis, prevention

• Find Answers– unfiltered sources –> Medline– filtered sources -> Uptodate

• Critically Appraise the Answers– assess Validity, Results, Applicability

• Apply the Evidence– patient, physician, system values

Hierarchy of Evidence:Therapy or Prevention

• N of 1 randomized controlled trial

• Systematic reviews of RCTs

• A single RCT

• Systematic review of observational

studies

• Physiological studies

• Unsystematic clinical observations

Critical Appraisal

Background

• Diabetes is prevalent

• Diabetes is associated with complications

• Rosiglitazone does good things with diabetes

• Can rosiglitazone prevent diabetes?

Methods

• Design– multicentre (191 sites, 21 countries)– randomized– matching placebo controlled– concealed

Methods

• Entry– 30 years or older– impaired glucose tolerance and/or– impaired fasting glucose

– exclude: diabetes (except gest), h/o cv disease, intolerance to ACE or TZD

Methods

• Intervention– rosiglitazone 4 mg od x 2 mo then 8 mg od– placebo

– Notes:• (factorial design with ramipril 15 mg od)• all received lifestyle couseling

Methods - Outcomes• Primary

– incident diabetes or all-cause death

• Secondary– regression to normal fasting and 2 hr OGTT– composite and indivudual: CV events– composite individual: cardiorenal events

• Other– ALT, ECG, waist & hip circumference, ECG

• Measurements: at 2 months, then q 6 months

Results

Secondary and Subgroups

• How much should we care?

• Subgroup analysis

Author’s Conclusions

• Addition of rosiglitazone to lifestyle … reduces the risk of developing diabetes by two-thirds

• NNT 1000 people, 3 years 144 cases

• Rosiglitazone treats dysglycemia

Critical Appraisal