/ 161 Saudi Diploma in Family Medicine Center of Post Graduate Studies in Family Medicine EBM Therapy Articles Dr. Zekeriya Aktürk

/ 162 Case You are seeing a 34 y/o woman with recurrent migraine headaches 3-4 times per month. All attempts to prevent them have had minimal success. She heard some vitamin supplement may help. PICO: In women with frequent migraines unresponsive to usual therapies is there a vitamin that is more effective than placebo to decrease the frequency of migraine?

/ Determine Relevance Read the title and the conclusion of the abstract: 1.Did the authors study an outcome that patients would care about? 2.Is the problem studied one that is common to your practice and the intervention feasible? 3.Will this information, if true, require you to change your current practice?

/ Determine Validity Internal validity: How well was the study done? Do the results reflect the truth? –Level of Evidence? External validity: can I apply these results to MY patients?

/ Determine Validity Read the methods section –Answer questions on lower half of worksheet –Study design flaws are common, but are they “fatal”? “Stop” questions = fatal flaws

/ 166 Fatal Flaw #1 Was it a randomized controlled trial? Randomization is the best protection against being mislead

/ 167 Did investigators know to which group the potential subject would be assigned before enrolling them? Fatal Flaw #2 Was allocation assignment concealed?

/ 168 Are the study patients similar to yours? Addresses generalizability of results to your practice

/ 169 Patients: –Type 1 diabetes, years old –No Htn, chol, diabetic complications –Willing to check BS QID, inject insulin 3-4 times/day –Monthly visits for 6.5 years –Twice weekly phone follow-up x 6.5 years –Bajillion tests over 6.5 years Are these patients representative of type 2 diabetics seen in FP? –ADA uses these results to support tight glucose control in type 2 DM N Engl J Med 1993;329: Diabetes Complications and Control Trial

/ 1610 Were all the patients properly accounted for at its conclusion? Complete follow-up? “Intention to treat” analysis?

/ 1611 Was study “double-blinded”? Did the patients know to which group they were assigned? Did the treating physician know? Did investigators assessing outcomes know?

/ 1612 Were intervention and control groups similar? See Table 1 of most studies Randomization is best way to avoid bias, though imbalances still can occur (especially if allocation was not concealed) Small differences sometimes are important

/ 1613 Significance of Results? Statistical –general standard: p-value < 0.05 (5%) Was the power adequate? –power = ability of the study to find a difference IF one truly exists –general standard: power = 0.8 clinical vs. statistical significance

/ 1614 Study results AbbrevVariableEquationValue -subjects in control groupcontrol group-250 -subjects in experimental gr-150 -events in control group-100 -events in experimental group-15 CERcontrol event rate= events / subjects in control gr0.4, 40% EERexperimental event rate= events / subjects in exp. group0.1, 10% ARRabsolute risk reduction= CER – EER0.3, 30% RRRrelative risk reduction= (CER - EER) / CER0.75 NNTnumber needed to treat= 1 / ARR3.33 RRrelative risk= CER / EER4

/ 1615 Example A 10% of patients with disease A get complication if not treated If treated, complication decreases to 8% ARR=10-8=2% RRR=2/10=20% NNT=1/0.2=5 patients

/ 1616 Example B 1.5% of patients with disease B get complication if not treated If treated, complication rate decreases to 0.9% ARR= =0.6% RRR=0.6/1.5=40% NNT=1/0.006=167 patients