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How to appraise Medical Journal (Therapy) นพ.บริบรู ณ ์ เชนธนากิจ หน่วยเวชศาสตรฉุ ์ กเฉิน ภาควิชาเวชศาสตรครอบครั ว ์ คณะแพทยศาสตรมหาวิ ทยาลัยเชียงใหม่ ์ What is EBM? Patient Concerns EBM Best research evidence Clinical Expertise Critical appraisal Are the result valid? What are the results? How can I apply the result to patient care? Are the result valid? ประเด็นทีต ่ องประเมิ นวา่ RCT นั้นน่าจะมี BIAS ้ หรือไม่ • Did Intervention & Control groups start with same prognosis? • Was prognostic balanced maintained as the study progressed? • Were the groups prognostically balanced at the study’s complettion? Are the result valid? • Did Intervention & Control groups start with same prognosis? •Were patients randomized? •Was randomization concealed? •were patients similar in respect to known prognostic factor • Was prognostic balanced maintained as the study progressed? • Were the groups prognostically balanced at the study’s completion? THERAPY STUDY: Are the results of the trial valid? What question did Randomization the study ask? Patients – Intervention - Comparison - (Internal Validity) Outcome(s) - 1a. R- Was the assignment of patients to treatments randomised? What is best? Centralised computer randomisation is ideal and often used in multi-centred trials. Smaller trials may use an independent person (e.g, the hospital pharmacy) to “police” the randomization. This paper: Yes No Unclear Where do I find the information? The Methods should tell you how patients were allocated to groups and whether or not randomisation was concealed. Comment: 1b. R- Were the groups similar at the start of the trial? independent person (e.g, the hospital pharmacy) to “police” the randomization. This paper: Yes No Unclear Comment: concealed. Randomization 1b. R- Were the groups similar at the start of the trial? What is best? Where do I find the information? If the randomisation process worked (that is, achieved The Results should have a table of "Baseline comparable groups) the groups should be similar. The Characteristics" comparing the randomized groups on a more similar the groups the better it is. number of variables that could affect the outcome (ie. There should be some indication of whether dif ferences age, risk factors etc). If not, there may be a description of between groups are statistically significant (ie. p values). group similarity in the first paragraphs of the Results section. This paper: Yes No Unclear Comment: 2a. A – Aside from the allocated treatment, were groups treated Are the result valid? • Did Intervention & Control groups start with same prognosis? • Was prognostic balanced maintained as the study progressed? 1.To what extent was the study blinded? • Were the groups prognostically balanced at the study’s completion? results. Patients should also be analysed in the groups will need to read the results section to clarify the number to which they were randomised – ‘intention-to-treat and reason for losses to follow-up. analysis’. This paper: Yes No Unclear Comment: Blindness 3. M - Were measures objective or were the patients and clinicians kept “blind” to which treatment was being received? What is best? It is ideal if the study is ‘double-blinded’ – that is, both patients and investigators are unaware of treatment allocation. If the outcome is objective (eg., death) then blinding is less critical. If the outcome is subjective (eg., symptoms or function) then blinding of the outcome assessor is critical. This paper: Yes No Unclear Comment: Where do I find the information? First, look in the Methods section to see if there is some mention of masking of treatments, eg., placebos with the same appearance or sham therapy. Second, the Methods section should describe how the outcome was assessed and whether the assessor/s were aware of the patients' treatment. between groups are statistically significant (ie. p values). group similarity in the first paragraphs of the Results section. Co-intervention/Confounders This paper: Yes No Unclear Comment: 2a. A – Aside from the allocated treatment, were groups treated equally? What is best? Apart from the intervention the patients in the different groups should be treated the same, eg., additional treatments or tests. This paper: Yes No Unclear Comment: Where do I find the information? Look in the Methods section for the follow-up schedule, and permitted additional treatments, etc and in Results for actual use. 2b. A – Were all patients who entered the trial accounted for? – and Are the result valid? • Did Intervention & Control groups start with same prognosis? • Was prognostic balanced maintained as the study progressed? • Were the groups prognostically balanced at the study’s completion? • Was follow up complete? • Were patients analyzed in the group to which they were randomized? What is best? Apart from the intervention the patients in the dif ferent groups should be treated the same, eg., additional treatments or tests. This paper: Yes No Unclear Comment: Where do I find the information? Look in the Methods section for the follow-up schedule, and permitted additional treatments, etc and in Results for actual use. Intention to treat analysis 2b. A – Were all patients who entered the trial accounted for? – and were they analysed in the groups to which they were randomised? What is best? Where do I find the information? Losses to follow-up should be minimal – preferably less The Results section should say how many patients were than 20%. However, if few patients have the outcome of andomised (eg., Baseline Characteristics table) and how interest, then even small losses to follow-up can bias the many patients were actually included in the analysis. You results. Patients should also be analysed in the groups will need to read the results section to clarify the number to which they were randomised – ‘ intention-to-treat and reason for losses to follow-up. analysis’. This paper: Yes No Unclear Comment: 3. M - Were measures objective or were the patients and clinicians kept “blind” to which treatment was being received? What is best? Where do I find the information? Critical appraisal Are the result valid? What are the results? How can I apply the result to patient care? What are the result? • How large was the treatment effect? • How precise was the estimate of treatment effect? Critical Appraisal for Therapy Articles Treatment effect What were the results? 1. How large was the treatment effect? Most often results are presented as dichotomous outcomes (yes or not outcomes that happen or don't happen) and can include such outcomes as cancer recurrence, myocardial infarction and death. Consider a study in which 15% (0.15) of the control group died and 10% (0.10) of the treatment group died after 2 years of treatment. The results can be expressed in many ways as shown below . What is the measure? What does it mean? Relative Risk (RR) = risk of the outcome in the The relative risk tells us how many times more likely it is that treatment group / risk of the outcome in the control an event will occur in the treatment group relative to the control group. group. An RR of 1 means that there is no difference between the two groups thus, the treatment had no effect. An RR < 1 means that the treatment decreases the risk of the outcome. An RR > 1 means that the treatment increased the risk of the outcome. In our example, the RR = 0.10/0.15 = 0.67 Since the RR < 1, the treatment decreases the risk of death. Absolute Risk Reduction (ARR) = risk of the The absolute risk reduction tells us the absolute dif ference in outcome in the control group - risk of the outcome the rates of events between the two groups and gives an group. group. An(yes RR orof not 1 means that there is no difference between Most often results are presented as dichotomous outcomes outcomes that happen or don't happen) the myocardial two groups infarction thus, the treatment no effect. An RR <1 and can include such outcomes as cancer recurrence, and death.had Consider a study in which the treatment decreases the riskof oftreatment. the outcome. 15% (0.15) of the control group died and 10% (0.10)means of thethat treatment group died after 2 years The An RR > 1 means that the treatment increased the risk of the results can be expressed in many ways as shown below. outcome. InWhat our example, RR = 0.10/0.15 = 0.67 Since RR < it 1, the treatment decreases the risk of death. is thethemeasure? Whatthedoes mean? Absolute Risk(RR) Reduction = risk ofinthe risktells reduction us the absolute Relative Risk = risk of(ARR) the outcome the The absolute relative risk us howtells many times moredifference likely it is inthat outcome the control - risk of the outcome rates of the twogroup groupsrelative and gives treatmentingroup / risk ofgroup the outcome in the control the an event willevents occur between in the treatment to theancontrol ingroup. the treatment group. This is also known as the indication effect. Anbetween ARR of group. An ofRRtheof baseline 1 meansrisk thatand theretreatment is no difference absolute risk difference. 0themeans that there no difference between the twoAngroups two groups thus,isthe treatment had no effect. RR < 1 thus, treatment had nodecreases effect. the risk of the outcome. meansthethat the treatment In our example, the ARR = 0.15 - 0.10 = 0.05 or The absolute benefitthatofthe treatment is aincreased 5% reduction in the An RR > 1 means treatment the risk of the 5% death rate. outcome. Relative Risk Reduction (RRR) = absolute is the decreases complementtheofrisk the ofRRdeath. and is In our example, the RR = 0.10/0.15 = 0.67 risk The Sincerelative the RRrisk < 1,reduction the treatment reduction / risk of the outcome in the control probably the most commonly reported measure of treatment Absolute Risk Reduction (ARR) = risk of the The absolute risk reduction tells us the absolute difference in group. An alternative way to calculate the RRR is effects. It tells us the reduction in the rate of the outcome in the outcome in the control group - risk of the outcome the rates of events between the two groups and gives an to subtract the RR from 1 (eg. RRR = 1 - RR) treatment group relative to that in the control group. in the treatment group. This is also known as the indication of the baseline risk and treatment effect. An ARR of In our example, the RRR = 0.05/0.15 = 0.33 or The treatment reduced the risk of death by 33% relative to that absolute risk difference. 0 means that there is no difference between the two groups 33% occurring in the control group. thus, the treatment had no effect. Or RRR = 1 - 0.67 = 0.33 or 33% In our example, the ARR = 0.15 - 0.10 = 0.05 or The absolute benefit of treatment is a 5% reduction in the Number Needed to Treat (NNT) = inverse of the The number needed to treat represents the number of patients 5% death rate. Treatment effect Most often results are presented as dichotomous outcomes (yes or not outcomes that happen or don't happen) reduction / risk ofsuch the outcome controlrecurrence, probably the most commonly measurea ofstudy treatment and can include outcomesinasthecancer myocardial infarction and reported death. Consider in which group. An alternative way to calculate the RRR is effects. It tells us the reduction in the rate of the outcome in the 15% (0.15) of the control groupTreatment died and 10% (0.10) of the treatment group died after 2 years of treatment. The effect toresults subtract the RR from 1 (eg. RRR = 1 RR) treatment group relative to that in the control group. can be expressed in many ways as shown below. In our example, the RRR = 0.05/0.15 = 0.33 or The treatment reduced the risk of death by 33% relative to that 33% occurring in the control group. What is the measure? What does it mean? Or RRR = 1 - 0.67 = 0.33 or 33% Relative Needed Risk (RR)to =Treat risk of(NNT) the outcome The number relative risk tellstoustreat howrepresents many timesthemore likely it is that Number = inverseinofthethe The needed number of patients treatment / risk ofasthe1 /outcome an event occurwithin the the experimental treatment group relative to thetocontrol ARR and isgroup calculated ARR. in the control we need towilltreat therapy in order group. group. An1 bad RR outcome of 1 meansandthatincorporates there is nothedifference prevent durationbetween of the two groups the treatment no effect. An RR < 1 treatment. Clinicalthus,significance can had be determined to some meansbythatlooking the treatment decreases of the outcome. extent at the NNTs, but alsothebyriskweighing the NNTs An RR >any1 means the treatment risk of the against harms that or adverse effectsincreased (NNHs) ofthetherapy. outcome. In our example, the NNT = 1/ 0.05 = 20 We would need to treat 20 people for 2 years in order to In our example, the RR = 0.10/0.15 = 0.67 Since the1 death. RR < 1, the treatment decreases the risk of death. prevent Absolute Risk Reduction risk ofestimate the The of absolute reduction tellseffect? us the absolute difference in 1. How precise(ARR) was =the therisktreatment outcome in the control group risk of the outcome the rates of events between the two groups and gives an The true risk of the outcome in the population is not known and the best we can do is estimate the true risk based Critical appraisal Are the result valid? What are the results? How can I apply the result to patient care? Apply to patient care? • Were the study patients similar to my patient? • Were all clinically important outcomes considered? • Are the likely treatment benefits worth the potential harm and costs? “ขอซั ก ถาม” ้ สวัสดี 22