• / 52
  • 下载费用:50 金币  

NumberNeededtoTreatIM需要治疗的人数我

关 键 词:
Number Needed IM需要治疗的人数我 NumberNeededtoTreat IM需要治疗的人数
资源描述:
Number Needed to Treat Alex Djuricich, MD Indiana University School of Medicine Department of Medicine Ambulatory Rotation 2006-2007 Objectives • To learn basic information used in evaluating articles about therapy • To learn definitions of the following and be able to apply them to appraising articles on therapy: • CER (Control event rate) • EER (Experimental event rate) • RRR (Relative risk reduction) • ARR (Absolute risk reduction) • NNT (Number Needed to Treat) Objectives • To learn the “correlaries” to each of these definitions for harm • RRI (Relative risk increase) • ARI (Absolute risk increase) • NNH (Number needed to harm) Hypothetical trial • Trial of 1000 patients to compare use of MiGone (I made that one up? Like the name? Get it?) vs. placebo to prevent MI, given over 5 years. Patients for study are all healthy gym rats, coming from Bally’s Gym. Trial stats Total number of patients N=1000 Control group N=400 MiGone group N=600 # who developed an MI 2018 # who developed myalgias 412 For MI • CER • 20/400 = 0.05, or 5% • EER • 18/600 = 0.03, or 3% • ARR • 0.05 – 0.03 = 0.02, or 2% • RRR • (0.05 – 0.03)/0.05 = 0.02/0.05 = 40% For MI • NNT • 1/ARR • 1/0.02 = 50 • 50 patients would need to be treated to prevent one MI in 5 years in Bally’s Gym patients For myalgias • CER • 4/400 = 0.01, or 1% • EER • 12/600 = 0.02, or 2% • ARI • 0.02 – 0.01 = 0.01, or 1% • RRI • 0.02 – 0.01/0.01 = 0.01/0.01 = 1, or 100% For myalgias • NNH • 1/ARI • 1/0.01 = 100 • 100 patients would need to be treated with MiGone over 5 years to cause one case (harm) of myalgias Case #1 • You just completed your GI rotation, and are now doing Wishard wards. • You admit a 50 year old alcoholic gentleman for abdominal pain. After imaging, you find that he has radiologic “cirrhosis” with evidence of portal hypertension. He has NEVER had an upper GI bleed Case #1 continued • You discuss preventive pharmacologic treatments in rounds with the attending • In patient with cirrhosis and portal hypertension, does a non-selective beta blocker prevent gastroesophageal varices? • Yes • No Article • Beta-blockers to prevent gastroeophageal varices in patients with cirrhosis • Groszmann RJ, et al. New Engl J Med 2005;353:2254-61. Focus on Table #2 Total number of patients N=213 Control group N=105 Timolol group N=108 # who developed varices (%) 42 (40%)42 (39%) # who developed “Serious event” (buried on p.2258) 6 (5.7%)20 (18.5%) Control Event Rate • Percentage of those controls who develop the unwanted condition • In our example, varices or complication from it • 42/105 • 40% Experimental Event Rate • Percent of those in treatment group that developed the condition (varices) • 42/108 • 38.9% Absolute Risk Reduction • The true reduction in risk between control patients and treated patients • Difference between the CER and the EER • CER – EER • 0.4 – 0.389 • 0.011, or 1.1% • That’s ok, but not very impressive! Relative Risk Reduction • (CER – EER)/CER • (0.4 – 0.389)/0.4 • 0.011/0.4 • 0.0275, or 2.75% • Remember, 2.75% sounds better than 1.1%, but it still isn’t very “good” Number Needed to Treat (NNT) • Meaningful way of expressing benefit of an active treatment over a control • Defines treatment-specific event of an intervention NNT • Expression of the # of patients one would need to treat to prevent 1 additional adverse outcome (MI) or attain one additional benefit • 1/ARR • 1/0.011 • 91 (that is, 91 patients would need to be treated with timolol to prevent one additional case of varices) • Impressive? Not impressive? NNT • Function of 4 elements • ConditionCirrhosis pts • InterventionTimolol vs. placebo • Events being preventedVarices • Duration of follow-up55 months • Remember “DICE” NNT • Tells us in more concrete terms how much effort clinicians must expend to prevent one event, thus allowing comparisons with the amounts of efforts that must be expended to prevent the same or other events in patients with disorders NNT • Is a “good” NNT a low or a high number? • The lower the NNT, the larger the magnitude of treatment effect What about the “serious adverse events”? • Need to remember that medications have side effects, and that one can calculate how often we “harm” someone by giving a medication designed to help. • This “harm” is the side effect CER • For harm, the CER is still the same as before. • However, it applies to the harm instead of the “good” effect • In the example, it refers to “serious adverse events” (such as bradycardia) EER • This is really the same as before, except it applies to the rate for harm instead of for benefit • In our example, the EER is for “serious adverse events” ARI for “Harm” • Absolute Risk Increase • EER – CER • Note NOT “CER – EER” RRI • Relative Risk Increase • (EER – CER)/CER • Remember, its always the Control that goes in the denominator What about NNH? • In general, a decision to use therapy involves risk vs. benefit • Most therapies have side effects • Same concepts for NNT apply to side effects. We call that number the NNH (number needed to harm) NNH • The number of patients who, if they received the experimental treatment, would lead to one additional patient being “harmed”, compared with patients who received the comparison treatment. • 1/ARI Table #2 Again Total number of patients N=213 Control group N=105 Timolol group N=108 # who developed varices (%) 42 (40%)42 (39%) # who developed “Serious event” (buried on p.2258) 6 (5.7%)20 (18.5%) Let’s calculate for “serious adverse events” • CER • 6/105 (5.7%) • EER • 20/108 (18.5%) For “adverse events” • ARI • 18.5% - 5.7% = 12.8%, or 0.128 • RRI • (18.5% - 5.7%) / 5.7%= 224.5%, or 2.245 • NNH • 1/ARI • 1/0.128 • 7.8 (rounds to 8) patients need to be treated with timolol to cause one case of “serious adverse events” • This is unfortunately not a very good number; we want a very high NNH (as opposed to NNT) Case Take Home • According to this one study, the numbers are not impressive enough to recommend timolol to PREVENT varices in patients with diagnosed cirrhosis. • Remember that this is different from patients who have ALREADY had an upper GI bleed from varices secondary to cirrhosis. Those patients should get a beta blocker. Questions? Case #2 • You admit a patient on University Wards at night for bacterial meningitis. The ER doctor calls you with results of the CSF showing a WBC count of 1024, after noting cloudy CSF from the tap. She wants to know which antibiotic you would like to use; need an answer in 1 minute; meningitis is a true medical emergency!! • You recall from your pediatrics rotation about giving steroids in addition to antibiotics. • In patients with bacterial meningitis, does the use of concomitant dexamethasone improve neurological outcome? Example NEJM paper • Dexamethasone in adults with bacterial meningitis • deGans J, vandeBeek D, et al. New Engl J Med 2002;347:1549-56. • Total patients: 301 patients • 157 in dexamethasone (experimental) group • 144 in placebo (control) group NNT: Function of 4 elements • 1. Condition • meningitis • 2. Intervention • dexamethasone vs. placebo. Keep in mind that other treatments (antibiotics) were given to both groups, so placebo isn’t really “nothing” • 3. Events being prevented • unfavorable outcome (they define it), death • 4. Duration of follow-up • 8 weeks Dexamethasone paper Total # of patients N=301 Control group N=144 Dexamethasone group N=157 Unfavorable outcome 3623 Death2111 Dexamethasone paper • CER for unfavorable outcome • 36/144 • 0.25, or 25% • CER for death • 21/144 • 0.25, or 15% Dexamethasone paper • EER for unfavorable outcome • 23/157 • 0.15, or 15% • EER for death • 11/157 • 0.07, or 7% Dexamethasone paper • ARR for unfavorable outcome • CER – EER • 0.25 – 0.15 • 0.10, or 10% • ARR for death • CER – EER • 0.15 – 0.07 • 0.08, or 8% Dexamethasone paper • NNT for unfavorable outcome • 1/ARR • 1/0.10 • 10. You would need to treat 10 meningitis patients with dexamethasone to prevent one patient getting an “unfavorable outcome” after 8 weeks • NNT for death • 1/ARR • 1/0.08 • 12.5 (rounds up to 13). You would need to treat 13 meningitis patients with dexamethasone to prevent one death after 8 weeks Dexamethasone • How about NNH? • Calculate it for each of the “side effects” you are interested in. Dexamethasone paper Total # of patients Control group N=144 Dexamethasone group N=157 Hyperglycemia3750 Fungal infection48 Dexamethasone paper • CER for hyperglycemia • 37/144 • 0.26, or 26% • CER for fungal infection • 4/144 • 0.03, or 3% Dexamethasone paper • EER for hyperglycemia • 50/157 • 0.32, or 32% • EER for fungal infection • 8/157 • 0.05, or 5% Dexamethasone paper • ARI for hyperglycemia • EER – CER • 0.32 – 0.26 • 0.06, or 6% • ARI for fungal infection • EER – CER • 0.05 – 0.03 • 0.02, or 2% Dexamethasone paper • NNH for hyperglycemia • 1/ARI for hyperglycemia • 1/0.06 • 16.7 (rounds to 17) • You would need to treat 17 patients with bacterial meningitis to cause one case of hyperglycemia over 8 weeks Dexamethasone paper • NNH for fungal infection • 1/ARI for fungal infection • 1/0.02 • 50 • You would need to treat 50 patients with meningitis with dexamethasone to cause one case of fungal infection over 8 weeks Case Take Home • Consider steroids at the time of diagnosis of suspected meningitis. • They clearly have a role in improving outcomes, but this comes at a cost of increased fungal infection • Is it worth the risk? That is the “art” of medicine. Summary • CER (control event rate) • EER (experimental event rate) • ARR (absolute risk reduction) and ARI • RRR (relative risk reduction) and RRI • NNT (number needed to treat) • NNH (number needed to harm) Summary • NNT: Expression of # of patients one would need to treat to prevent one additional adverse outcome or attain one additional benefit • NNT is a function of: • Condition • Intervention • Events being prevented • Duration of follow-up • Remember, “DICE”
展开阅读全文
  麦档网所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
0条评论

还可以输入200字符

暂无评论,赶快抢占沙发吧。

关于本文
本文标题:NumberNeededtoTreatIM需要治疗的人数我
链接地址:https://www.maidoc.com/p-15679786.html
关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服 - 联系我们

copyright@ 2018-2020 maidoc.com版权所有  文库上传用户QQ群:3303921 

麦档网为“文档C2C模式”,即用户上传的文档所得金币直接给(下载)用户,本站只是中间服务平台,本站所有文档下载所得的金币归上传人(含作者)所有。
备案号:蜀ICP备17040478号-3  
川公网安备:51019002001290号 


收起
展开