WordNet

give numbers to; "You should number the pages of the thesis"
place a limit on the number of (同)keep_down
a concept of quantity involving zero and units; "every number has a unique position in the sequence"
the property possessed by a sum or total or indefinite quantity of units or individuals; "he had a number of chores to do"; "the number of parameters is small"; "the figure was about a thousand" (同)figure
a clothing measurement; "a number 13 shoe"
an item of merchandise offered for sale; "she preferred the black nylon number"; "this sweater is an all-wool number"
a numeral or string of numerals that is used for identification; "she refused to give them her Social Security number" (同)identification number
a select company of people; "I hope to become one of their number before I die"
the grammatical category for the forms of nouns and pronouns and verbs that are used depending on the number of entities involved (singular or dual or plural); "in English the subject and the verb must agree in number"
enumerate; "We must number the names of the great mathematicians" (同)list
regard or consider in a specific way; "I treated his advances as a joke"
provide treatment for; "The doctor treated my broken leg"; "The nurses cared for the bomb victims"; "The patient must be treated right away or she will die"; "Treat the infection with antibiotics" (同)care_for
an occurrence that causes special pleasure or delight
interact in a certain way; "Do right by her"; "Treat him with caution, please"; "Handle the press reporters gently" (同)handle, do by
engage in negotiations in order to reach an agreement; "they had to treat with the King"
provide with a gift or entertainment; "Grandmother always treated us to the circus"; "I like to treat myself to a day at a spa when I am depressed"
have or feel a need for; "always needing friends and money"
a condition requiring relief; "she satisfied his need for affection"; "God has no need of men to accomplish His work"; "there is a demand for jobs" (同)demand
anything that is necessary but lacking; "he had sufficient means to meet his simple needs"; "I tried to supply his wants" (同)want
so frightened as to be unable to move; stunned or paralyzed with terror; petrified; "too numb with fear to move"
make numb or insensitive; "The shock numbed her senses" (同)benumb, blunt, dull

PrepTutorEJDIC

〈U〉〈C〉(数えて得られる)『数,数量』 / 〈C〉(概念としての)『数,数字』 / 〈C〉『番号』 / 〈C〉(演奏会や演劇の)番組,出し物;曲目 / 〈C〉(雑誌の)号 / 〈U〉(文法で)数(すう) / 《複数形で》数の上の優勢 / 《複数形で》算数 / 〈C〉《単数形で》《話》(商品としての)洋服の1点;商品,売り物 / 〈C〉《単随形で》《俗》女の子 / …‘を'数える / (…の中に,…として)…‘を'含める,加える《+『among』(『with, as』)+『名』》 / …‘に'番号をつける / …‘の'数となる / 《しばしば受動態で》…‘の'数を制限する / 総計(…に)なる《+『in』+『名』〈数〉》
《様態を表す副詞[句]を伴って》〈人・動物など〉‘を'『扱う』,待遇する・(…と)…‘を'『見なす』 (regard)《+名+as+名(形)》・〈問題など〉‘を'『扱う』,論じる・〈病人・病気など〉‘を'『治療する』,処理する・(化学薬品などで)…を処理する《+名+with+名》・(…を)〈人〉におごる,ごちそうする《+名〈人〉+to+名》・〈本・講義などが〉(問題などを)『扱う』,論じる《+of+名》・『おごる』,勘定をもつ・《文》(妥結・和解のために)(…と)交渉する,談判する《+with+名》・(思いがけなく)喜び(楽しみ)を与えてくれるもの・(めったにない)楽しみ・《one's treat》おごること,おごる番
〈U〉《時にa~》『必要』,入用 / 〈C〉《しばしば複数形で》『必要なもの』,(…の)必要品《+『for』+『名』》 / 〈C〉(…に対する)欲求,切望《+『for』+『名』》 / 〈U〉(…の)『困窮』,欠乏,不足《+『of』(『for』)+『名』》 / 〈U〉『困った時』(『事態』),まさかの時 / …‘を'必要とする,要する / 《疑問文・否定文,また疑問・否定の内容を表す文で》…『する必要がある』,しなければならない / 《need not have doneの形で》…する必要はなかったのに
《方向》(1)(到着の意を含めて)…『へ』,に,まで / 《状況の変化》…[のほう]へ;…に[なるまで],その結果…になる / 《適用範囲》(1)《動詞に伴って》『…に対して』,に,へ / (2)《形容詞[句]・[代]名倍に伴って》『…に対して』 / 《程度・範囲》『…[に至る]まで』 / 《時間の終り》『…まで』(till) / 《to one's+『名』の形で》(…が)『…したことに[は]』 / 《比較・対比・割合》『…と比べて』,より,に対して / 《一致・適合》『…に合わせて』,に合って,に応じて / 《目的・意図》『…のために』 / 《運命・境遇》『…に』 / 《所属・関係》『…へ』,に[対して] / 《付加・付着・固執》『…に』 / 《対立・対向》…に[対して] / いつもの状態(位置)に / 停止(閉鎖)の状態に / 活動状態に(へ),仕事に
《名詞的用法》『…すること』 / 《形容詞的用法》『…するための,すべき』 / 《副詞的用法》『…するために』,して,するとは,すれば / 《独立用法》 / 《文全体を修飾する慣用語句》…すれば,してみると,…だが / 短縮文
麻痺(まひ)した,感覚を失った,しびれた / …‘の'感覚を失わせる,‘を'しびれさせる

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/01 06:59:00」(JST)

wiki en

The number needed to treat (NNT) is an epidemiological measure used in communicating the effectiveness of a health-care intervention, typically a treatment with medication. The NNT is the average number of patients who need to be treated to prevent one additional bad outcome (e.g. the number of patients that need to be treated for one to benefit compared with a control in a clinical trial). It is defined as the inverse of the absolute risk reduction. It was described in 1988.^[1] The ideal NNT is 1, where everyone improves with treatment and no one improves with control. The higher the NNT, the less effective is the treatment.^[2]

Variants are sometimes used for more specialized purposes. One example is number needed to vaccinate.^[3]^[4]^[5]

NNT values are time-specific. For example, if a study ran for 5 years and another ran for 1 year the NNT values would not be directly comparable. ^[6]

Derivation

NNT is the statistical inverse of the absolute risk reduction i.e. 1/absolute risk reduction. In general, NNT is computed with respect to two treatments A and B, with A typically the intervention and B the control (e.g., A might be a 5-year treatment with a drug, while B is no treatment). A defined endpoint has to be specified (e.g., the appearance of colon cancer in a five-year period). If the [probability|probabilities] p_A and p_B of this endpoint under treatments A and B, respectively, are known, then the NNT is computed as 1/(p_B – p_A). NNT is a number between 1 and ∞; effective interventions have a low NNT. A negative number would not be presented as a NNT, rather, as the intervention is harmful, it is expressed as a number needed to harm (NNH). The units of the aforementioned probabilities are expressed as number of events per subject (see worked out example below); therefore, the inverse NNH will be number of subjects per event.

Relevance

The NNT is an important measure in pharmacoeconomics. If a clinical endpoint is devastating enough (e.g. death, heart attack), drugs with a high NNT may still be indicated in particular situations. If the endpoint is minor, health insurers may decline to reimburse drugs with a high NNT. NNT is significant to consider when comparing possible side effects of a medication against its benefits. For medications with a high NNT, even a small incidence of adverse effects may outweigh the benefits. Even though NNT is an important measure in a clinical trial, it is infrequently included in medical journal articles reporting the results of clinical trials.^[7] There are several important problems with the NNT, involving bias and lack of reliable confidence intervals, as well as difficulties in excluding the possibility of no difference between two treatments or groups.^[8]

Example: statins for primary prevention

For example, the ASCOT-LLA manufacturer-sponsored study addressed the benefit of atorvastatin 10 mg (a cholesterol-lowering drug) in patients with hypertension (high blood pressure) but no previous cardiovascular disease (primary prevention). The trial ran for 3.3 years, and during this period the relative risk of a "primary event" (heart attack) was reduced by 36% (relative risk reduction, RRR). The absolute risk reduction (ARR), however, was much smaller, because the study group did not have a very high rate of cardiovascular events over the study period: 2.67% in the control group, compared to 1.65% in the treatment group.^[9] Taking atorvastatin for 3.3 years, therefore, would lead to an ARR of only 1.02% (2.67% minus 1.65%). The number needed to treat to prevent one cardiovascular event would then be 98.04 for 3.3 years.^[10]^[11]

Worked example

	Example 1: risk reduction			Example 2: risk increase
	Experimental group (E)	Control group (C)	Total	(E)	(C)	Total
Events (E)	EE = 15	CE = 100	115	EE = 75	CE = 100	175
Non-events (N)	EN = 135	CN = 150	285	EN = 75	CN = 150	225
Total subjects (S)	ES = EE + EN = 150	CS = CE + CN = 250	400	ES = 150	CS = 250	400
Event rate (ER)	EER = EE / ES = 0.1, or 10%	CER = CE / CS = 0.4, or 40%		EER = 0.5 (50%)	CER = 0.4 (40%)

Equation	Variable	Abbr.	Example 1	Example 2
EER − CER	< 0: absolute risk reduction	ARR	(−)0.3, or (−)30%	N/A
EER − CER	> 0: absolute risk increase	ARI	N/A	0.1, or 10%
(EER − CER) / CER	< 0: relative risk reduction	RRR	(−)0.75, or (−)75%	N/A
(EER − CER) / CER	> 0: relative risk increase	RRI	N/A	0.25, or 25%
1 / (EER − CER)	< 0: number needed to treat	NNT	(−)3.33	N/A
1 / (EER − CER)	> 0: number needed to harm	NNH	N/A	10
EER / CER	relative risk	RR	0.25	1.25
(EE / EN) / (CE / CN)	odds ratio	OR	0.167	1.5
EER − CER	attributable risk	AR	(−)0.30, or (−)30%	0.1, or 10%
(RR − 1) / RR	attributable risk percent	ARP	N/A	20%
1 − RR (or 1 − OR)	preventive fraction	PF	0.75, or 75%	N/A

The relative risk is 0.25 in the example above. It is always 1-relative risk reduction, or vice versa. (The signs of the numbers needed to treat and the numbers needed to hurt are reversed: NNT is 3.33 and NNH is −10.)

Simple examples

There are a number of factors that can affect the NNT. Let's say we have a disease, and a pill to treat the disease, that should work over the course of a week.

P_A is the probability of still having the disease after taking the pill (i.e. complement of the probability of being cured after taking the pill). The experimental group.
P_B is the probability of still having the disease even though you didn't take the pill (i.e. complement of the probability of the disease going away by itself). This is the control group, who probably got a placebo pill instead of the real pill.

description	P_A	P_B	NNT	interpretation
Perfect drug	0.0	1.0	1.0	Everybody is cured with the pill; nobody without
Very good drug	0.1	0.9	1.25	Ten take the pill; 8 cured by the pill, 1 cured by itself, 1 still sick.
Satisfactory drug	0.3	0.7	2.5	Ten take the pill; 4 cured by the pill, 3 cured by itself, 3 still sick.
High placebo effect	0.4	0.5	10	Ten take the pill; 6 cured but 5 of those would be cured anyway.
Low cure rate	0.8	0.9	10	Ten take the pill, one is cured by the pill, one cured by itself, 8 still have the disease.
Goes away by itself	0.1	0.2	10	Ten take the pill and 9 are cured; but 8 would have been cured anyway.
Sabotages cure	0.9	0.8	−10	Ten take the pill, two would have been cured without it, but with the pill, only one is cured, so really NNH=10.

References

^ Laupacis A, Sackett DL, Roberts RS (1988). "An assessment of clinically useful measures of the consequences of treatment". N. Engl. J. Med. 318 (26): 1728–33. doi:10.1056/NEJM198806303182605. PMID 3374545.
^ "Number Needed to Treat". Bandolier. Retrieved 2009-05-30.
^ Kelly H, Attia J, Andrews R, Heller RF (June 2004). "The number needed to vaccinate (NNV) and population extensions of the NNV: comparison of influenza and pneumococcal vaccine programmes for people aged 65 years and over". Vaccine 22 (17-18): 2192–8. doi:10.1016/j.vaccine.2003.11.052. PMID 15149776.
^ Brisson M (2008). "Estimating the number needed to vaccinate to prevent herpes zoster-related disease, health care resource use and mortality". Can J Public Health 99 (5): 383–6. PMID 19009921.
^ Lewis EN, Griffin MR, Szilagyi PG, Zhu Y, Edwards KM, Poehling KA (September 2007). "Childhood influenza: number needed to vaccinate to prevent 1 hospitalization or outpatient visit". Pediatrics 120 (3): 467–72. doi:10.1542/peds.2007-0167. PMID 17766517.
^ Palle Mark Christensen; Kristiansen, IS (2006). "Number-Needed-to-Treat (NNT) – Needs Treatment with Care". Basic & Clinical Pharmacology & Toxicology 99 (1): 12–16. doi:10.1111/j.1742-7843.2006.pto_412.x. PMID 16867164.
^ Nuovo, J.; Melnikow J.; Chang D. (2002-06-05). "Reporting number needed to treat and absolute risk reduction in randomized controlled trials.". JAMA 287 (21): 2813–4. doi:10.1001/jama.287.21.2813. PMID 12038920.
^ Hutton JL (2010). "Misleading Statistics: The Problems Surrounding Number Needed to Treat and Number Needed to Harm". Pharm Med 24 (3): 145–9. doi:10.1007/BF03256810. ISSN 1178-2595.
^ Sever PS, Dahlöf B, Poulter NR et al. (2003). "Prevention of coronary and stroke events with atorvastatin in hypertensive patients who have average or lower-than-average cholesterol concentrations, in the Anglo-Scandinavian Cardiac Outcomes Trial—Lipid Lowering Arm (ASCOT-LLA): a multicentre randomised controlled trial". Lancet 361 (9364): 1149–58. doi:10.1016/S0140-6736(03)12948-0. PMID 12686036.
^ "Bandolier — Statin effectiveness: ASCOT update". Retrieved 2008-03-31.
^ John Carey. "Do Cholesterol Drugs Do Any Good?". Business Week. Retrieved 2008-03-31.

External links

EBEM's Calculator for NNT
Online Calculator for NNT (GraphPad Software)
Centre for Evidence Based Medicine: EBM Tools: Critical Appraisal: NNT
Table of NNTs for various treatments
NNT calculator by The Garvan Institute of Medical Research

UpToDate Contents

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1. 生物統計学および疫学に関する一般用語集 glossary of common biostatistical and epidemiological terms
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Japanese Journal

日本人の食事摂取基準におけるビタミンによる疾患の発症予防の意義 : NNT(number needed to treat)の視点から

桑原晶子,田中清
ビタミン 89(1), 35-36, 2015-01-25
NAID 110009892429

救急救命士の処置拡大に関する意識度調査－血糖測定とブドウ糖溶液の投与，吸入β刺激薬，心肺機能停止前の静脈路確保－

伊関憲,大山亜紗美,林田昌子,田勢長一郎
日本救急医学会雑誌 24(9), 751-757, 2013
【はじめに】救急救命士制度は平成3年より運用され，その後静脈路確保，気管挿管，アドレナリン投与など医療行為が拡大していった。さらなる処置拡大として，血糖測定，ブドウ糖投与，重症喘息患者に対する吸入β刺激薬の吸入，心肺機能停止前の静脈路確保が図られている。今回我々は，この処置拡大に関して救急救命士が抱えている診断や技術的な問題，処置に関する自信と不安について検討を行った。【対象と方法】山形県内の現場 …
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Number Needed to Treatの確率と分布

向井淳治,石坂敏彦
医薬品情報学 15(1), 37-40, 2013
… The number needed to treat (NNT) is an index for determining the number of patients who need to be treated in order to prevent the occurrence of an adverse event when a new treatment instead of the standard one is used.Methods: The properties of NNT were examined by using the geometric distribution formula as the probability for preventing the occurrence of an adverse event in the …
NAID 130004551399

Related Pictures

★リンクテーブル★

リンク元	「治療必要数」「NNT」
関連記事	「need」「treat」「numb」「ting」「number」

「治療必要数」

　　[★]

英: number needed to treat, NNT
関: 寄与危険度、絶対危険減少

概念

何人治療すると1人イベントを減らせるかという指標
絶対危険減少(absolute risk reduction, ARR)の逆数

介入の前後である疾患の発生をx%抑える(x%減らせる)ことができたとすれば(100人治療して4人の発症を予防できた)、この逆数(100/x)が治療必要数となる(1人の発症予防のために25人の治療が必要)。

参考

1.

http://www.nakayamashoten.co.jp/ebm/pdf/key0202.pdf

国試

102B017

「NNT」

　　[★] 治療必要数, number needed to treat

「need」

　　[★]

助詞(否定・疑問文で)

(英正式)～する必要がある
[need not have done](主に英)～する必要はなかったのに(実際にはした)
(英正式)[need not do]必ずしも～でない

furthermore, aneurysms need not always be present, and angiographic findings may be limited to stenotic segments and obliteration of vessels.(HIM.2125)(さらに、動脈瘤はいつも存在するわけでないし、血管造影所見は血管の狭窄や閉塞に限られるかもしれない。)