negative predictive value

陰性的中率

WordNet

1. fix or determine the value of; assign a value to; "value the jewelry and art work in the estate"
2. the amount (of money or goods or services) that is considered to be a fair equivalent for something else; "he tried to estimate the value of the produce at normal prices" (同)economic value
3. (music) the relative duration of a musical note (同)time value, note value
4. relative darkness or lightness of a color; "I establish the colors and principal values by organizing the painting into three values--dark, medium...and light"-Joe Hing Lowe
5. the quality (positive or negative) that renders something desirable or valuable; "the Shakespearean Shylock is of dubious value in the modern world"
6. a numerical quantity measured or assigned or computed; "the value assigned was 16 milliseconds"
7. an ideal accepted by some individual or group; "he has old-fashioned values"
8. reckoned in a direction opposite to that regarded as positive; "negative interest rates"
9. a piece of photographic film showing an image with light and shade or colors reversed
10. a reply of denial; "he answered in the negative"
11. not indicating the presence of microorganisms or disease or a specific condition; "the HIV test was negative" (同)disconfirming
12. having a negative charge; "electrons are negative" (同)electronegative, negatively charged
13. characterized by or displaying negation or denial or opposition or resistance; having no positive features; "a negative outlook on life"; "a colorless negative personality"; "a negative evaluation"; "a negative reaction to an advertising campaign"
14. expressing or consisting of a negation or refusal or denial
15. having the quality of something harmful or unpleasant; "ran a negative campaign"; "delinquents retarded by their negative outlook on life"
16. less than zero; "a negative number"
17. (usually used in combination) having value of a specified kind; "triple-valued"
18. held in great esteem for admirable qualities especially of an intrinsic nature; "a valued friend"; "precious memories" (同)precious
19. of or relating to prediction; having value for making predictions (同)prognostic, prognosticative
20. beliefs of a person or social group in which they have an emotional investment (either for or against something); "he has very conservatives values"

PrepTutorEJDIC

1. 〈U〉(…の)『価値』,値打ち,有用性,重要性《+of+名》 / 〈U〉〈C〉(…の)『価格』,値段《+of+名》 / 〈U〉〈C〉《米》《修飾語句を伴って》(払った金銭に対する)正当な値打ち / 〈C〉(単語の)意味,意義 / 〈C〉値,数値 / 〈C〉音の長短 / 〈C〉色価,(色の)明暗の度 / 〈C〉《複数形で》(道義・倫理などの)価値基準,価値観 / (ある金額に)…‘を'『評価する』,見積もる《+名+at+名〈金額〉》 / …‘を'『高く評価する』,尊重する,重んじる
2. 『否定の』,反対の / 『消極的な』,控えめの / 陰電気の;(数値が)負の,マイナスの(minus);(写真が)陰画の,ネガの;(医学検査結果が)陰性の / 『否定』,拒否,「いやだ」と言うこと / 否定語[句] / 《the~》(特に討論会の)反対者側,反対派 / (電気分解に用いる)陰極板 / (数値の)負数 / (写真の)陰画,ネガ / 《しばしば受動態に用いて》…‘に'反対投票をする / =negate
3. 貴重な,高く評価される,大切な

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/01/25 22:29:09」(JST)

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[Wiki en表示]

In statistics and diagnostic testing, the negative predictive value (NPV) is a summary statistic used to describe the performance of a diagnostic testing procedure. It is defined as the proportion of subjects with a negative test result who are correctly diagnosed. A high NPV for a given test means that when the test yields a negative result, it is most likely correct in its assessment. In the familiar context of medical testing, a high NPV means that the test only rarely misclassifies a sick person as being healthy. Note that this says nothing about the tendency of the test to mistakenly classify a healthy person as being sick.

Definition

The Negative Predictive Value is defined as:

${\rm NPV} = \frac{\rm number\ of\ True\ Negatives}{{\rm number\ of\ True\ Negatives}+{\rm number\ of\ False\ Negatives}} = \frac{\rm number\ of\ True\ Negatives}{{\rm number\ of\ Negative\ calls}}$

where a "true negative" is the event that the test makes a negative prediction, and the subject has a negative result under the gold standard, and a "false negative" is the event that the test makes a negative prediction, and the subject has a positive result under the gold standard.

The following diagram illustrates how the positive predictive value, negative predictive value, sensitivity, and specificity are related.

		Condition (as determined by "Gold standard")
		Condition Positive	Condition Negative
Test Outcome	Test Outcome Positive	True Positive	False Positive (Type I error)	Positive predictive value = Σ True Positive Σ Test Outcome Positive
	Test Outcome Negative	False Negative (Type II error)	True Negative	Negative predictive value = Σ True Negative Σ Test Outcome Negative
		Sensitivity = Σ True Positive Σ Condition Positive	Specificity = Σ True Negative Σ Condition Negative

Note that the positive and negative predictive values can only be estimated using data from a cross-sectional study or other population-based study in which valid prevalence estimates may be obtained. In contrast, the sensitivity and specificity can be estimated from case-control studies.

If the prevalence, sensitivity, and specificity are known, the negative predictive value can be obtained from the following identity:

${\rm NPV} = \frac{({\rm specificity}) ({\rm 1 - prevalence})}{({\rm specificity}) ({\rm 1 - prevalence}) + (1 - {\rm sensitivity}) ({\rm prevalence})}.$

Worked example

Suppose that a fecal occult blood (FOB) screen test is used in 2030 people to detect bowel cancer:

		Patients with bowel cancer (as confirmed on endoscopy)
		Condition Positive	Condition Negative
Fecal Occult Blood Screen Test Outcome	Test Outcome Positive	True Positive (TP) = 20	False Positive (FP) = 180	Positive predictive value = TP / (TP + FP) = 20 / (20 + 180) = 10%
	Test Outcome Negative	False Negative (FN) = 10	True Negative (TN) = 1820	Negative predictive value = TN / (FN + TN) = 1820 / (10 + 1820) ≈ 99.5%
		Sensitivity = TP / (TP + FN) = 20 / (20 + 10) ≈ 67%	Specificity = TN / (FP + TN) = 1820 / (180 + 1820) = 91%

In this setting, with NPV = 99.5%, a negative test result may provide some reassurance that the subject is unlikely to have cancer. This high NPV value would be particularly notable if the cancer were relatively common. For example, if 5% of people in the population had bowel cancer, then a NPV of 99.5% would indicate that a person with a negative test result has much lower than the average population risk for bowel cancer. However if the prevalence of bowel cancer were 0.5%, a negative test result in this setting would be uninformative.

Relation to negative post-test probability

Although sometimes used synonymously, a negative predictive value generally refers to what is established by control groups, while a negative post-test probability rather refers to a probability for an individual. Still, if the individual's pre-test probability of the target condition is the same as the prevalence in the control group used to establish the negative predictive value, then the two are numerically equal.

See also

• Positive predictive value
• Sensitivity and specificity
• Diagnostic odds ratio
• Binary classification

References

• Altman DG, Bland JM (9 Jul 1994). "Diagnostic tests 2: Predictive values". BMJ 309 (6947): 102. doi:10.1136/bmj.309.6947.102. PMC 2540558. PMID 8038641. http://www.bmj.com/cgi/content/full/309/6947/102.

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Related Links

• 陰性適中率 Negative predictive value

ｽﾗｲﾄﾞ 42 / 54 一方、検査結果が陰性に出た場合のその疾患で無い確率をNegative Predictive Value （NPV)と呼ぶ。偽陰性があるために、陰性の結果でも疾患である確率は0にはならないのである。

• Diagnosis: Predictive Value

Negative Predictive Value 陰性予測力または陰性適中率: 一方で、陰性の結果が出た場合にその病気ではない確率をNegative Predictive Valueという。つまり陰性の結果が出た人の中に占める疾患に罹患していない人の割合のことである = ...

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★リンクテーブル★

リンク元	「陰性的中率」「特異度」「感度」
関連記事	「value」「negative」「valued」「predictive」

「陰性的中率」

　　[★]

英

negative predictive value

関

[[]]

• 検査結果が陰性の場合に疾患でない確率
• 感度、特異度が検査目線(検査に依存するパラメタ)であるのに対し、陽性的中率、陰性的中率は患者目線(母集団に依存するパラメタ)である。
• つまり、陰性的中率が95%のとき、臨床現場で患者さんに「検査が陰性でしたから病気の確率は95%ないと言い切れます。ですが、5%の確率で検査が間違っているかも知れません」と説明ができるかも知れない。

	疾患あり	疾患なし
検査陽性	a 真陽性	b 偽陽性
検査陰性	c 偽陰性	d 真偽性

陰性的中率 = d / ( c + d )

「特異度」

　　[★]

英

specificity

関

感度、有病率(検査前確率)、陽性適中度 陽性予測値 positive predictive value、陰性適中度 陰性予測値 negative predictive value、感度と特異度

• 無病者における検査結果が陰性である確率(流れが分かる実践検査マニュアル上巻 p.35)

	疾患あり	疾患なし
検査陽性	a 真陽性	b 偽陽性
検査陰性	c 偽陰性	d 真偽性

Sp= d / ( b + d )

感度と特異度

• 公衆衛生学的な視点から有用
• 検査をすることによって集団の中からできるだけ疾病のある人を発見したい。

「感度」

　　[★]

英

sensitivity

同

敏感度

関

特異度、有病率(検査前確率)、検査後確率、陽性適中度　陽性的中率 positive predictive value、陰性適中度 陰性的中率 negative predictive value、感度と特異度、陽性尤度比

• 有病者における検査結果が陽性である確率(流れが分かる実践検査マニュアル上巻 p.35)

	疾患あり	疾患なし
検査陽性	a 真陽性	b 偽陽性
検査陰性	c 偽陰性	d 真偽性

Sn= a / ( a + c )

「value」

　　[★]

• n.

• 値、価値

• v.

• 評価する

関

account、appraisal、appraise、appreciate、appreciation、assess、assessment、characterization、estimate、estimation、evaluate、evaluation、judgement、judgment、worth

　 　 　 　 　 　 　 　

「negative」

　　[★]

• adj.

• 陰性の、負の、ネガティブな、否定的な

関

cryptic、negatively、negativity

　 　 　 　 　 　 　 　 　 　

「valued」

　　[★]

• adj.

• 価値ある

関

meritorious、valuable、worth、worthwhile、worthy

　 　 　

「predictive」

　　[★]

• adj.

• 予測的な

関

anticipatory、predictively