帮忙分析下这题啊~~

v1vian77

Appendicitis (inflammation发炎
of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ___B___.

A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis

B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis

E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that are generally associated with appendicitis

tiare

B啊

peggy在奋斗

我也很不懂这题
doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since--------这句话是什么意思呢
还有B是翻译成本来有的被诊断为没有吗？


求好心人解答

v1vian77

B啊

-- by 会员 tiare (2012/2/8 14:22:57)

求解答

蘑菇胖肉肉

这是我之前在论坛看到的解释：
“不必要”=误诊，包括“有病看成没病”以及“没病看成有病”
“必要”=正确诊断

Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before  可以理解为 新技术可以在减少不必要手术（没病诊断有病）的同时，不减少必要的手术(有病诊断没病) 。

看B选项，所有误诊的都是将没病的看成有病的。
此时，不必要的手术增加了2%，可以说是largely避免了不必要的手术。“没病看成有病”，这些没病的人做了手术，是不必要的手术，而必要的手术没有变化，还是正确诊断的98%，此时必要的手术不减少。

再看C，所有诊断有病的都确实有病。
那么2%误诊的，就有可能是“没病诊断为有病”以及“有病诊断为没病”。
如果是“没病诊断为有病”，情况同B。
如果是“有病诊断为没病”，“不必要的手术”只有2%，可以说是largely避免了不必要的手术。但是，有病的2%本应该接受手术，属于“必要的手术”，即必要的手术本应该为100%，现在却只有98%，因此“必要的手术”减少了，与目的不符。
所以C不对。

onlyonyou

明白了,谢谢!
不必要有两种,而必要只有一种!

vsflm

真心感谢四楼的~解释的真清楚！