PrepTest 158, Section 4, Question 13
Medical researcher: A new screening test detects certain(67 more words not shown)
Which one of the following(9 more words not shown)
- AA surgical operation(16 more words not shown)
- BSurgical removal of(13 more words not shown)
- CIf the new(20 more words not shown)
- DA polyp detected(13 more words not shown)
- EThe screening test(12 more words not shown)
Reading the argument
Finding a possible problem early sounds helpful. Why not use another test to find out whether the polyp is malignant before operating? The passage doesn't tell us whether that is possible, so we have to work with the situation described: uncertainty prompts doctors to remove the polyps, and the operation is dangerous.
How dangerous, compared with leaving a possible cancer untreated? Imagine, just to see the comparison, an operation carrying a 1 percent risk of death and an untreated condition carrying a 50 percent risk. Those aren't figures we're given. They show why “dangerous” alone wouldn't establish that operating is a bad decision. We would need to weigh the risks.
But the conclusion doesn't say every operation is a bad decision or that the screening test should be abandoned. It says the test can prompt dangerous operations that aren't medically necessary, because some removed polyps turn out not to be malignant.
What we’re looking for
That makes “medically necessary” the point to examine. Does finding that a polyp isn't malignant automatically settle whether it needed removal? Perhaps it needed removal for another reason, or perhaps removal was medically necessary given the uncertainty. For this assumption question, we need the author to rule out the possibility that every removal of these nonmalignant polyps was nevertheless necessary.
Working the answers
- A
Ethical justification and medical necessity aren't the same question. The author doesn't establish a rule allowing a dangerous operation only when the untreated condition is even more dangerous. Whatever we think about that rule, it isn't required to conclude that some operations weren't medically necessary.
- BCorrect
At least some removals of the nonmalignant polyps must be medically unnecessary. Otherwise, finding that some removed polyps weren't malignant would provide no basis for the conclusion.
Try the opposite: every removal of a nonmalignant polyp detected by this test was medically necessary. Then the researcher's examples wouldn't be unnecessary operations at all. That's why the reasoning needs B's modest “not always” claim. It doesn't need to say that removing a nonmalignant polyp is never necessary.
- C
This asks what we should do about a test if it encourages unnecessary operations. The argument stops before that policy decision. The test could prompt some unnecessary operations and still be worth using unchanged because of other benefits. C isn't required for the narrower conclusion about what the test can prompt.
- D
This concerns removing malignant polyps. The gap is about the polyps that turn out not to be malignant. Even accepting D would leave us asking whether removal of those other polyps was medically necessary.
- E
The usefulness of a screening test is broader than whether a particular operation is necessary. The test might provide useful information even when no treatment is required. We don't need E's restriction on usefulness to make the argument about unnecessary surgery.
More Necessary Assumption questions
Learn the LSAT our way
Our platform drills Necessary Assumption questions at your level and adjusts as you improve.