Question 9 clarification

Question 9 clarification

by Pingyang Liu -

I am confused by Q9-C. 

The question stem ask which COULD lead to the slight increase and the answer choices are  Yes, No, Cannot tell. If A could lead to increase under some situations, but no increase under other situations, are we supposed to choose Yes or Cannot tell?

Also, are we assuming that there is only one golden standard of liver cancer diagnosis in this article or there are multiple golden standards depending on the tests results, or the tests(AFP and ultrasound are also used to diagnose liver cancer in this article)? 

In the textbook, 

Differential verification bias is a common problem with cancer screening tests. We will see in Chapter 10 (on screening tests) that many cancers are clinically harmless; they can either resolve spontaneously or just sit there and never cause the patient any problem.  Consider a person with such a cancer, or for that matter any currently detectable disease destined to resolve on its own.  If he tests positive, he will get the invasive test, we'll find the disease and give the test credit for getting the right answer, a true positive.  If he tests negative, he'll get clinical follow-up and remain well, and once again we will give the test credit for getting the right answer, a true negative. 

Do we take consideration in this question that some diagnosed cancer would resolve spontaneously?


Thanks.

Best,

Pingyang

Re: Question 9 clarification

by Thomas Newman -

Hi,m Pingyang --

Unless we are looking at different versions of the exam, I think you are referring to problem 8c.  In any case, it's the problem about screening for liver cancer.

1. The question stem ask which COULD lead to the slight increase and the answer choices are  Yes, No, Cannot tell. If A could lead to increase under some situations, but no increase under other situations, are we supposed to choose Yes or Cannot tell?

I would say if the bias COULD lead to an increase under some situations you should indicate Yes.

2.  Also, are we assuming that there is only one golden standard of liver cancer diagnosis in this article or there are multiple golden standards depending on the tests results, or the tests(AFP and ultrasound are also used to diagnose liver cancer in this article)? 

AFP and ultrasound were the screening tests; you can assume that those who tested positive received some additional evaluation (probably biopsies) to make the diagnosis of liver cancer.  

3. Do we take consideration in this question that some diagnosed cancer would resolve spontaneously?  

Yes, I think that it would be reasonable to consider this possibility.  But see also an earlier post from Michael about biases discussed in Chapter 4 vs Chapter 10.  In chapter 4 we were talking about studies of diagnostic test accuracy; in Chapter 10 the biases affect our judgement of the outcome of the tests.

Re: Question 9 clarification

by Pingyang Liu -

Thanks for your explanation. It is very helpful.


Best,

Pingyang