Pediatric board review thread

[Socrates25]

I suppose there might be a few of us out there who are studying for boards in October. Other threads have already been started about the best way to prep so I wont rehash that again, but I figure it might be good to have a thread for any confusion with concepts or discrepancies you notice in the board review material.

I'll start off:

There's a slight discrepancy between Med Study and Laughing Your Way on statistics.

LYW says that in order to be a good screening test, it needs a high sensitivity. MS says that a good screening test needs a high PPV. Ideally I guess you need both, but if you have to choose between them, which one is superior?

I think LYW is more correct. A good screening test to me is one that picks up every possible person with the disease, even if a good number of them are false positives.

Is my thinking wrong on this or what?

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[physicsnerd42]

From what I was taught in my med school biostats class (and grad engineering imaging class) you'd want a screening test to have a high sensitivity. Remember the acronyms SpIN and SnOUT. You use a specific test to rule something in (high probability the person has the disease if positive result) and sensitive test to rule something out (high probability the person does not have the disease if negative result). A specific test has a low false positive rate and a specific test has a low false negative rate. Before you take someone to the OR you'd want a positive result in a highly specific test for their disease (let's say a positive tumor biopsy) so that you're not needless operating on people who don't have the disease.

With a screening test you're not as concerned about correctly identifying people who have the disease, so you'd want a sensitive test to rule people out. What you actually want is to be able to say to people who receive a negative result do not have the disease. People who receive a positive test result may or may not have the disease but can go for further testing with a more specific test (like a biopsy for breast cancer after a positive mammogram or biopsy for prostate cancer after high PSA) to determine who does have the disease. Again, with screening you're not necessarily identifying people with the disease you're looking for, you're trying to correctly identify people who you're confident do not have the disease so that you can avoid further testing and be confident that you haven't missed something. The false negative rate = 1 - sensitivity, so if you want a low false negative rate you want a highly sensitive test.


Are you sure MS didn't say you'd want high NPV? For a screening test, you'd want a high probability that a negative result means the person doesn't have the disease. A high NPV means that if you get a negative test result, the person is likely to be actually negative (low false negative rate), so a high NPV would be desirable for a screening test. The problem with NPV and PPV is that they're dependent on the pre-test probability of the disease whereas sensitivity and specificity are not dependent on pre-test probability.

 

[Socrates25]

Yes I double checked it, med study implies that high PPV is important for good screening test. I agree with your reasoning. Sensitivity should be the most important feature of a good screening test, high specificity is well suited for a confirmatory test.


I ran into this question on the 2011 PREP database, this question seems to have 2 right answers.

As an adjunct to sexual abstinence program at school, you are asked about the value of starting a "virginity pledge" program. Of the following, evidence suggests that the most likely outcome of such programs is:

A. formal pledges are more effective than informal
B. most pledgers abstain from oral sex
C. pledgers and non-pledgers have similar rates of STDs, assuming they are sexually active
D. pledgers are more likely than non-pledgers to abstain from vaginal intercourse
E. pledgers are more likely than non-pledgers to use condoms when sexually active



Both C and D look correct to me. PREP says C is correct. However, in their answer, they state "studies have shown that adolescents who made pledges had reduced likelihoods of engaging in intercourse or oral sex." To further complicate the matter, the ABP content specification for that question states "recognize that adolescents who participate in abstinence or abstinence pledge programs are just as likely to engage in sexual activity as those adolescents who do not participate in such programs."

 

[Socrates25]

Noticed another discrepancy on the PREP questions.

The topic is H Pylori gastritis.

PREP 2007 has a question that says you should get 2 diagnostic tests (i.e. H pylori serology, stool h pylori antigen) and if both are positive then treat w/ PPI + double antibiotic (macrolides + amox). It specifically implies that endoscopy is too invasive for a first line diagnostic test.

PREP 2012 says that H pylori tests are useless in children and are validated only in adults, therefore you should never do any kind of diagnostic testing except for endoscopy, and if positive, then obviously start PPI + double antibiotic.

I'm assuming PREP 2012 is correct and PREP 2007 is wrong -- but it begs the question as to why serologic testing for H pylori could be considered "reliable" in 2007 but bogus in 2012.

 

[tursiops495]

Noticed another discrepancy on the PREP questions.

The topic is H Pylori gastritis.

PREP 2007 has a question that says you should get 2 diagnostic tests (i.e. H pylori serology, stool h pylori antigen) and if both are positive then treat w/ PPI + double antibiotic (macrolides + amox). It specifically implies that endoscopy is too invasive for a first line diagnostic test.

PREP 2012 says that H pylori tests are useless in children and are validated only in adults, therefore you should never do any kind of diagnostic testing except for endoscopy, and if positive, then obviously start PPI + double antibiotic.

I'm assuming PREP 2012 is correct and PREP 2007 is wrong -- but it begs the question as to why serologic testing for H pylori could be considered "reliable" in 2007 but bogus in 2012.

Furthermore, First Aid 2010 says stool H. pylori Ag tests may still be indicated. After looking through UpToDate, it seems that serology has generally been abandoned due to the generally low pretest probability of H. pylori disease in this population (thus making negative studies more confirmatory). Some sources say most patients will have undetectable titers 2 years after treatment, however First Aid suggests serologic testing doesn't indicate existence of active infection.

 

[Ped23]

Hi everyone
I have a quick question. How can I get the last 5 years of board questions?

 

[Socrates25]

Hi everyone
I have a quick question. How can I get the last 5 years of board questions?

As far as I know, they dont release old board questions. The best you can do is PREP. You can buy PREP online for the last 4-5 years, it costs about $75 for each year.

 

[Ped23]

Thank you!