NBME 16 the unsolvables

[fatwalletuab]

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Answer and please explain if you did get them right >.<|||

3) 28. 27 y/o with hodgkins gets bone marrow transplant. two weeks after transplant, develops an erythematous, maculopapular rash, diarrhea, and elevated serum liver enzymes and bilirubin. no evidence of infection or drug reaction found. what's the mechanism of these symptoms? It’s graft vs host so answer should be c right?
a-donor macrophages secreting cytokines and affecting host cells

b-donor plasma cells ellaborating antibodies against host cells

c-donor t lymphocytes reacting against host cells

d-host macrophages secreting cytokines and affecting donor cells

e-host plasma cells ellaborating antibodies against donor cells

f-host t lymphocytes reacting against donor cells

I picked F I guess my reasoning was it take 2 weeks for the T lymphocytes to produce antibody against the graft, which is wrong.

Looks like people reasoned out to pick C, but I read from other forum people who picked C still got it wrong. Sometimes the online key is not reliable, so can someone please explain and say the correct answer, thanks
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33. A 3 yo boy has a week history of nonproductive cough, wheezing, and nausea. Coarse bilateral crackles, no other abnormality. Stool culture shows a 1.6-cm roundworm larva. CXR shows bilateral infiltrate. This disease was most likely caused by ingestion of which of
the following?
A. Feces-contaminated soil
B. Improperly canned beans
C. Pork products
D. Raw shrimp
E. Undercooked meat

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Kid with sickle cell anemia, prophylaxis with penicillin. This decreases infection for which of the following:

E coli
H. flu
N. meningiditis
Salmonella
S. pneumoniae

Penicillin should take care of s. pneumo and salmonella. Can someone tell when the buzz word "sickle cell pt" show up and I don't pick salmonella, and when I do need to pick salmonella, thanks!

 

[Jabbed]

Answer and please explain if you did get them right >.<|||

3) 28. 27 y/o with hodgkins gets bone marrow transplant. two weeks after transplant, develops an erythematous, maculopapular rash, diarrhea, and elevated serum liver enzymes and bilirubin. no evidence of infection or drug reaction found. what's the mechanism of these symptoms? It’s graft vs host so answer should be c right?
a-donor macrophages secreting cytokines and affecting host cells

b-donor plasma cells ellaborating antibodies against host cells

c-donor t lymphocytes reacting against host cells

d-host macrophages secreting cytokines and affecting donor cells

e-host plasma cells ellaborating antibodies against donor cells

f-host t lymphocytes reacting against donor cells

I picked F I guess my reasoning was it take 2 weeks for the T lymphocytes to produce antibody against the graft, which is wrong.

Looks like people reasoned out to pick C, but I read from other forum people who picked C still got it wrong. Sometimes the online key is not reliable, so can someone please explain and say the correct answer, thanks
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33. A 3 yo boy has a week history of nonproductive cough, wheezing, and nausea. Coarse bilateral crackles, no other abnormality. Stool culture shows a 1.6-cm roundworm larva. CXR shows bilateral infiltrate. This disease was most likely caused by ingestion of which of
the following?
A. Feces-contaminated soil
B. Improperly canned beans
C. Pork products
D. Raw shrimp
E. Undercooked meat

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Kid with sickle cell anemia, prophylaxis with penicillin. This decreases infection for which of the following:

E coli
H. flu
N. meningiditis
Salmonella
S. pneumoniae

Penicillin should take care of s. pneumo and salmonella. Can someone tell when the buzz word "sickle cell pt" show up and I don't pick salmonella, and when I do need to pick salmonella, thanks!

33. I would say C. This seems like a pretty cut and dry "what is the mechanism of graft vs host disease?"
34. ? I hate parasites.
35. Strep pneumo. All the bugs listed (except e. coli) have an increased incidence in sickle cell patients (auto-splenectomy), but penicillin only covers the gram positive bacteria (s. pneumoniae).

Caveat: I didn't take the NBME, just offering my opinion

 

[fatwalletuab]

anyone else have a different opinion?

 

[dropout87]

Parasite one is probably A) since it is probably ascariasis causing Loeffler syndrome.

 

[syoung]

https://en.wikipedia.org/wiki/Löffler's_syndrome

 

[fatwalletuab]

nice thanks!

 

[sluggyhobbes]

I have an issue with this parasite question, I'm also pretty sure its ascaris, but you never see larvae in the stool... you see eggs...

 

[pd1112]

It's not ascariasis, it's strongyloidiasis - also a roundworm, also causes pulmonary disease at some point in life cycle, and more correctly fits the feces-contaminated soil aspect because it can burrow into the skin, unlike Ascaris, which must be ingested.

 

[GUH]

35. Strep pneumo. All the bugs listed (except e. coli) have an increased incidence in sickle cell patients (auto-splenectomy), but penicillin only covers the gram positive bacteria (s. pneumoniae).

I agree with your answer (since the Sickle Cell diagnosis is pushing us towards Salmonella or Strep Pneumo and Penicillin isn't used for Gram negative rods), but can't Penicillin also be used for Gram negative cocci like Neisseria?

 

[pd1112]

I agree with your answer (since the Sickle Cell diagnosis is pushing us towards Salmonella or Strep Pneumo and Penicillin isn't used for Gram negative rods), but can't Penicillin also be used for Gram negative cocci like Neisseria?

Only if the strain doesn't produce penicillinase. When prophylactically treating, you wouldn't choose a drug with possible resistance.

 

[ApolloStrut]

I know this thread is a year old but for those looking through these NBME 16 threads here's my two cents on the second question:

The stem asks which was most likely INGESTED so it can't be Strongyloides. It's probably not Ascaris either because like someone else said you find eggs in the stool, not larva. I'm thinking the patient has Pediatric Toxocariasis (Toxocara canis - Visceral larva migrans affecting the lungs). It matches signs and symptoms, 1-7 yo are most commonly affected, larva is found in the stool and the primary means of infection is ingestion (toddlers eating dirt on the playground). The feces is likely dog feces (hence Toxocara CANIS). http://emedicine.medscape.com/article/999850-clinical

 

[PowerDan]

How hard was NBME 16?

 

[canary90]

It requires more thinking and has more convuluted stems compared to earlier NBMEs

 

[PowerDan]

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[canary90]

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[PowerDan]

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[canary90]

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[PowerDan]

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[canary90]

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[Kazaki]

4) Female patient (~ 65 years old) with family history (brother and mother) of colon cancer refuses to consent to colonoscopy but ready to have her stool tested for blood. Why is stool test for occult blood not appropriate for her?

I say low sensitivity, even though occult stool blood has low sensitivity and specificity for colon cancer. A good screening test should be highly sensitive (or have a high negative predictive value) i.e. when the test is negative, you most likely don't have the disease. With high specificity, you get a high positive predictive value i.e. if it's positive, you've got the disease. This is why we use tests with high specificity for confirmation, not screening.

3) Effects of smoking on pulmonary defenses

Mucous production increases
Cilia activity decreases
Macrophage function decreases.

Kid with sickle cell anemia, prophylaxis with penicillin. This decreases infection for which of the following:

E coli
H. flu
N. meningiditis
Salmonella
S. pneumoniae

Penicillin should take care of s. pneumo and salmonella. Can someone tell when the buzz word "sickle cell pt" show up and I don't pick salmonella, and when I do need to pick salmonella, thanks!

GI E.coli infections are not treated with antibiotics
H flu can be treated with amoxicillin+clavulinic acid. So I guess susceptible to penicillinS as a class of antibiotics, but not to penicillin G
Meningococcus can be treated with penicillin G
Salmonella is treated with fluroquinolones
S. pneumoniae is treated with ceftriaxone or a macrolide

So I think the answer is meningococcus.

 

[canary90]

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[Kazaki]

Hey there, thanks for the explanation!
As you mentioned a screening test should usually have a high sensitivity to rule out a disease. But isn't Fecal occult blood test routinely used as a screening test? We don't go around doing colonoscopy for everyone. So if FOB has low sensitivity, why is it used as a screening test in the first place?

There is no better alternative as of now. You said it, we can't go around shoving stuff up people's bum holes "just to be safe". Colonoscopies are invasive, and they aren't cheap. MRIs aren't necessarily cheap either. CT scans are cheaper, and with 3D colonoscopies available through CT, I think we're going to see a rise in the use of the technology for detecting malignancies. But until it can be cost effective to be used as the go to test, we won't see it being used a screening test.
Maybe that's why colon cancer has a high mortality rate?

 

[canary90]

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[Kazaki]

Agreed, makes sense!
I assumed while solving NBME that since FOB is used as a screening test, it should have a high sensitivity but since its not a confirmatory test, the specificity should be low... I am still kind of confused though; why "low specificity" would be a wrong choice since its anyway less specific too? 🤔

Great point. But you have to go back to the question and read the case. She has a history of colon cancer, but no symptoms (as far as the question is concerned). Why does the physician want to test her? +++history and age are risk factors. Testing someone for a disease they might not have with no symptoms is screening. Screening means focus on sensitivity because we want to RULE OUT disease i.e. we want a high NEGATIVE PREDICTIVE VALUE. It's low specificity still makes it a not-so-good test, but that isn't what the question is asking for.
If it had been about the same woman and the question said "FOB was positive, the physician tells the patient that this doesn't mean you have cancer. Why did the physician say that?" In this situation, although the sensitivity is still low, the answer would be low specificity because the question is really asking you "a test with low ______ cannot be used as a confirmatory test"

Hope that cleared it up.
Edits are in bold.

 

[canary90]

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[Kazaki]

👍

 

[PowerDan]

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[PowerDan]

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[PowerDan]

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[Kazaki]

Did you get this one right on the form?

Didn't do 16 yet, but the answer makes sense so far. I'll let you know when I take it.

Why would Macrophage function decrease though?
Clearing dust from the respiratory tract being the job of the macrophages, shouldn't their activity increase under conditions of increased smoke/dust?

Also, why would ciliary activity decrease? Is it because smoke directly damages the cilia, thus decreasing their activity?

I assumed macrophage function would increase, but according to papers published on this, enzyme function of macrophages decreases in smokers. I think it's the chemicals in smoke that interfere with macrophage function. Maybe that's part of the reason why smokers develop more infections?
Smoking stuns cilia. I remember an attending pulmonologist told me that 1 cigarette can stun your cilia for a few days.

I am pretty sure the answer is Strep pneumo. I picked that and it hasn't appeared on my list of incorrects.

Really? But everywhere I read, it says that strep pneumo is treated with ceftriaxone. If memory serves, penicillin is now only used for syphilis and endocarditis so what's the point of the question to begin with haha

 

[canary90]

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[Kazaki]

Hey Kazaki,
Really appreciate your help and explanations. They are of great help to us. I was about to post another question but got a little concerned. The advice that I have gathered from people is that one must take NBMEs to predict one's score (and of course learn from the mistakes). If you have already seen the NBME questions and their explanations, when you take the real NBME assessment, you'd already know their answers and the predicted score would probably be biased/not accurate.
Please don't get me wrong. Just want to caution you 🙂🤔

Very true. I just couldn't resist haha.
Given that, I'll probably still choose whatever I think is correct.
Appreciate the advise though

 

[PowerDan]

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[canary90]

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[canary90]

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[PowerDan]

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[canary90]

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