USMLE NBME 18 - Questions and Answers - Discussions & Explanations

[TheAberrantGene]

NBME 18 has been released and is available on regular and extended feedback.
I will be taking it fairly soon as my exam is around the corner.
Let's continue the great trend on this forum and start a discussion once people start taking it,

Best of luck fellas !

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[chupunkua]

Lol! How did your latest nbmes go? What's your target?

i did some real stupid planning and did 3 nbmes offline. had about 25-30 wrong questions each then i took 15 couple of weeks ago online and scored 250. this one i only scored 228. its a big difference and my exam is in exactly 1 week. i am a 5 year old img so the target is 250. my basics are not as fresh as most

 

[cachexia]

I had the first 2 wrong
For the first one, you had to multiply protein grams with 4 and subtract it from 2000(calories allowed/day). They gave a fat/carb ratio of 30:55. So for the fat calories, you had to multiply the left over calories with 33/(30+55) or 33/85.

2q- 6/1000

3q- Sub cutaneous tissue

hey y s it 6/1000 can u explain plzz..

 

[AnxietyAnnie]

I am aiming for a 250 too and I pushed my date to early April after getting a 247 in this one. Otherwise my planned date was 3 days from today.

 

[cachexia]

i did some real stupid planning and did 3 nbmes offline. had about 25-30 wrong questions each then i took 15 couple of weeks ago online and scored 250. this one i only scored 228. its a big difference and my exam is in exactly 1 week. i am a 5 year old img so the target is 250. my basics are not as fresh as most

same here.. m feeling soo lost n disappointed.. donno whether to give d exam r postpone it..

 

[AnxietyAnnie]

hey y s it 6/1000 can u explain plzz..

30% of the patients would get admitted after the procedure so a 1/3 chance roughly. Then 2% of those patients get infected so a 2/100 chance or a 1/50 chance.
Multiplying both probabilities
1/3 into 1/50 equals 1/150. Now if we convert this into %, it becomes .66% or roughly 6/1000

 

[cachexia]

I am aiming for a 250 too and I pushed my date to early April after getting a 247 in this one. Otherwise my planned date was 3 days from today.

yea ds nbme s sooo depressing.. m thinking f postponing my exam too.. but my triad ends ds month.. such a stupid nbme

 

[cachexia]

30% of the patients would get admitted after the procedure so a 1/3 chance roughly. Then 2% of those patients get infected so a 2/100 chance or a 1/50 chance.
Multiplying both probabilities
1/3 into 1/50 equals 1/150. Now if we convert this into %, it becomes .66% or roughly 6/1000

oh thanq so much..

 

[chupunkua]

I am aiming for a 250 too and I pushed my date to early April after getting a 247 in this one. Otherwise my planned date was 3 days from today.

i am taking 17 tomorrow and will decide if want to delay it for a couple of weeks

 

[cachexia]

yea ds nbme s sooo depressing.. m thinking f postponing my exam too.. but my triad ends ds month.. such a stupid nbme

how much did u pay fr postponing d exam?

 

[chupunkua]

what is the answer for HOX gene question . a new born has a cervical rib
A . expression of a HOX gene normally expressed only caudal to c7
B expression of a HOX gene normally expressed only cranial to c7
C lack of expression of a HOX gene normally expressed at c7
D over expression of hox gene normally expressed at c7\
E Under expression of a Hox gene normally expressed at C7

i know it is blueprint for morphogenesis and axial skeleton development. please explain

 

[cachexia]

yea ds nbme s sooo depressing.. m thinking f postponing my exam too.. but my triad ends ds month.. such a stupid nbme

i am taking 17 tomorrow and will decide if want to delay it for a couple of weeks

how much did u pay for postponing d exam?

 

[cachexia]

what is the answer for HOX gene question . a new born has a cervical rib
A . expression of a HOX gene normally expressed only caudal to c7
B expression of a HOX gene normally expressed only cranial to c7
C lack of expression of a HOX gene normally expressed at c7
D over expression of hox gene normally expressed at c7\
E Under expression of a Hox gene normally expressed at C7

i know it is blueprint for morphogenesis and axial skeleton development. please explain

donno but i marked A and got it ryt..

 

[AnxietyAnnie]

@chupunkua GL with 17, it is relatively easier. There is just a lot more pressure on us IMGS to score well. We shouldn't take any risks.
@cachexia Naaathing. I had planned to book my date after 18, and I had a 2 point drop after 2 weeks of study so I booked a date in early April.

 

[DarkKnight3]

What is C-Jun transcription factor? I completely guessed on this column and somehow got the question right, but I still don't know the significance of it even after spending almost an hour googling...

 

[AnxietyAnnie]

What is C-Jun transcription factor? I completely guessed on this column and somehow got the question right, but I still don't know the significance of it even after spending almost an hour googling...

These are produced in the end of MAPK pathway. They(FOS and JUN) are early response elements which help in transcription of late response elements. What I don't understand is their relationship with endothelin. That q was pure guess work for me.

 

[DarkKnight3]

These are produced in the end of MAPK pathway. They(FOS and JUN) are early response elements which help in transcription of late response elements. What I don't understand is their relationship with endothelin. That q was pure guess work for me.

according to Wikipedia they play a role in apoptosis. "Overexpression of c-jun in cells results in decreased level of p53 and p21, and exhibits accelerated cell proliferation." ahhhh it all makes sense now!!

 

[breadlover72]

what is the answer for HOX gene question . a new born has a cervical rib
A . expression of a HOX gene normally expressed only caudal to c7
B expression of a HOX gene normally expressed only cranial to c7
C lack of expression of a HOX gene normally expressed at c7
D over expression of hox gene normally expressed at c7\
E Under expression of a Hox gene normally expressed at C7

i know it is blueprint for morphogenesis and axial skeleton development. please explain

I got it wrong but I do know HOX works in a craniocaudal direction... anybody else? I couldn't wrap my head around this one.

 

[AnxietyAnnie]

according to Wikipedia they play a role in apoptosis. "Overexpression of c-jun in cells results in decreased level of p53 and p21, and exhibits accelerated cell proliferation." ahhhh it all makes sense now!!

Do you remember what was endothelin's role in that question? I can't remember but I do remember that it was a tricky q for me.

 

[DarkKnight3]

Do you remember what was endothelin's role in that question? I can't remember but I do remember that it was a tricky q for me.

The question had to do with ventricular hypertrophy if I'm not mistaken. So B-myosin heavy chain would increase. This leads to a diastolic dysfunction in which the ventricle can't accommodate all the blood and so there's backup. Eventually this is gonna lead to pulmonary HTN which is where endothelium comes into play. (I base this on the fact that the drug Bosentan is used in pulm HTN and antagonizes endothelin). So endothelin will increase. In order for this process to progress, C-JUN needs to increase because it is anti-apoptotic... This was my logic in doing this question (except when I did it I had to guess on C-JUN).

 

[AnxietyAnnie]

I got it wrong but I do know HOX works in a craniocaudal direction... anybody else? I couldn't wrap my head around this one.

Hox genes (also known as homeotic genes) are a group of related genes that control the body plan of an embryo along the cranio-caudal (head-tail) axis. After the embryonic segments have formed, the Hox proteins determine the type of segment structures (e.g. legs, antennae, and wings in fruit flies or the different types of vertebrae in humans) that will form on a given segment. Hox proteins thus confer segmental identity, but do not form the actual segments themselves.[1] From Wikipedia

So if they decide, what appendage goes at what vertebral level, their expression at the wrong v-level can result into a rib at C-7

 

[DarkKnight3]

I got it wrong but I do know HOX works in a craniocaudal direction... anybody else? I couldn't wrap my head around this one.

I can give u my interpretation of how I got the question right. The rest is up to you. So we know HOX genes are involved in development. There is an extra cervical rib that shouldn't be there. It is above the normal ribs. So based on this, the HOX gene is over expressing a gene that should begin to be expressed one level below or caudally. Thus the answer.

The gene is normally expressed below C7 and NOT AT C7. Hope this helps.

 

[AnxietyAnnie]

The question had to do with ventricular hypertrophy if I'm not mistaken. So B-myosin heavy chain would increase. This leads to a diastolic dysfunction in which the ventricle can't accommodate all the blood and so there's backup. Eventually this is gonna lead to pulmonary HTN which is where endothelium comes into play. (I base this on the fact that the drug Bosentan is used in pulm HTN and antagonizes endothelin). So endothelin will increase. In order for this process to progress, C-JUN needs to increase because it is anti-apoptotic... This was my logic in doing this question (except when I did it I had to guess on C-JUN).

Thanks I actually had issue with how those 3 variables were ordered. lol
For me, the order should have been, increased C-Jun, Increased Beta Myosin, Increased Endothelin.

 

[chupunkua]

how much did u pay fr postponing d exam?

i looked at it today . if you just postpone the exam 5 days before the test then it is $50 but if you want to extend the 3 month period

I can give u my interpretation of how I got the question right. The rest is up to you. So we know HOX genes are involved in development. There is an extra cervical rib that shouldn't be there. It is above the normal ribs. So based on this, the HOX gene is over expressing a gene that should begin to be expressed one level below or caudally. Thus the answer.

The gene is normally expressed below C7 and NOT AT C7. Hope this helps.

i like your explanation.

 

[breadlover72]

i looked at it today . if you just postpone the exam 5 days before the test then it is $50 but if you want to extend the 3 month period

5 days or more before $50; less than 5 days before $114... just thought I'd add that in there.

 

[dempty]

this is how i thought of it, simply put:
a- the meta-analysis concluded that the if a person has a mutation in one of those 32 loci (aka positions within the genome), then that person's risk of acquiring crohn's increases by 10%
b- a heritability rate of 50% basically means that if one twin has crohn's, then his other twin has a 50% chance of developing crohns as well, which means the genetic aspect of crohn's is much stronger than the 10% that the meta-analysis suggested

from "a" and "b", we can assume that the study only discovered 10% of the genes whereas the genetic factor is actually closer to 50%, therefore, "the identified loci account for a small part of the variance" = the genes that this study was able to identify are only a small fraction of the complete genes that cause crohn's aka those researchers need to stop procrastinating and do a better job.
it's more of a word game than an actual medical question
@DarkKnight3 @AnxietyAnnie @breadlover72

An investigator conducts a meta-analysis of three genome-wide association studies of Chron Disease. The studies encompassed 3200 cases and 4800 controls, all of European descent. The initial studies identified 11 significant loci with odds ratios above 1.3 and 1.5; the combined meta-analysis identified an additional 21 loci with odd ratio of 1.1 to 1.3. It is estimated that the 32 loci identified explain about 10% of the variance in disease risk with 2 loci accounting for 2% of the variance. Previous studies of twins indicated a 50% heretability rate for Chron's disease. Which of the following best explains these results?
A. analysis of 1000 cases or less are as informative as meta-analysis
B. The identified loci account for a relatively small part of the variance
C. The majority of contributing loci have been identified
D. Majority of loci have major effects on disease appearance
E. Two loci provide evidence for autosomal dominant inheritance of Chron D

One thing to consider about the question option B is that they're likely looking at it from some type of independent variables (loci) explaining the dependent variable (disease risk [odds])(logistic regression framework). At best, we can explain 100% of the variation in the dependent variable with our independent variables (although, something is usually off if this happens). So, they're telling you that all the loci only account for 10% of the variation observed in disease risk, which means that 90% is unexplained by the loci they have. B seems reasonable from this perspective, so how can we nix the other choices?

A- doesn't really make sense, as the theory behind a meta-analysis tells us that a bunch of well done studies can be synthesized to provide more insight than a smaller study.
C- doesn't have to follow, and doesn't exactly jive with the twin studies that indicate a large genetic component.
D- can't be said for sure from that information
E- as another poster pointed out, E isn't supported by 2 loci only accounting for 2% of the variation in risk of disease.

B is the only sound answer choice, for a pretty simple reason (all these identified loci only explain 10% of the variation in disease risk).

 

[ciphressinchief]

35-year old man w several episodes of squeezing chest pain gets angiogram... gets IV NE. Question shows a graph of coronary blood flow with a drop after the NE and then a rise. Question asks which substance causes the increased total coronary blood flow 1-2 mins after NE

a) adenosine
b) AT II
c) epinephrine (wrong... was thinking something about NE releasing Epi, which then triggers beta2 receptors)
d) histamine (only vasodilator on the list... but why would this be released?)
e) thromboxane A2 (think this might be right... Prinzmetal angina is mediated by TxA2 but not sure why this would cause increased blood flow)

Any thoughts?

 

[breadlover72]

35-year old man w several episodes of squeezing chest pain gets angiogram... gets IV NE. Question shows a graph of coronary blood flow with a drop after the NE and then a rise. Question asks which substance causes the increased total coronary blood flow 1-2 mins after NE

a) adenosine
b) AT II
c) epinephrine (wrong... was thinking something about NE releasing Epi, which then triggers beta2 receptors)
d) histamine (only vasodilator on the list... but why would this be released?)
e) thromboxane A2 (think this might be right... Prinzmetal angina is mediated by TxA2 but not sure why this would cause increased blood flow)

Any thoughts?

I believe I put adenosine which causes coronary vasodilation.

 

[ciphressinchief]

I believe I put adenosine which causes coronary vasodilation.

Thanks! Completely spaced that adenosine does that.

 

[breadlover72]

Thanks! Completely spaced that adenosine does that.

How about the women with PCOS who needs to make diet and exercise changes - what would help her adherence?

a) Give her publications appropriate for her education level
b) ask her to bring a family member or friend to next visit
c) inform her of consequences of not treating
d) make follow up appts to tract progress
e) refer to support group (wrong)

No problem, I missed a couple that my brain just completely forgot somehow, it happens.

We actually mentioned this one somewhere on here...but follow up appointments and monitor progress.

 

[ciphressinchief]

No problem, I missed a couple that my brain just completely forgot somehow, it happens.

We actually mentioned this one somewhere on here...but follow up appointments and monitor progress.

Ha, yeah, figured that out and edited the original post

 

[ciphressinchief]

25. A 16-year-old girl calls the physician on a Friday night 2 hours after a condom broke during sexual intercourse with her boyfriend. She asks the physician to prescribe an emergency oral contraceptive. The physician on call is not the patient's regular physician and does not dispense emergency contraception for moral reasons. After the physician respectfully informs the patient that he does not prescribe this contraceptive, it is most appropriate for the physician to state which of the following?
A
) "I am obligated to discuss this with your parents."
B
) "I can have one of my colleagues call you back to further discuss your concerns."
C
) "I recommend that you call the local women's health clinic."
D
) "I will tell your regular physician to call you on Monday to talk with you about your situation."
E
) "I'm sorry, but you will have to research other ways to obtain the prescription yourself."
Can someone explain why C is wrong... Aren't you supposed to refer them elsewhere?

If you are a conscientious objector (for abortion, birth control, etc), you are required to refer to a colleague who will perform the procedure. Asking this pt to call the local women's clinic is putting the onus on her to figure it out instead of linking her with a different provider.

 

[WeedForLunch]

what is the answer for HOX gene question . a new born has a cervical rib
A . expression of a HOX gene normally expressed only caudal to c7
B expression of a HOX gene normally expressed only cranial to c7
C lack of expression of a HOX gene normally expressed at c7
D over expression of hox gene normally expressed at c7\
E Under expression of a Hox gene normally expressed at C7

i know it is blueprint for morphogenesis and axial skeleton development. please explain

I used this..
It helped me a lot...
While the exact C7 thing is not in there.. it answered my questions about this..

Also, there is a question in UW about this topic...
And in DIT they talk about HOX D 13 gene which causes synpolydactyly...

 

[myeloma71]

Thank you very much for your replies guys.

4 yr male with recurrent UTIs, left kidney found small and non functional, nephrectomy done, picture shown
a- diffuse cortical necr
b- fibromuscular dysplasia
c- neoplastic
d- thing GBM (wrong)
e- tubular atrophy

was this PUJO with hydronephrosis and eventual atrophy? if yes, what's the pthological change?

i got this right. but i dont remember the reasoning. can anybody explain ?

 

[breadlover72]

i got this right. but i dont remember the reasoning. can anybody explain ?

I got it wrong but I'm pretty sure they were trying to go for hydronephrosis and chronic pyelonephritis (recurrent UTIs) where you'd have tubular atrophy. Can someone confirm?

 

[cachexia]

i got this right. but i dont remember the reasoning. can anybody explain ?

u remember wat u marked?? i thought ans B shud b ryt.. coz f increased pressure in arteries vascular proliferation s present ..

 

[USMLERock]

1)65 YO, 1 week Hx swollen, painfull knee, temp 38, BP 110/65. Exm left knee erythema and swelling and decr ROM. Pt synovial contain
a. hydroxyapatite
b. lymphocyte
c. n. gonorrhea
d. Trepnm Pallidum
e. uric acid

2)Newborn recurrent vomitting after feeding, had no fever abd examination shows firm, mobile massin epigastrium to right midline, pt condition ?
a. amniotic band disruption sequence
b. breech disruption sequence
c. multiple malform syndrome
d. single primary developmental def
e. vater

 

[myeloma71]

uric acid
single primary developmental defect i think. correct me if im wrong.

 

[myeloma71]

u remember wat u marked?? i thought ans B shud b ryt.. coz f increased pressure in arteries vascular proliferation s present ..

yes im pretty sure i marked tubular atrophy.
fibromuscular dysplasia is mc seen in younger women

 

[jqueb29]

uric acid
single primary developmental defect i think. correct me if im wrong.

Curious if #2 might instead be VATER, assuming that I'm correct in saying that patient has duodenal atresia. Source: http://emedicine.medscape.com/article/940615-overview

 

[chupunkua]

a 4 day old boy is brought to the pediatricians office early in the morning because he had vomited throughout the night after breastfeeding. Physical examination is normal except for lethargy and dry mucus membranes. Lab studies show
serum
Na 139
Cl 90
K 7.0
HCO3 17
Glucose 42
BUN 25
creatinine .4
17 OH progesterone
the most likely explanation for these findings is a deficiency in which of the following enzymes
A 20,22-desmolase
B 11B hysroxylase
C 17 a Hysroxylase
D 21 Hydroxylase
E 17 ketoreductase

is the answer D in this question?

 

[USMLERock]

3) 45 YO joint paint due to rheumatoid arthritis. OTC has been ineffective. Physician plans initiate DMARD, Physician also prescribed another agent to be used until DMARD effective.
a. auronofin
b. etanercept
c. hydroxychloroquine
d. infliximab
e. prednisolone

4) a 35 YO brought to physician because worsening behavior, he tells physician CIA spying on him, hearing a voice CIA plans to kill him. unkempt hair and poor hygine. mental status pt is most likely show which ?
a. flattened affect
b. Inability to state his name
c. inability to write his name
d. lack of orientation of place/ time
e. long term memory impairment

 

[chupunkua]

A 48 year old woman with SLE. current medication include daily prednisone , hydroxychloroquine and oxycodone for pain. which of the following is th emost appropriate action by the physician to encourage healthy adaptation to illness in this patient
A encourage to partcipate in support group
B explain all abnormal findings in detail
C Fill necessary paperwork for disability
D List all serious medical conditions she will develop if she does not follow her medication
E provide patient with written info on pathophys of SLE

 

[myeloma71]

3) 45 YO joint paint due to rheumatoid arthritis. OTC has been ineffective. Physician plans initiate DMARD, Physician also prescribed another agent to be used until DMARD effective.
a. auronofin
b. etanercept
c. hydroxychloroquine
d. infliximab
e. prednisolone

4) a 35 YO brought to physician because worsening behavior, he tells physician CIA spying on him, hearing a voice CIA plans to kill him. unkempt hair and poor hygine. mental status pt is most likely show which ?
a. flattened affect
b. Inability to state his name
c. inability to write his name
d. lack of orientation of place/ time
e. long term memory impairment

prednisone because dmards take time to work. in the mean time steroids/nsaids are used

flattened effect ( schizophrenia)

 

[myeloma71]

A 48 year old woman with SLE. current medication include daily prednisone , hydroxychloroquine and oxycodone for pain. which of the following is th emost appropriate action by the physician to encourage healthy adaptation to illness in this patient
A encourage to partcipate in support group
B explain all abnormal findings in detail
C Fill necessary paperwork for disability
D List all serious medical conditions she will develop if she does not follow her medication
E provide patient with written info on pathophys of SLE

support group

 

[myeloma71]

30y/o women long standing PID surgical resection of scarred segment of fallopian tube. which inflammatory cell ?

basophils
eosinophils
macrophages
mast cells
neutrophils

is it macrophages due to chronic inflammation ??

 

[myeloma71]

a 4 day old boy is brought to the pediatricians office early in the morning because he had vomited throughout the night after breastfeeding. Physical examination is normal except for lethargy and dry mucus membranes. Lab studies show
serum
Na 139
Cl 90
K 7.0
HCO3 17
Glucose 42
BUN 25
creatinine .4
17 OH progesterone
the most likely explanation for these findings is a deficiency in which of the following enzymes
A 20,22-desmolase
B 11B hysroxylase
C 17 a Hysroxylase
D 21 Hydroxylase
E 17 ketoreductase

is the answer D in this question?

yes D

 

[myeloma71]

Curious if #2 might instead be VATER, assuming that I'm correct in saying that patient has duodenal atresia. Source: http://emedicine.medscape.com/article/940615-overview

does vater involve duodenal atresia ?? i was thinking more like tracheoesophageal fistuala

 

[chupunkua]

30y/o women long standing PID surgical resection of scarred segment of fallopian tube. which inflammatory cell ?

basophils
eosinophils
macrophages
mast cells
neutrophils

is it macrophages due to chronic inflammation ??

i think so. that was my thinking when i chose the answer

 

[breadlover72]

Curious if #2 might instead be VATER, assuming that I'm correct in saying that patient has duodenal atresia. Source: http://emedicine.medscape.com/article/940615-overview

Palpable olive like mass = pyloric stenosis. Single primary developmental defect (I got it right)
@myeloma71 @USMLERock

 

[wombthereitis]

19 y/o man, GI bleeding, 5 cm blind out pouching of terminal ileum..... is this Meckel's Diverticulum? I don't think I took it into consideration given the patient's age? Was the answer heterotrophic gastric mucosa? Thanks in advance!