USMLE NBME 18 - Questions and Answers - Discussions & Explanations

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TheAberrantGene

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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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Getting in this thread early. Like this ****

Read the s-hit outta these NBMEs guys.. you will have many many questions directly or based on stuff you will see in the NBMEs and nowhere else in step prep material...
Source: I gave my test a while ago and got a good score.. and the above is based on my experience..
 
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Anyone took this ? taking this ?

I am in 3 hours... reply to this post in case you wanna go over wrong questions.
Thanks !
 
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just gave it
Wasn't too bad... I was kinda up since 3 days with just 2 hrs of sleep each night so made 6-8 or so dumb f*ck mistakes.

I will be posting questions here... please do contribute.. inputs will be much much appreciated... thanks..
 
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Taking 16 in 5 days or so.. hope to go over 270... if other people have taken this please do come on this thread..
 
Anyone up for helping me with a couple of Qs?

1. Man has Cushing's syndrome. Low ACTH, high cortisol. What will happen to ACTH and cortisol after low-dose dexamethasone suppression test? Arrows for ACTH either going up or no change, and cortisol up, down or no change.

2. Girl has chronic cough with thick sputum, abdominal cramps in RLQ, and frequent resp infections. Clubbing of fingers, hyperresonance on chest percussion. Diffuse crackles and scattered wheezes. On xray - diffuse hyperinflation of the right upper lobe. She has a healthy brother. What's the likelihood he is a carrier for the condition.

3. Woman with lupus and nephritic syndrome. What would be on the renal biopsy?
a) crescent shaped glomeruli
b) inflamatory infiltrates in the interstitium
c) mesangial cell proliferation
d) sclerosed glomeruli
e) subepithelial deposits


Thanks))
 
Please could u post like the block and the q number or atleast the original stem ?
I cant find the questions exactly.. many of em were baiting you for another diagnosis.. so maybe the simplified version you have written like "Woman with lupus and nephritic syndrome. What would be on the renal biopsy? " may not have been all there was in the question..
 
Anyone up for helping me with a couple of Qs?

2. Girl has chronic cough with thick sputum, abdominal cramps in RLQ, and frequent resp infections. Clubbing of fingers, hyperresonance on chest percussion. Diffuse crackles and scattered wheezes. On xray - diffuse hyperinflation of the right upper lobe. She has a healthy brother. What's the likelihood he is a carrier for the condition.

Got this right... 2/3 i think it was the last option maybe..

basically its AR and the male kid is born phenotypically normal... the point being that 2/3 of all phenotypically normal kids would be carriers..

Say Aa Aa are parent both carriers A dominant normal, a recessive abnormal
Now the girl got aa and was diseased..

the boy is normal...so cant be aa... so u eliminate that possibility.. the 3 possibilities left are : Aa Aa and aa in the Mendelian diagram.. 2 out of 3 carrierr..



I dont know which questions you are referring to when you write the 1st and 3rd one.. they are oversimplified... the question may not have been what you think... write out the full stem
 
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Anyone up for helping me with a couple of Qs?

1. Man has Cushing's syndrome. Low ACTH, high cortisol. What will happen to ACTH and cortisol after low-dose dexamethasone suppression test? Arrows for ACTH either going up or no change, and cortisol up, down or no change.

2. Girl has chronic cough with thick sputum, abdominal cramps in RLQ, and frequent resp infections. Clubbing of fingers, hyperresonance on chest percussion. Diffuse crackles and scattered wheezes. On xray - diffuse hyperinflation of the right upper lobe. She has a healthy brother. What's the likelihood he is a carrier for the condition.

3. Woman with lupus and nephritic syndrome. What would be on the renal biopsy?
a) crescent shaped glomeruli
b) inflamatory infiltrates in the interstitium
c) mesangial cell proliferation
d) sclerosed glomeruli
e) subepithelial deposits


Thanks))
is the 3rd one the one with ibuprofen for SLE and the urinalysis had eosinophils ? that happens only in TIN... but then again i cant recollect all 200... so not sure... type it out.. coz while she had lupus...the pathology was not due to lupus in her kidney... the pathology was due to taking ibuprofen for the pain and her getting TIN coz of it... u need to mention the full stem.. well atleast that was one question...not sure if that was the one you asked...
 
Anyone up for helping me with a couple of Qs?

1. Man has Cushing's syndrome. Low ACTH, high cortisol. What will happen to ACTH and cortisol after low-dose dexamethasone suppression test? Arrows for ACTH either going up or no change, and cortisol up, down or no change.

2. Girl has chronic cough with thick sputum, abdominal cramps in RLQ, and frequent resp infections. Clubbing of fingers, hyperresonance on chest percussion. Diffuse crackles and scattered wheezes. On xray - diffuse hyperinflation of the right upper lobe. She has a healthy brother. What's the likelihood he is a carrier for the condition.

3. Woman with lupus and nephritic syndrome. What would be on the renal biopsy?
a) crescent shaped glomeruli
b) inflamatory infiltrates in the interstitium
c) mesangial cell proliferation
d) sclerosed glomeruli
e) subepithelial deposits


Thanks))
btw what did u score ?
 
1. An 8 year old girl is brought to the physician by her mother because of a 3 week history of poor feeding chronic diarrhea and pale foul smelling stools.
Mother says the symptoms began with colicky abdominal pain following introduction of solid food to the infant;s diet. There is hsitory of gluten senstivity. She is 60th percentile and 25th percentile for length and weight.
P/E Normal

Which cell is dysfunctional:
a. enterocyte
b. goblet
c. paneth (x incorrect)
d. parietal
e. serosal
 
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Sorry about that, I thought we were supposed to paraphrase the questions.

A 45 year old man comes to the physician because of an enlarging face shoulders and trunk and thinning of his arms and legs. Physical examination shows a large plethoric face, fat pad over the upper thoracic spine and purple striae on the abdomen. Serum studies show undetectable ACTH and an increased cortisol concentration. Administration of low dose dexamethasone would most likely result in which of the following sets of serum findings?
a)ACTH up, cortisol up
b)ACTH up, cortisol no change
c)ACTH up, cortisol down
d)ACTH no change, cortisol up
e)ACTH no change, cortisol no change
f)ACTH no change, cortisol down

And the one about the woman, you're right. I totally misread the whole question. Thanks for pointing that out. And thanks for the genetics answer (I didn't take into account that we only look at the healthy ones)
 
Sorry about that, I thought we were supposed to paraphrase the questions.

A 45 year old man comes to the physician because of an enlarging face shoulders and trunk and thinning of his arms and legs. Physical examination shows a large plethoric face, fat pad over the upper thoracic spine and purple striae on the abdomen. Serum studies show undetectable ACTH and an increased cortisol concentration. Administration of low dose dexamethasone would most likely result in which of the following sets of serum findings?
a)ACTH up, cortisol up
b)ACTH up, cortisol no change
c)ACTH up, cortisol down
d)ACTH no change, cortisol up
e)ACTH no change, cortisol no change
f)ACTH no change, cortisol down

And the one about the woman, you're right. I totally misread the whole question. Thanks for pointing that out. And thanks for the genetics answer (I didn't take into account that we only look at the healthy ones)

No problem...you are welcome..
Can u please comment on one thing for me: I have not taken any NBME other than this one recently.. and hence don't knw how this compares..
I mean.. did u take any recently ? If so could u maybe let me know if your score on 18 and the other one were close... I know for a fact that 16 is very predictive.. just wanted to make sure this was not like a false positive or something..

Also... any idea about the question i posted above... gluten ? is it entero ?
Btw.. i got the Cushing's wrong too..
Page 618 goljan.. answer would be E.. I made many mistakes here and i think i could have done much better had i been a bit more prepared and better rested.. nonetheless... its a easy question.. Basically, Low Dose = Suppresses no type of cushings (Pit, Adrenal, ectopic)... high dose supresses ONLY pituitary and nothing else..

Input on the gluten one posted above will be VERY appreciated..since noone has taken this and getting the right answer is tough and also input on the following is VERY appreciated... (next comments)

Thanks
 
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2. An 82 year old woman comes to the physician because of constant severe lower abdominal pain and fever for 24 hours. Laproscopic examination shows severe diverticulosis and perforated diverticulitis. In spite of appropriate therapy she dies 2 days later. Her liver autopsy was given
Which of the following is the primary component of the material shown on the hepatic surface >

Collagen 1 (wrong)
Collagen 3
Fibrin
Fibronectin
Proteoglycans
 
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Looks like bacterial crap , probably fibrin since this would form an abscess eventually?
 
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In a study designed to test the effectiveness of a new drug in the treatment of endometriosis, 100 women randomly assigned to one of two groups.
48 of women receive new drug
52 receive standard therapy
The primary purpose of this method of assigning patients to different groups is to create which of the following ?

A Double blind study
B Single blind study
C Two group with similar sample size
D Two groups with similar underlying characteristics
 
For the last knee joint question, that is a uric acid crystal right there!

For the ACTH and Cortisol Q, no change no change
 
For the PKD question
Patient has CKD, going into renal failure, hence metabolic acidosis and compensatory decrease in Pc02.
Option A
 
In a study designed to test the effectiveness of a new drug in the treatment of endometriosis, 100 women randomly assigned to one of two groups.
48 of women receive new drug
52 receive standard therapy
The primary purpose of this method of assigning patients to different groups is to create which of the following ?

A Double blind study
B Single blind study
C Two group with similar sample size
D Two groups with similar underlying characteristics


Answer is D
 
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2. An 82 year old woman comes to the physician because of constant severe lower abdominal pain and fever for 24 hours. Laproscopic examination shows severe diverticulosis and perforated diverticulitis. In spite of appropriate therapy she dies 2 days later. Her liver autopsy is here:
Which of the following is the primary component of the material shown on the hepatic surface >

Collagen 1 (wrong)
Collagen 3
Fibrin
Fibronectin
Proteoglycans

Fibrin
 
1. An 8 year old girl is brought to the physician by her mother because of a 3 week history of poor feeding chronic diarrhea and pale foul smelling stools.
Mother says the symptoms began with colicky abdominal pain following introduction of solid food to the infant;s diet. There is hsitory of gluten senstivity. She is 60th percentile and 25th percentile for length and weight.
P/E Normal

Which cell is dysfunctional:
a. enterocyte
b. goblet
c. paneth (x incorrect)
d. parietal
e. serosal
enterocyte
 
I know the answers to these
I want explanations please

1. 48 year old female with a history of CA breast who received 4week course of radiations 6 months ago comes for followup. Exam. shows no CA recurrence. R/R 26/min. CT chest shows b/l atelectasis in upper lung fields. Primary pathophysiological cause is?

A- Compression
B- Consolidation
C- Contraction
D- Obstruction
E- Resorption

2. A 35 yr old woman has congestive cardiomyopathy and pitting edema. Her serum urea nitrogen concentration is 25mg/dl and serum creatinine is 1.8mg/dl. Furosemide therapy is started. After 5 days, labs show

Na 130
K 4.5
Cl 90
HCO 30
(all in mEq/L)

BUN 85mg/dL
Creatinine 2.2mg/dL
Albumin 3g/dL

Urine
specific gravity 1.023
rbc 0
wbc0
sediment none

Urinary fractional excretion of sodium is less than 1%. What is the most likely explanation?

A Acute tubular necrosis
B Diabetic nephropathy
C Glomerulonephritis
D Hepatorenal syndrome
E Nephrogenic DI
F Osmotic Diuresis
H Prerenal azotemia
I Renal artery stenosis
 
I know the answers to these
I want explanations please

1. 48 year old female with a history of CA breast who received 4week course of radiations 6 months ago comes for followup. Exam. shows no CA recurrence. R/R 26/min. CT chest shows b/l atelectasis in upper lung fields. Primary pathophysiological cause is?

A- Compression
B- Consolidation
C- Contraction
D- Obstruction
E- Resorption

2. A 35 yr old woman has congestive cardiomyopathy and pitting edema. Her serum urea nitrogen concentration is 25mg/dl and serum creatinine is 1.8mg/dl. Furosemide therapy is started. After 5 days, labs show

Na 130
K 4.5
Cl 90
HCO 30
(all in mEq/L)

BUN 85mg/dL
Creatinine 2.2mg/dL
Albumin 3g/dL

Urine
specific gravity 1.023
rbc 0
wbc0
sediment none

Urinary fractional excretion of sodium is less than 1%. What is the most likely explanation?

A Acute tubular necrosis
B Diabetic nephropathy
C Glomerulonephritis
D Hepatorenal syndrome
E Nephrogenic DI
F Osmotic Diuresis
H Prerenal azotemia
I Renal artery stenosis

1. radiation causes scar which causes contraction

2. CHF, CRF and Hepatic failure all cause decrease in EABV as such and giving furosemide will just increase that... also the kidneys seem to be doing pretty good...the functional capacity seems to be intact... seen via SG 1.023, FeNA < 1%
I dont see how it could be any of the other ones... its pretty straightforward prerenal azotemia because of decreased EABV.. all CHF patients have that due to water and Na+ retention in the third space
 
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I think i was brain dead in many of these questions.. was up like 40 hours or so..

please can u tell me how the score of this test compares to your previous ones ?
i got a good score but dont know what to make of it... as it seems as though if i had slept well and studied FA end to end just once (which takes me 12 hrs).. then i calculated a minimum of 9 more correct..

Did u score higher in this NBME than in previous ones by a significant margin ? @AnxietyAnnie ?
 
1. radiation causes scar which causes contraction

2. CHF, CRF and Hepatic failure all cause decrease in EABV as such and giving furosemide will just increase that... also the kidneys seem to be doing pretty good...the functional capacity seems to be intact... seen via SG 1.023, FeNA < 1%
I dont see how it could be any of the other ones... its pretty straightforward prerenal azotemia because of decreased EABV.. all CHF patients have that due to water and Na+ retention in the third space
Can you please explain in detail? What's EABV? The only reason I picked out pre renal azotemia was due to BUN/Cr and FeNA<1.
 
I overthink too much.. i thought they have hyperreninemic hypertension and hence low H+ and low K+
Don't overthink! It can destroy your score even if you have a sound knowledge base. I do it too! The answers I got wrong are so silly that even I am judging myself. lol

I scored 2 points lower in 18 than my last nbme. I have only taken one other.
Nbme 17 -249(3weeks ago)
Nbm2 18- 247(2 days ago)

I have 3 weeks left till my exam. Can you give me any pointers on how to study? I want to break 250.
 
Can you please explain in detail? What's EABV? The only reason I picked out pre renal azotemia was due to BUN/Cr and FeNA<1.
Both of those are the exact reasons you should have chosen that answer.. you are right..

EABV = effective arterial blood volume...
its low in CRF, CHF and hepatic failure.. if u have goljan...look it up..its a good concept worth knowing.. its in inital chapters.. i think 4th or something chapter..

As far as advise, sleep well day before exam and if possible dont study day before exam... just relaax...know FA word for word with explanation... work on ur weaknesses... that u can identify only via your score card on nbme.... do anatomy well..and do all nbmes...even retired as questions can repeat

I still have a while to go..like over s month.. i intend on taking in may before the pool changes... in early may or late april...
 
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@weed
Both of those are the exact reasons you should have chosen that answer.. you are right..

EABV = effective arterial blood volume...
its low in CRF, CHF and hepatic failure.. if u have goljan...look it up..its a good concept worth knowing.. its in inital chapters.. i think 4th or something chapter..

As far as advise, sleep well day before exam and if possible dont study day before exam... just relaax...know FA word for word with explanation... work on ur weaknesses... that u can identify only via your score card on nbme.... do anatomy well..and do all nbmes...even retired as questions can repeat

I still have a while to go..like over s month.. i intend on taking in may before the pool changes... in early may or late april...
thank you and goodluck for your exam!! I see you breaking 270!
 
Hello everyone, took it yesterday, test in a week O.O Only took this one, so I can't say if it predicas similar to the other NBMEs

Question (section 1, question 19/50):
60-yo man comes for routine health examination. He has had normal blood pressure measurements. His blood pressure today is 170/95mmHg. Physical examination shows no other abnormalities. Serum studies show hypokalemia and metabolic alkalosis. Plasma renin activity and serum adosterone concentrations are increased. Following the administration of captopril, there is a marked increase in plasma renin activity. Which of the following is the most likely cause of the findings in this patient:

a) aldosterone-secretin adrenal tumor (INCORRECT)
b) chronic glomerulonephritis
c) Cushing sd
d)essential hypertension
e) renal artery stenosis


Thank you all!
 
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E) RAS . Captopril --> Removes the AT effect from efferent arteriole --> Reduces GFR --> Kidney ''senses'' that and secretes more Renin
 
Thank you @AnxietyAnnie !

more questions:

Section 2, item 39/50
36yo woman comes to the physician because of a 2 week history of fatigue, bleeding of the gums, and bone pain. Physical examination shows pallor, hepatoesplenomegaly, and ecchymotic lesions over the extremities. Labs:
Hb 8g/dl
Ht 25%
Leukocytes: 36,000
segm neutr 4%
eosinophils 4%
lymph 6%
mono 6%
promielo 80%
platelets 25,000

Polymerase chain reaction test shows an mRNA crresponsing to the retinoic acid receptor- alfa/promyelocytic leukemia fusion gene resulting from a reciprocal translocation of chromossomes 15 and 17. Treatment w/ all-trans retinoic acid is started. In response to the therapy, the fusion protein will most likely attract which of the following pronteins to form a pre-transcriptional complex?
a)histone acetylase
b)histone kinase
c) histone N-methyltransferase
d) nitric oxide
e) protein kinase A (incorrect)


section 1, question 13/50

25 yo mand who has a history of facial flushing and rapid heart rate each time he consumes a small amount of alcohol participates in a study of alcohol intolerance. colecular analysis shows the presence of a lysine (K487, oriental variant) for glutamate (E487, native variant) substitution in aldehyde dehydrogenase. the kinetic characteristics of the enzyme variants are shown:
Enzyme Km (NAD+)microM Kcat (min-1)
E487 37 180
K487 5600 9.5
based on these findings, which of the following is the most likely cause of this man's condition?
a) decreased catalyitic efficiency of K487
b)increased catalytic efficiency of E487
c) less rapid turnover by E487
d) more rapid turnover by K487
e)tigher binding of NAD+ to K487
f) weaker binding of NAD+ to E487 (incorrect)

Thanks!
 
@pedMDbra

ATRA will induce differentiation---> Increased transcription----> Histone acetylation---> ans is A

For the alcohol question, answer is A as well. He is experiencing those symptoms because of decreased activity of the oriental variant.
 
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Hi guys just signed up. Took nbme 18 yday had 241. nbme 15 last month 234. I wasnt too bad but i think it was tougher than 15. Exam in 4days
 
@pedMDbra what is question i s testing is the fact that the mutant allele should have a lower affinity(higher) km for alcohol. Taking that into consideration answer is A.
 
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2. An 82 year old woman comes to the physician because of constant severe lower abdominal pain and fever for 24 hours. Laproscopic examination shows severe diverticulosis and perforated diverticulitis. In spite of appropriate therapy she dies 2 days later. Her liver autopsy was given
Which of the following is the primary component of the material shown on the hepatic surface >

Collagen 1 (wrong)
Collagen 3
Fibrin
Fibronectin
Proteoglycans

Fibrin. Perf'd diverticuli = poop in belly = tons of inflammation = fibrin.

Thank you @AnxietyAnnie !

more questions:

Section 2, item 39/50
36yo woman comes to the physician because of a 2 week history of fatigue, bleeding of the gums, and bone pain. Physical examination shows pallor, hepatoesplenomegaly, and ecchymotic lesions over the extremities. Labs:
Hb 8g/dl
Ht 25%
Leukocytes: 36,000
segm neutr 4%
eosinophils 4%
lymph 6%
mono 6%
promielo 80%
platelets 25,000

Polymerase chain reaction test shows an mRNA crresponsing to the retinoic acid receptor- alfa/promyelocytic leukemia fusion gene resulting from a reciprocal translocation of chromossomes 15 and 17. Treatment w/ all-trans retinoic acid is started. In response to the therapy, the fusion protein will most likely attract which of the following pronteins to form a pre-transcriptional complex?
a)histone acetylase
b)histone kinase
c) histone N-methyltransferase
d) nitric oxide
e) protein kinase A (incorrect)


section 1, question 13/50

25 yo mand who has a history of facial flushing and rapid heart rate each time he consumes a small amount of alcohol participates in a study of alcohol intolerance. colecular analysis shows the presence of a lysine (K487, oriental variant) for glutamate (E487, native variant) substitution in aldehyde dehydrogenase. the kinetic characteristics of the enzyme variants are shown:
Enzyme Km (NAD+)microM Kcat (min-1)
E487 37 180
K487 5600 9.5
based on these findings, which of the following is the most likely cause of this man's condition?
a) decreased catalyitic efficiency of K487
b)increased catalytic efficiency of E487
c) less rapid turnover by E487
d) more rapid turnover by K487
e)tigher binding of NAD+ to K487
f) weaker binding of NAD+ to E487 (incorrect)

Thanks!

I also got the AML question wrong...I'm now 90% sure the answer is histone acetylase. The giveaway is "pre-transcriptional complex," meaning histones need to be acetylated in order to start transcribing genes to differentiate the neoplastic cells.

The enzyme kinetics question answer is A. This is pretty straightforward biochemistry. Km is the substrate concentration required for an enzyme to reach 1/2 Vmax; higher Km means weaker substrate binding affinity- this rules out choices E and F, since those choices are backwards. Kcat is the the turnover constant- how much substrate can the enzyme chew through under max saturation. Higher Kcat = more enzymatic reactions per second. That rules out C and D, since these are also backwards. So now it's down to A and B; A is the obvious answer to what's causing this guys symptoms.
 
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