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Old 03-01-2012
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Arrow NBME 3 Block 3 discussion

Q31:
This is A, key is wrong. Central (diaphragmatic) sleep apnea occurs in the elderly, overweight and has cheynne stoke breathing. In the stem they describe cheynne stoke breathing. In obstructive sleep apnea they would describe a middle aged overweight individual who snores.

Q32:
A little confused here, I picked A. Because of the ductus the blood is completely bypassing the the left side. But when the ductus closes then blood is delivered to the LA to increase its pressure. The answer key says C, and I see how than can happen too. Which one is the better answer???

Q39:
The right answer is C.
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Qs 31 well the Qs says the diaphragm had movement during the episodes this is the main feature of OSA not central .. this statement is to differentiate the two ...... see FA in resp system .. pg 512 in my FA..

Qs 32 C is the only ans i feel , becoz its actually asking when the child takes breath the pulmonary resistence fall and LA pressure increases and closes foramen ovale .... if you see the foramen ovale passes good amount of blood to LA and only the left out blood passes from Ductus to aorta ...so even after the closure of DA there is no significant increase in LA blood flow as the blood from foramen ovale has stopped and is now entering directly by pulmonary veins ... yes even i had thought about DA if it could be the ans but felt C was better ....

Qs 39 yes C is right ......

need help with

Qs 1 I really dont get these procedures ?? how do you do them ?

QS 49 .... did not get it ......
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Quote:
Originally Posted by Hitman View Post
Qs 1 I really dont get these procedures ?? how do you do them ?
Hybridization: attaching a small complementary nucleic acids via DNA or RNA probe....scanner then detects relative amounts of complementary binding. Could be used but since only dealing with small segment will not be accurate for the entire DNA.

Northern Blotting: Used to detect gene expression...ie. RNA. Not useful here cause we want to look at DNA.

PCR: Used to amplify (make multiple copies) of a desired fragment of DNA. Not useful here cause we want to compare not make copies.

Restriction Enzyme Analysis: An enzyme that attaches to a specific neucleotide sequence. Not useful here as once again we want to take a look at the entire DNA not a particular segment.

Neucleotide Sequencing: Very time consuming process but will give you the entire sequence of the DNA. Then you can compare the 2 strands and see how similar they are. The most accurate as covers the entire DNA.


Quote:
Originally Posted by Hitman View Post
QS 49 .... did not get it ......
2 ways to do this.

First use either rough approximation. It's good if you know what you're looking for. You could say it's a type of skewed distribution with the tail on the left. Right off the bat you know median is bigger than the mean. Then if you take a look at the readings there are 2 of them with 1.0. So that's the mode and then you can tell the median is bigger than the mode as well. Rules out all the other answers and you get B.

OR

Secondly just calculate it.

Mean: 1.73
Mode: most freq. value = 1.0
Median: mid pt. 50th percentile = 2.5
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I used the same method , the tail to the left and so selected D mode greater than median ... i thought mode is the one with the largest number like 10 , but it seems to be the one with the largest frequency ??? so are you counting 1 and 10 as same becoz you said there are 2 of them with 1.0??

becoz if its negatively skewed then even D appears correct ???
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Old 03-02-2012
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Quote:
Originally Posted by Hitman View Post
I used the same method , the tail to the left and so selected D mode greater than median ... i thought mode is the one with the largest number like 10 , but it seems to be the one with the largest frequency ??? so are you counting 1 and 10 as same becoz you said there are 2 of them with 1.0??

becoz if its negatively skewed then even D appears correct ???
yeah but that's where they threw in the trick.

Usually Mode is bigger than the median in tail to the left skew. But since they are showing you the actual values you can see what the mode is. Yeah mode is the value that occurs the most which is 1.0 as it occurs 2 times (every other value only occurs once). So this case is the exception like everything on step 1 .


So if you know what you were looking for you could solve it in 10 seconds.

1. Skew to the left so you know right away the mean is the smallest value.
2. Mode is 1.0 so you know that median is bigger than both mean and mode.
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sorry still not getting it ..... i arranged the numbers in the order

0.5 , 0.5 , 0.6 , 0.75 , 1, 0.9 , 1 , 2.5 , 4 , 5.5 ....

got mean as 1.725 , mode yes 1 as it has come 2 times ...

but the median i got as 1 .... as add 1 and 0.9 and then divide by 2 ...

so i get A as the ans ..... do tell me how did you get the median 2.5 ??
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so I've been thinking about this for a while....I think the right answer is A now.

It's not a negative skew....if anything it's a positive skew cuz most of the values are smaller and bunched together and then 3 of them are so far out making the tail go to the right.

Regardless you don't even have to se the distribution.

Just by calculating the tendencies

Mean = about 1.5
Mode = 1.0 (most freq value)
Median = Like you said it will also be 1.

So mean > mode=median

A is the only answer that fits.
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Ya Q49th answer is A.I picked that due to above explanation
I have doubt
Q28 in this question the key i have give answer as SLE now i know there are skin rash and thrombocytopenia favoring it but it clearly mention here that WBC IS INCREASED if it was SLE it should have been neutropenia or lymphiopenia also usually SLE is not a monoarticular disease...
Increase in leukocyte count here does favors an infectious cause hence I think it should have been Gonococcal infection the most common cause of monoarticular arthritis??

Also in 42 the key i have gives it as A I think it should have been D since increase in BP chronically will lead to decrease in renin and hence angiotensin and aldosterone??

Also can someone explain to me Q7?? and Q15??
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Quote:
Originally Posted by mohitkmc View Post
Ya Q49th answer is A.I picked that due to above explanation
I have doubt
Q28 in this question the key i have give answer as SLE now i know there are skin rash and thrombocytopenia favoring it but it clearly mention here that WBC IS INCREASED if it was SLE it should have been neutropenia or lymphiopenia also usually SLE is not a monoarticular disease...
Increase in leukocyte count here does favors an infectious cause hence I think it should have been Gonococcal infection the most common cause of monoarticular arthritis??

Also in 42 the key i have gives it as A I think it should have been D since increase in BP chronically will lead to decrease in renin and hence angiotensin and aldosterone??

Also can someone explain to me Q7?? and Q15??
Q7:
Gliosis is reponse to injury in the brain (also in FA), so glial cells will be present. Fibroblasts and Myofibrobalsts are not present in the brain. Ependymal cells are in ventricles and die due to injury. There are no neutrophils in the brain tissue.

Q15:
They tell you in the stem, increased incidence of autoimmune disease. This means that there are self reacting lymphocytes. FAS gene is important for apoptosis. A defect means there will be no clonal deletion of T cells in the Thymus that react to self antigens. Hence more autoimmune disease.

Q28:
Rash on cheek, joint pain, mouth ulcers, decreased platelets and RBC. Increased WBCs (means there is increased production of immunoglobulins). This is classic SLE, can be nothing else. Look in FA, it lists all the symptoms and these are all there.

Q42:
yes he has increased BP but you're missing the main point. Bruits over both renal arteries, means stenosis in both (most probably due to atherosclerosis). This is decrease RPF which will cause increased Renin leading to increased angiotensin and aldosterone. His raised BP is because of this stenosis.
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Quote:
Originally Posted by haga View Post
Q7:
Gliosis is reponse to injury in the brain (also in FA), so glial cells will be present. Fibroblasts and Myofibrobalsts are not present in the brain. Ependymal cells are in ventricles and die due to injury. There are no neutrophils in the brain tissue.

Q15:
They tell you in the stem, increased incidence of autoimmune disease. This means that there are self reacting lymphocytes. FAS gene is important for apoptosis. A defect means there will be no clonal deletion of T cells in the Thymus that react to self antigens. Hence more autoimmune disease.

Q28:
Rash on cheek, joint pain, mouth ulcers, decreased platelets and RBC. Increased WBCs (means there is increased production of immunoglobulins). This is classic SLE, can be nothing else. Look in FA, it lists all the symptoms and these are all there.

Q42:
yes he has increased BP but you're missing the main point. Bruits over both renal arteries, means stenosis in both (most probably due to atherosclerosis). This is decrease RPF which will cause increased Renin leading to increased angiotensin and aldosterone. His raised BP is because of this stenosis.
@Haga:Refer to Pg 44 on goljan RRS in hematology findings of SLE it says thay its AIHA,Thrmbocytopenia and lymphonenia and involment of small joints is more common..Now I know above Question is trying to trick us by giving abt rash definitely its of SLE I also thought abt it but the increase in LEUKOCYTE count with classical knee joint involvement can favor towards GONOCOCCAL INFN they can occur in an SLE pt...the trick is the increase in count so thats why i think it should have been gonococcal....

Thanks abt above explanations in Q42 they were smart to fool me lol never made notice of bruit which makes a lot of sense I hope I dont get fooled like this in exam.
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Quote:
Originally Posted by mohitkmc View Post
@Haga:Refer to Pg 44 on goljan RRS in hematology findings of SLE it says thay its AIHA,Thrmbocytopenia and lymphonenia and involment of small joints is more common..Now I know above Question is trying to trick us by giving abt rash definitely its of SLE I also thought abt it but the increase in LEUKOCYTE count with classical knee joint involvement can favor towards GONOCOCCAL INFN they can occur in an SLE pt...the trick is the increase in count so thats why i think it should have been gonococcal..
Rash on the cheeks
INTERMITTENT joint pain
mouth ulcers

This is a classic description of an autoimmune disorder.


Gonococcal arthritis occurs when gonorrhoea becomes systemic. There would be high fever due to sepsis, CONTINUOUS joint pain with inflammation, some sort of sexual organ symptoms as well. This is not the type of history for gonococcal arthritis.
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