NBME#3 block 2 Q1----------------------Q50 - maryam2009

[ArchivalUser]

16--i had saved this explantion --always thankful to him for this explanation!

sarim explained it extremely well as the following.....

Conditional Probability:....

If given that the pt survived say like 1 yr( or 2 yrs etc.) and asking for probability of surviving certain # of yrs (e.g 2 yrs or 3 yrs etc.).

and the data is given in one of these two ways:

.....STRAIGHT SURVIVAL.

0--1 yr = 80 %
0--2 yr = 60 %
0--3 yr = 40 %
0--4 yr = 20 %

say like if pt survived 1 yr what would be the probability--?(in this case u DIVIDE probabi)

DIVIDE by (prob.of # yr pt already survived e.g. 1 yr)

probability of surviving 2 yrs.......60/80 =75%
probability of surviving 3 yrs.......40/80 =50%
probability of surviving 4 yrs.......20/80 =25%

if the pt survived say like 2 yrs and probability of surviving 4 yrs?
20/60 =33 %

.......SURVIVING THIS INTERVALE.

0--1 yr = 80%
1--2 yr = 60%
2--3 yr = 40%
3--4 yr = 20%

say like if pt survived 1 yr ,what would be the probability? (in this case MULTIPLY probabil.)
Note: Multiply probabilities in between(SKIPPING the survived yr probability in this case 80%)

probability of surviving 3 yrs = 60 times 40
probability of surviving 4 yrs = 60 times 40 times 20

If asked probability of surviving straight say like 4 yrs(from the day one without condition of already survived certain # of yr) = multiply all probabilities 80 times 60 times 40 times 20

NOw in NBME 3 bloc 2, 16 answer is D
0.875 times 0.9 times 0.9

B- would have been the answer if asked straight 4 yr survival
C- is the probability of surviving 3 yrs once the pt already survived for 1 yr

sarim explained it extremely well.....

[ArchivalUser]

q 17-cc
explanation awaited

[ArchivalUser]

q 18-Bb

Disorder or Condition ----------------Platelet Count--------- BT-------- PT--------- PTT

Thrombocytopenia ITP, TTP, HUS-- -------↓----------------- ↑---------Normal---- -Normal

Von Willebrand disease ------------------Normal ------------↑ ----------Normal------- ↑

Hemophilia A ----------------------------Normal----------- Normal ------Normal -------↑

DIC -------------------------------------↓ -----------------↑------------ ↑ ---------↑

Primary fibrinolysis -------------------Normal-------------- ↑-------------- ↑ -----------↑

Aspirin or NSAID use----------------- Normal------------ ↑ ------------Normal---- Normal

Warfarin or heparin use --------------Normal -------------Normal---------- ↑---------- ↑

[ArchivalUser]

q 19= dd

[ArchivalUser]

As splenectomy causes an increased risk of overwhelming sepsis due to encapsulated organisms (such as S. pneumoniae and Haemophilus influenzae)

the patient should receive the pneumococcal conjugate vaccine (Prevnar),
Hib vaccine, and the meningococcal vaccine; . These bacteria often cause a sore throat under normal circumstances but after splenectomy, when infecting bacteria cannot be adequately opsonized, the infection becomes more severe.

An increase in blood leukocytes can occur following a splenectomy.The post-splenectomy platelet count may rise to abnomormally high levels (thrombocytosis), leading to an increased risk of potentially fatal clot formation. There also is some conjecture that post-splenectomy patients may be at elevated risk of subsequently developing diabetes.
Splenectomy may also lead to chronic neutrophilia. Splenectomy patients typically have Heinz bodies in their blood smears

[ArchivalUser]

20==ee
amyotrophic lateral dystrophy,,

[ArchivalUser]

gd one for 18 drona ...thnx

[ArchivalUser]

21.C

It is critical that this condition be diagnosed and corrected at an early age since children with uncorrected strabismus may go on to develop amblyopia.

Amblyopia means that visual stimulation either fails to transmit or is poorly transmitted through the optic nerve to the brain for a continuous period of time. It often occurs during early childhood, resulting in poor or dim vision. Amblyopia normally affects only one eye, but it is possible to be amblyopic in both eyes if both fail to receive good, clear visual images. Detecting the condition in early childhood increases the chance of successful treatment.

Amblyopia is a developmental problem in the brain, not an organic problem in the eye (although organic problems can give rise to amblyopia which continue to exist after the organic problem has resolved).The part of the brain corresponding to the visual system of the affected eye is not stimulated properly and develops abnormally.

[ArchivalUser]

22.concentration C
The resting membrane potential is very sensitive to the extracellular potassium .Hyperkalemia depolarizes and hypokalemia hyperpolaraizes cells

[ArchivalUser]

23.C
Epidural hematoma....lucid interval due to rupture of Middle meningial Artery(branch of Maxillary artey). CT shows biconcave disk and often with fracture of Temporal one.
http://www.google.com/imgres?imgurl=http...CCAQ9QEwBA