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Thursday, May 10, 2007

The Day Before the Exam Is High Yield for the USMLE

Sounds weird but I think its true. The day before the exam you are at a set point to achieve for the day of the exam. The height of this set point is in direct relation to the amount and quality of effort you have put into the exam. The day before, you might be tempted to try to push that set point higher. I instead suggest to work on keeping the set point from dropping any lower, that is make it your duty to keep your set point stable. Don't harm your score by a little pre-test jiggers.

Make sure not to panic about any details you may not be able to remember. This exam won't be testing details as much as it will test your concepts. For example, the day(s) before the exam you might close your eyes and try to recall all you know. Some people report having a feeling of emptiness but do not panic; No one will be asking you to give a lecture on any of this stuff but only to circle the best answer. Please, DO NOT FREAK YOURSELF OUT THE DAY BEFORE THE EXAM as that is low low yield and this is a high yield blog.

This is not to say you should go into denial about tomorrow. Forcing yourself to not think about the exam on the day before is about as or more stressful as studying another day. I tried to keep my day before the exam as stress free as possible so that I could be relaxed and most importantly confident on test day. In order to keep yourself focused on the exam I have a simple solution and here it is. The day before I would do NBME questions that you have already answered and have figured out the correct answers. This will work to keep the concepts of the most important practice questions fresh but also it should further build up your self confidence as you'll probably score much more correct this time around.

Also note that I do not suggest that you do practice questions over and over again throughout your study period just to falsely build up your self confidence - to me (but many disagree and do fine their way) doing Q-bank more than once for whatever reason is a waste - how about you move on to USMLE World? All I'm saying is that a boost of self confidence the day before the exam is just what a 1st time boards test taker needs.

Sunday, May 6, 2007

The Tuberculous Granuloma is High Yield for the USMLE

Ahh the Granuloma - a great example of topic that overlaps multiple subjects and any topic that brushes borders with the likes of pathology, immunology and microbiology make for great questions. Here are 5 steps to the granuloma in perfect 3rd grader doodle form:

Step 1:
Inhale the red, ACID FAST rod

M. tuberculosis is only acid fast why?

B/c of the MYCOLIC ACID in the cell wall resists decolorization with acid-alcohol and so it remains red which is the color of the initial stain, carbol fuchsin.

What else stains acid fast? Nocardia which is “partially acid fast”

Step 2: Phagocytosis by alveolar macrophages

Circulating monocytes roll on the vascular endothelium (d/t selectins) and adhere to it (d/t ICAMs) and then transmigrate into the affected area where they are called tissue macrophages.

Macrophages are the main players in the formation of a granuloma

Step 3: Antigen Presentation

Step 4: T Cell Activation

CD4 T Cells are involved

The TH1 subtype

No CD4 T Cells? No Granuloma. AIDS patients who loose their CD4 t-cells well before loosing their CD8 T Cells will make very weak if any granulomas.

Step 5: Macrophage Activation

Did I mention what the main player of a granuloma is? Oh yea, its the macrophage.

The Caseous Granuloma

Note that the caseous necrosis is cottage cheese like and is due to the destruction of the M. TB organism's cell wall's mycolic acids (mycolic acids are lipids).

Saturday, May 5, 2007

Fundamentals of Biochemistry are High Yield for the USMLE

Sorry for the infrequent posting as of late but I've been traveling. Here's a great link if you are having trouble picturing the various molecular events not only in biochem and cell biology but also micro and immuno. It contains many animations that really helps you picture this stuff.

The page is called Max Animations

I especially suggest the lac operon, HIV virus lifecycle but there are tons of animations there so I just though I would point out this potentially useful link for you.

Thursday, May 3, 2007

Viruses are High Yield for the USMLE Step 1

I suggest when trying to memorize viral structures make a priority list. Common viruses and ones that also overlap with pathology are the ones to focus on here since they can be asked about in many different ways.

Knowing DNA vs RNA is the most important distinguishing feature. Furthermore, f you know if its DS or SS you'll probably get the points.

Enveloped vs Naked: If you can memorize enveloped vs. naked for each virus then god bless, but I like this:
Envelopes are made of a lipid bilayer which are prone to destruction by the environment whereas naked viruses are more resistant to environmental stresses.

A 46 year old female who has genital warts (d/t HPV) takes a shower in her home during which time the virus sheds on the floor. Later her child presents with a wart on his toe.
This all happened since this virus had its tough nucleocapsid for protection and not a wimpy envelope. Take home message is if the virus is capable of fomite transmission it is probably naked.

Play odds, especially for rare viruses with less of a chance of being asked. I walked into the exam knowing that if I saw an RNA virus that looked deadly or pretty rare I would guess that it is SS (-) linear w/envelope.

Here is my list of High Yield Viruses and why I think they have a great chance of being asked
  • Herpesviruses - DS linear DNA
    • this family includes so many viruses that overlap with pathology I list it first since I think this is most important.
  • All the viruses that cause hepatits - see First Aid for them since these are important!
    • Note that Hep B carries the reverse transcriptase enzyme with it just like the retroviruses do.
  • HIV - SS (+) linear RNA
    • If you don't get at least 1 question on AIDs I will give you my blog. Seeing if you know virus structure is a possible secondary question.
  • Papovavirus - DS (-) linear
    • besides HPV causing cervical cancer don't forget about molluscum contagiosum which causes the umbilicated wart (center of wart is depressed like an "innie" belly button).
  • Paramyxoviruses - SS (-) linear RNA with helical capsid symmetry
    • this family is responsible for causing croup (parainflunza virus), bronchiolitis (d/t RSV), measles and mumps.
  • Parvovirus - SS linear DNA
    • It, along with Hepadnavirus, is exception to the rule that all DNA viruses are linear.
    • It overlaps with pathology since it causes aplastic anemia in patients with sickle cell disease
      • Pt might give you a history of having recent contact with a kid who had a slapped cheek appearance.
      • Blood labs will give you a low RBC count with low reticulocytes (less than or equal to 3% of hematocrit - I wouldn't freak out about not knowing how to correct a reticulocyte count).
  • Influenza virus (an orthomyxovirus) - SS (-) linear segmented RNA
    • the NBME and practice questions I've seen love the fact that this genome is segmented since:
      • Genetic shift - if our influenza virus recombines with a pig's or chickens genome we get pandemics - we're all screwed (small minor mutations lead to drifts causing an epidemic in a much smaller area w/ much less people). involved)
      • If you digest the genome and view it with northern blotting you will see each of these (7 or 8) segments as separate bands.