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NBME Explanations

NBME 17 Questions and Answers

Discussion in 'USMLE Step 1' started by orthopod, May 24, 2015.

  1. Lenka Penka

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    I can see this could be the correct answer since the patient had occult blood in his stool, so it could have been an adenomatous polyp, yet the determination of whether it's tubular or villous is done histologically- so it's very strange the answer refers to a histologic description.
     
  2. Lenka Penka

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    According to the 2016 First Aid- HOCM is associated with MITRAL regurgitation due to impaired mitral valve closure (page 291).
    Wikipedia also agrees.
     
  3. Lenka Penka

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    You're probably right. There are curtain phisiologic changes during pregnancy:
    - Thyroid hormone-binding globulin (TBG) excess results in high serum total T4 and total T3 concentrations but not high serum free T4 or free T3 concentrations.
    - High serum human chorionic gonadotropin (hCG) concentrations during early pregnancy and even higher concentrations in women with hyperemesis gravidarum or multiple pregnancies may result in transient subclinical or rarely overt hyperthyroidism.

    Source- UpToDate
     
  4. Lenka Penka

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    Explanation:
    Human chorionic gonadotropin (hCG) has the biologic activity of LH but a longer half-life in the circulation; it stimulates the Leydig cells of the testes to synthesize and secrete testosterone. hCG is used to replace LH in men who have secondary hypogonadism and desire to become fertile.
    Human chorionic gonadotropin (hCG), while not an androgen, stimulates the testes to make testosterone and is especially useful in stimulating both testosterone and sperm production. (UpToDate)
    I assume that if hCG reaches high levels and there is excess testosteron produced, aromatase in the testis converts it to Estradiol.
    If anyone has futher knowledge, please share.
     
  5. orthopod

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  6. orthopod

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    Are you suggesting the listed answer is incorrect?
     
  7. orthopod

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    Sudden death could also occur in AS, as in the elderly population. Severe AS has been linked to arrhythmias such as Vtach. Did you get this answer correct on your form?
     
  8. Rana

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    I'm all late but maybe this could help someone. I got the answer correct on my form: Aortic Stenosis.

    LV concentric hypertrophy is due to pressure overload; think of chronic hypertension or [age-related] aortic valve stenosis.
     
  9. orthopod

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    Yeah, I figured. Thanks for the confirmation
     
  10. Mehmed

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    Thankyou so much
     
  11. SaharKh

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    Please anyone can explain this question. Thanks in advance

    24. Rndomized controlled study of 2000 patients with insomnia is conducted to evaluate the efficacy of a new medication to treat this condition. Ten subjects from both the control and treatment groups do not complete the study are are not included in the analysis. Treatment group able to fall asleep 5 minutes faster than control (p=0.001). Neither group report an improvement in quality of life. Conclude that new med is efficacious in treating insomnia. Type of error?
    - Failure to distinguish between statistical significance and clinical significance
     
  12. orthopod

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    Great question. Stats is a major topic, and it comes up on every single USMLE. You need to make sure you're comfortable with it, as it's easy points you don't want to miss.

    As for your specific question - You need to differentiate statistical significance from clinical significance.
    Statistical significance: Based on the results from the data. When alpha (p value) is < 0.05, we term that result, "statistically significant." What this means is that we can be more than 95% certain that the difference between the two sets of data was not due to chance.
    Example: comparing the height of your classmates, between males and females. You hypothesize that there is no difference between gender. Then, you take Avg of male height and Avg of female height in your class. With a few fancy tests (not relevant here), you find there is a difference between males and females, and the p value is 0.04. This tells us that we are more than 95% confident this difference between males and females was not due to chance. On the other hand, if the p value was 0.1, we cannot conclude there was a statistically significant difference, and the difference we found may be due to chance.

    Clinical significance: Even if there is a statistical significance, does it clinically matter?
    In the example in the question, we see that there is a statistical difference between subjects and control (p < 0.05), but they only fall asleep 5 minutes faster, and there is no improvement in quality of life. So even if you fall asleep sooner, it doesn't affect any outcomes, so who cares? Thus, no difference clinically.
     
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  13. SaharKh

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    Thank you so much! Really helpful.
     
  14. jjb

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    TPMT question - "They may be given normal doses of 6-MP" is incorrect.
     
  15. Subrina Sundil

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    here,3.100=300.
    now 300.100/45=15%
     
  16. ChinaPaw

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    Hi, Mark:
    The related possible questions in the answer section are really good, but there are no answers provided, and some of those related questions are equally hard and tricky. Since there is a high chance that the interviewer is going to task those related questions, will you provide answers to them?
     
  17. ChinaPaw

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    Hi, Mark:
    The related possible questions in the answer section are really good, but there are no answers provided, and some of those related questions are equally hard and tricky. Since there is a high chance that the interviewer is going to task those related questions, will you provide answers to them?
     
  18. ChinaPaw

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    Hi, Mark:
    The related possible questions in the answer section are really good, but there are no answers provided, and some of those related questions are equally hard and tricky. Since there is a high chance that the interviewer is going to task those related questions, will you provide answers to them?
     
  19. ChinaPaw

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    Hi, Mark:
    The related possible questions in the answer section are really good, but there are no answers provided, and some of those related questions are equally hard and tricky. Since there is a high chance that the interviewer is going to task those related questions, will you provide answers to them?
     
  20. ChinaPaw

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    Hi, Mark:
    The related possible questions in the answer section are really good, but there are no answers provided, and some of those related questions are equally hard and tricky. Since there is a high chance that the interviewer is going to task those related questions, will you provide answers to them?
     

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