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NBME 24 Answers

nbme24/Block 1/Question#1 (79.3 difficulty score)
A researcher hypothesizes that exposure to ...
Case-control studyπŸ”,πŸ“Ί
tags: clinical_trials medicine 

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 +15 
submitted by lsmarshall(417),
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An lraemteinexp sdgien or ernmteaelxip yutsd stmu veah an ironennvetti, yb i.otfendiin ao-tosclCnre dseisut aer lobventsoarai dtisseu, not rtl.eamniexep Tihs iuqnotse si chyeicltlan oir.crnect eThy dwenat ot meak a intpo hatt e-sltoacncor eidtssu rea mtei dan ctos ftefeinic eiscn yteh ton'd qieurre ilfowlgon nsipetat erov miet or nya reeossruc deebssi anirwgnhrggvei/eiet ftir.nmnoaoi esCa iseesr cldou tno ttes tish thephiyso.s

oAsl, eht indrogw csoiastade" itw na radseecni s"kri setaomhw delsaul ot lon-aeotcrcs istesud ynlo nihgav eht ibaylit to nidf dosd fo an ntiscooaassi neewetb prxesoue adn eoucm,to btu otn hasibselt aculsa aih.eltsnprio

bigjimbo  classic nbme +1  
poisonivy  totally agree, I dont understand why the right answer is Case control since that is not experimental +1  
howdywhat  am I subject to this kind of poor wording for the day of the exam? +  
ajss  I bieleve so +1  



 +5 
submitted by catch-22(79),
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I owud do a cotreptresive cthroo ehre. I on'dt nkhit thsi nutsqeoi si rtoecrc nad pirdosev too ttleli aonrofntmii to gte hte ortercc ws.rena "mieT "ifiectfen si the aoetnpr dorw eerh tub yteh syimlp 'didnt iosnecdr tath esovtercetirp ochotr wulod eb a betert egndsi eehr sa long sa the ebialarvs rea .deocd

sherry  I agree. I was hesitating between the two choices. I still think cohort study is better regarding the "risk". I hope this kind of questions wont pop out on the real thing. +2  
soph  I think key here was they were measuring risk though +  
yex  I also chose cohort, since it is comparing a given exposure. +  
raspberryslushy  I was also thinking retrospective cohort study - just as time efficient, can look at risk, and the Q stem said the cancer was common, and I think of case-control for rare conditions. It's like they forgot a cohort study could be retrospective. +1  
boostcap23  The classic example they always give for why not to do retrospective cohort is because patients who have whatever disease your testing for are more likely to remember all their risk factor exposures than a normal person that doesn't have any disease. Of course in this case I'm sure the people running the study would be the ones who figure out how much arsenic was in the water but this also would be very time consuming to figure out for each individual person in the study. Thus a case-control study where you look at a group of people with >50 arsenic exposure and a group <5 arsenic exposure and simply see who has cancer and who doesn't would be easier and take less time. +1  



 +3 
submitted by misterdoctor69(46),

I think something not mentioned yet is the fact that odds ratio can be used to estimate relative risk in RARE diseases as per the Rare Disease Assumption (where disease prevalence is <10%). Although the cancer in this question is described as "common," (common relative to other cancers), the cancer is still probably rare overall.




 +2 
submitted by cmun777(28),

I think the key on this question is recognizing how much "most time-efficient" jumps out in the question stem - a pretty unique thing to be specifically asking. Going off that and the fact they want to look at exposure -> outcome, by far the fastest approach would be to find people who currently have the dz in question and then just ask them if they have a previous exposure aka case-control.

an_improved_me  I feel like you just described a prospective cohort? Find ppl with the disease (same populatin and outcome), and then see if they had a similar risk factor; then follow them to see if they had a risk factor. Case-control would be: Have two groups of people, some with the Dx, others without. See if there is a difference in proportion that have/don't have a risk factor Someone please correct me if i'm wrong? +  



 +1 
submitted by al1234(1),

If it had stated a 'Rare Cancer' I would have thought case control. But it said common cancer.... Any thoughts on this?

kbizzitt  I believe what they are getting at with the "common cancer" is that it is easily definable as a case. This way you can easily determine who is a case and who would be a control. Then you go back and see if that case had exposure or not. +  



 +0 
submitted by soph(62),
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I ihknt key heer is hyet are natteivggisni hte sstpyheiho fo onatmmu fo iniecarsn taewr secseniar SKIR of .ncrca...e stbe way to sumreae rsik is scae tnool.cr

nbmehelp  If they were measuring risk shouldn't it be a cohort study though? By looking at first aid.. +3  
270onstep1  They both can determine risk. Key here is the time efficiency of case-control studies when compared to cohort. +  
suckitnbme  Case-control only determines odds ratio which is not calculating risk. In rare diseases the odds ratio can be used as an estimate of the risk ratio however. +1  



 +0 
submitted by dentist(56),
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ettrpy godo msmrauy

drdoom  welcome, O great physician of the skull and oral cavity. we revere your intricate understandings of the face, jaw, maxilla and all their tiny and hidden foramina. teach us your ways. +7