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NBME 24 Answers

nbme24/Block 1/Question#1 (79.2 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 neitpalexmer dniegs or meaenrltiexp utsdy must veha an retviiontenn, by .niotidienf es-lCnrcooat udtsise ear oalinoabsvter tessdui, tno lr.aieemnxtpe hisT tqeousni is ltenlchyaci rcconeir.t hyeT deawtn to kmea a ptoni ahtt tcale-osronc dseuits era meit dan tcos fitecienf incse hyet 'ndto iurerqe glowlfoin tasnipte vore miet or yan euoersrcs esibsed ierwngagertnegi/ivh .mitonofarni sCae rsseei dcuol ont etst hits hyt.hosespi

Asl,o het iowrgnd tasaeso"cdi wti an eaicredsn s"irk wtoamehs sdallue ot ctansero-ocl ssdtieu loyn ingavh hte lyatiib to nidf sodd fo an osoatnsiisac teweebn uoxeersp adn ocot,eum btu nto silsbehta alcusa apei.srthniol

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 duwo od a prsovrtteciee hrootc h.eer I ntd'o hintk siht eqisnuot si etrocrc dna veprsiod too iettll ftmrnioanio ot egt het rccrtoe wsne.ra Tme"i tein"ifcef si eth aroptne wdro ehre tbu tyeh mpilsy t'idnd nocrsdei ttha tereesvtproic rhooct ludow be a eettrb nsedgi rhee as olng sa teh laairevbs rea ded.co

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(61),
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I knthi yke hree is ythe era vgiiitsnaetgn teh ospsteyhhi fo tmaonum fo ercanniis ertaw nasrseeic SIKR fo c.r.n.ce.a tsbe ayw ot uraemse risk is caes notlc.or

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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rtetpy dgoo msayrum

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