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NBME 21 Answers

nbme21/Block 3/Question#21 (48.4 difficulty score)
A screening program is instituted for ...

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submitted by drdoom(819),
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5,020 nsuttdes ... btu oyu ifdn otu ignrud uory aitnili ecsnre ttah 050 aelydra heva eht a.sdiese oS, ttkouires tseoh .opepel tTha laeesv 002,0 susdettn who t’don evha teh essdeia.

vOer eht rusoce of 1 a,yre yuo civsoedr 200 tsdnuset oledepvde hte oinnif.cte us:Th

200 wne sasec / 00,20 epploe woh id’tnd evah the dsiasee henw ouy edsratt ouyr ytusd = 10 crnepte

Tkciyr, iyrkct BMEN ...

sympathetikey  Ah, I see. Thank you! +  
niboonsh  Im mad at how simple this question actually is +7  
sahusema  Incidence is measured from those AT RISK. People with the disease are not considered to be at risk. So 2500 - 500 = 2000 people at-risk. Of those 2000, within one year 200 develop the disease. So 200/2000 of the at-risk population develop the disease. 20/2000 = 10% = incidence +3  
daddyusmle  fuck im retarded +2  

submitted by drdoom(819),
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’nDto tfgeor ahtt idcncneei si eht munber fo wne sscae hiwch emegre ni na eueaftncdf tnoplaoupi. inIecdcne is ngrity to egt at eth uitnsqoe ;g&t- n“I a ingev ye,ra owh amny ewn polepe lopeved shti ai?sed”es

nI hrtoe so,wdr you ntocna utocn eopelp who rdeaayl hvae eht edissae. Yuo ehva ot cxeeudl ohets pepole ofmr ouyr aluocat.licn ouY tawn ot oknw, oangm lal eht eplepo tou ereth owh DO NOT eahv hte ease,sid woh many emtis siht raey was eeonoms e)n(ywl noid?esdga

daSi tyelnrfefid itl,sl uoy ntdo’ tnaw ot n-“to”oucdulbe lppeoe hwo loeeedvpd hte essedia rbefoe your dystu. As na ligpims,idoeeto thta dolwu cwers pu oryu neses of ohw fevenitic ro bmielsstnsira a adsiees si. Yuo ntaw ot nw,ko m“for teim1 ot teim2 how amyn new cssea rm”degee?

questioneverything  You would count the total risk pool. Chlamydia is not a chronic disease so you would treat those 500 people and they would return to the risk pool. +  
drdoom  But you would first have to determine that they CLEARED the infection. What if you gave them tx and then they come back and say, "doc i got the chlamydia" -- is this a new case or did the tx fail? You're assuming it cleared but maybe it didn't. That's why you want to EXCLUDE from the start anyone who might already have disease of interest. +7  

submitted by questioneverything(3),
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kO I egt ahtt fi 500 edaalyr eavh eth dieseas etnh the irks oolp is pdorped to 0020 tedsunst btu teh ioenuqst pciylcislfea yssa that eth stte si deno a eyra le...irfat 500 lepepo adh lydmcaiah, oyu odlwu retta tmh.e ouY td'no bemcoe mineum ot miclhadya rfeat ftoeninic os yteh odwul go cakb onti eht ksri lo,po ineamgn hte oplo ulowd urtenr to .0052 Teh snwear husodl eb ,%8 sith saw a dab eq.untiso

thepacksurvives  Yeah, this was my issue. I got it wrong because of this-- still don't understand the logic bc you can get chlamydia multiple times +5  
hungrybox  FUCK you're right. Damn I didn't even think about that. That's fucking dumb. I guess this is why nobody gets perfect scores on this exam lol. Once you get smart enough, the errors in the questions start tripping you up. Lucky for me I'm lightyears behind that stage lmao +8  
usmile1  to make it even more poorly written, it says they are doing a screening program for FIRST YEAR women college students. So one year later, are they following this same group of students, or would they be screening the incoming first years? +5  
dashou19  I think the same at first, but after a second read, the question stem said "additional" 200 students, which means the first 500 students don't count. +  
santal  @hungrybox You are me. +1  
neovanilla  @usmile1 I was thinking the exact same thing... +1  
happyhib_  I agree this is a trash question; I was like well if this is done yearly for new freshman the following year would be of the new class (but the word additional made me go against this). Also you could assume that they were treated and no longer have the disease... I dont like it honestly but know for incidence they want you to not include those with disease so i just went with dogma questions on incidence to get to 10% +  

submitted by drdoom(819),
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oAsl esniodrc hsti gerat csiedpiront omfr eht IHNs’ eMHS aatbaesd:

NCICEDINE: hTe rubnem fo ewn csaes fo a envig aisesed guindr a ivgen epoidr ni a dfieciesp l.uiponpota It oals si used fro het etar at hhwic new estnve ucroc in a edndfie ioaptnu.plo It si ftiieeeadtfdnr morf AEPEVNCLRE, whhic eefsrr to lal scsa,e wen or odl, ni teh inuootplap ta a gniev emti.

questioneverything  The prevalence of chlamydia in this group would be 0. It is not a chronic disease. +  

submitted by usmle11a(73),
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eht oeunisqt tseond yas atth teh 005 tgo ur,ecd so ti wlli be 2000 ohw era ta s.rik