Positive Predictive Value - The role of prevalence

In today’s session, we’ll explain what positive and negative predictive values are, why they are useful, and how the positive predictive value is influenced by disease prevalence.
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[@Banger11able]

Thank you very Much .. Very Helpful for my Epi/Stat exam scheduled after 1 week ...

[@sadiqal-herz7964]

Thank you

[@ummuhammad5543]

Thanks

[@heimonmipohlong7564]

How do you get 720 TN

[@islammohammadshehata1352]

Thanks sir, it can not be clearer !

[@abdulayodeji1450]

it literally can not be clearer

[@bipinsam4578]

You are very fast..Had to pause and rewind the video so many times to understand what are you trying to explain here...By the way , video was informative and helpful but next time please slow down a bit..Thanks !

[@givemestrength8416]

I understand that calculations I just can’t get my head around what it all means..It’s like say a test was 90% accurate how can we be sure if there is still none doubt who actually is positive and negative ie we would only know if it was 100% accurate

[@OriginalAndroidPhone]

This seems wrong (although I have confidence you are right, and I am wrong). In the pilot example, of course, prevalence will affect the usefulness of LBBB as a marker for the disease, but the specificity of the test would also be different in the private clinic vs acute cardiology ward.

[@bonob0123]

no he's right. Specificity is a characteristic of the test, not the population. It says if I take a 100 perfectly healthy controls and test them, what percent will be correctly classified as healthy by the test? Say that is 95%. In the private clinic versus cardiology ward there may be different number of people who truly have cardiomyopathy vs healthy but the test will still operate at 95% specificity; it will just be 95% of different numbers. The PPV takes this prevalence issue into account as explained in the video and so even with the same sensitivity/specificity the PPV will be different for the two different populations in the clinic versus ward.

[@LukeThomasPerth]

bonob0123 I understand what u mean but I don’t think you explained it very well. I suppose it is hard to explain

[@dr.shadmbbsdphmasco]

@@LukeThomasPerth nope he is right