How to Calculate Positive (PPV) and Negative Predictive Values (NPV)

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This is not medical advice. The content is intended as educational content for health care professionals and students. If you are a patient, seek care of a health care professional. Kai thoroughly explains the process of how to calculate positive predictive values (PPV) and negative predictive values (NPV) in medical statistics.
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[@catr14]

Hiii! I am a physical therapist and recently took the NPTE here in the US, and Thank God I passed!!! I really would like to thank you for sharing these easy-to-learn videos (especially thr special tests!!!) to all of us. You have been such a blessing. Thank you!!❤

[@Physiotutors]

Congratulations - very happy to hear that we could help you with passing!

[@rollandjonathan8085]

Well put altogether. Finally I understand how to calculate the Predicitve Values (PPV &NPV). Really appreciated.

[@matthewthaddeus6673]

you all probably dont give a damn but does anyone know a trick to get back into an instagram account? I stupidly lost my login password. I would appreciate any tips you can give me

[@valerietalbertvt]

Thank you so much, I didn't understand in class because the teacher didn't know herself. please keep posting .

[@Physiotutors]

We certainly will Valerie!

[@Nwihsphysio]

Very helpful Sir, please explain Validity and Relability .

[@muhammadsaleh6665]

Great piece of work. You teach us so well. Appreciated!

[@Physiotutors]

thanks for the compliment!

[@sengiyumvakandusi19]

Thank you so much, very helpful Information

[@Physiotutors]

You're very welcome!

[@rutvishah9596]

I have a question. You said PPV is all the people who have the disease upon people who tested positive. Then shouldn't it be TP+FN(because they also hv the disease)/ TP+FP?

[@Maurice_LLB]

Hi, @ 1.31, 650 + 250 is 900 right. Is it a small mistake? It was 750 + 250 = 1000 right?

[@sarahreid7599]

Thank you so much!!! You made this easy. Thank you for your help, S

[@Physiotutors]

You're welcome! thanks for leaving a comment 🙂

[@Wen-tz8lh]

Thank you. But i am confused. Are the Sn and Sp often used during clinical trials in order to determine the Sp and Sn values. Thus, allowing us to choose the most accurate Sn and Sp tests to the patients?

[@ivancarlson953]

in other words, one can also use the Bayes' Rule formula PPV = (0.25 x 0.88) / [(0.25 x 0.88) + (0.75 x 0.10)] = 0.7458 or 75% NPV = (0.75 x 0.90) / [(0.75 x 0.90) + (0.25 x 0.12)] = 0.9574 or 96%

[@akanjiolakunle4999]

Great video, clear explanation!

[@allearner366]

Thank you for your work, but I am confused. We came to this video because, in the sensitivity and specificity video, you mentioned usually we do not have the information in the table and this is right because we do not know who FN and FP, but here you still use the same table but in different equations and test type. The problem that PPV and NPV are supposed to solve is that we do not have the information on FP and FN. I do not understand what is the point of these tests.

[@Physiotutors]

The problem with Sn and SP is that they determine how many of the patients who have tested positive or negative on the gold standard will have a positive or negative outcome on our index test. It's the other way round than what you want to do in practice. In practice you have a patient and you would like to know how much more likely/less likely the chance for a disease is after they test positive/negative on your index test.

[@mireyajones810]

@@Physiotutors Thanks for an ABSOLUTELY worthless bunch of drivel. No sick person cares if they test positive or negative on a worthless diagnostic. Typically, the "diseases of modernity" are functions of mineral and vitamin deficiencies. There are no TESTS for D3 or magnesium levels. Rather, we can measure one's level and speculate if changing said level will alleviate illness or provide cure. One good example is the relationship between respiratory illness and selenium levels. See Ge and Yang (1993), American Journal of Clinical Nutritional Supplementation, 1993; 57: 259S-63S. (Why should I know more than you guys ... it is as if you never do any research and cannot think).

[@mireyajones810]

AI Learner - YES!!! You are correct. The concept of PPV is a meaningless tautology, whereby the allopaths declare that you should or should not be sick, based on their diagnostic tool - regardless of the validity of their instrument. See my response (below) to their worthless reply to you.

[@dr.monikabhuriya10]

Thank you sir.

[@user-yt7hc4wt2g]

Awesome .. Thank you for sharing these videos

[@Physiotutors]

No worries, you're welcome!

[@sarahmartee]

thanks, holy crap, i hate statistics, but this explanation made sense...

[@Physiotutors]

Happy to hear Sarah!

[@sailiscriviner5411]

Well explained.

[@LuciusDragonwolf]

How to calculate pro wrestling workrate if I incorporate statistics and formula ???

[@zuluzero4659]

A question in my exam is asking: If a test was 99.9% specific how many test results out of 1000 would be faulse negatives? Can you help me with this please??

[@Physiotutors]

Have a look at our video where we calculate sens and specs in a 2x2 table. There you can see that the false negative rate does not affect specificity. So the correct answer would be: we don't know.

[@zuluzero4659]

@@Physiotutors thank you! I will discuss this with my tutor! Xx

[@charlesthehandsomeandbrave2956]

I like that content cop opening

[@alessandrociari3112]

you're the man!

[@Physiotutors]

Thanks!

[@user-gr2vi6du9y]

Where did you get 1000

[@anthonymclees9830]

papa bless

[@arvindkumargkumar7535]

If negative 👉 it's only situation not results Results can be converted to positive 🙏

[@liwangaliwanga3466]

📌

[@rishabcreator]

I didn't get it😔

[@MM12331]

675 plus 75 is not 650 my friend.

[@mireyajones810]

I cannot see how this concept (PPV) avoids tautology. In the case of AIDS, the definition of the "disease" is: (a) HIV + antibody test; + (b) one of about 30 types of illness (pneumonia, flu, anemia, etc.). To declare that someone has a disease (e.g., SCURVY) and then tests positive for "the disease" or tests negative is nonsensical. If on the other hand, one believes that BRCA genes are the "cause" of breast cancer, and a person has a tumor in the breast tissue, yet tests negative for BRCA 1 or 2, do we declare that the "test" failed? A better explanation is that the "test" for the disease is invalid.

[@Physiotutors]

The problem in your example is that the antibody test is part of the gold standard. Not sure we get the rest of your examples.

[@hasanalomar9632]

uke ist schiesse

[@Kevin-yt9vi]

Thank you very much

[@Physiotutors]

Ur welcome Keisha!