USMLE Biostats 5: Sensitivity and Specificity, NPV and PPV and More! скачать в хорошем качестве

USMLE Biostats 5: Sensitivity and Specificity, NPV and PPV and More!

Want to support the channel? Be a patron at:   / lymed   Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day. Follow along with First Aid, or with my notes which can be found here: https://www.dropbox.com/sh/an1j9swvjx... Continuing our talk on biostats! We'll begin with some terminology. Let's imagine we have a test to look for HIV. If a patient has HIV and the test is positive, that's a true positive. If the patient doesn't have HIV and the test is negative, that's a true negative. If the test is positive, but the patient does not has the disease, that's a false positive. Lastly, if the test is negative but the patient does have the disease, that's a false negative. Now let's discuss positive predictive value (PPV) and negative predictive value (NPV). Positive predictive value is the probability that subjects with a positive screening test truly have the disease. Negative predictive value is the probability that subjects with a negative screening test truly don't have the disease. Next up, let's talk sensitivity. Sensitivity refers to the test's ability to correctly detect patients who do have the condition. In a sensitive test, if it is negative, it rules out the disease. This is related to negative predictive value. When we discuss sensitivity, the worse case scenario includes a false negative. The more sensitive a test, the less false negatives. Now let's discuss specificity. This is the bbility for a test to detect a particular disease. If it is positive, it's likely the patient has that particular disease. This is related to positive predictive value. The worse case scenario occurs when there are false positives and that has to factored in. The last part of this video will discuss a common graph they use to synthesize all of these factors. Our last topic will be on incidence and prevalence. Incidence looks at how many new cases there are in a population. Prevalence is the number of TOTAL cases in a population. Prevalence can change PPV and NPV. Know that incidence and prevalence are related to each other by time. In chronic cases, prevelance is often higher. In acute diseases, prevalence and incidence are often the same.