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Skip to 0 minutes and 15 seconds The next session we’re going to go over is measures of Association and I call myself in a humorous fashion a drug information or a literature level enthusiast and I’m hoping that maybe by the end of these sessions you might be too. And this is actually one of my favorite sections because I think it has the most applicability to be able to make decisions that will affect patient care. The objectives are these we’re going to primarily focus on NNT & NNH which I think are the most applicable to making changes in patient care based on trials.

Skip to 0 minutes and 49 seconds So I’ll make sure that if a good understanding of the terminology around them how to calculate them and the components that are gonna need needed to explain them because the number by itself doesn’t really mean anything. So just some terminology I’ll just briefly go over these and you can refer back to them when you need to The main purpose of knowing the terminology is that if it’s listed in a trial you will be able to explain what that means irrespective of what it’s listed in the trial. So these measures of associations are mainly OR, RR and HR and or is the odds of something happening which is simple to remember because it’s called the odds ratio.

Skip to 1 minute and 28 seconds The relative risk or risk ratio is the probability or incidence of event occurring and is listed either way as RR. and another one is HR which is very similar to RR and this is usually related to a negative effect and based on time. And the important factor that we’re going to go over and continue to discuss is the number four on this that none of these take and we’ll talk about RR in a second, none of these take baseline risk into account which can be difficult than to extrapolate these to patient care because the number can be arbitrary and I’ll give you some examples of that.

Skip to 2 minutes and 5 seconds So I mentioned just relative risk reduction it’s estimated at baseline the risk that is removed. And we’ll see it’s just 1 minus RR. And the absolute risk reduction and the NNT and the NNH as you can see in number 8 they do take baseline risk into account., So that way if a patient is sicker or healthier this one will provide more accurate information as to what you will see. The absolute risk reduction gives you the difference in the event rates and it’s usually listed as number of patients who are spared an event NNT and NNH depending on what you’re looking at something good or bad prevent benefit or harm in one additional patient.

Skip to 2 minutes and 43 seconds So just a little side-by-side comparison is to clarify these before we we move on to discuss some more specifics. The risk ratio which is RR is the risk an event in treatment divided by risk in control Then the RRR is the percent of reduction or removed of the event and then ARR is the actual difference in the event rates and this as I said listed his number of atients spared the event and then the NNT and NNH is number of patients needed to prevent benefits or harm one additional patient depending on what you’re looking at and I’ll provide plenty of examples that these will make sense.

Skip to 3 minutes and 22 seconds But first I want to make sure we understand why baseline risk matters and why we’re going to focus more and in ARR, NNT, and NNH when unfortunately most studies will provide you with either RR or RRR which is often difficult to extrapolate. So you can see that the RR and RRR as I’ve mentioned do not take baseline risk or severity of illness into account. So this can falsely elevate the potential improvement that is seen in a clinical trial.

Objectives for this Lesson and MOA Terms

Prof. Mary Ferrill illustrates the objectives for this lesson, including interpretation of NNT (Number needed to treat) and NNH (Number needed to harm).

The purpose of this week is to make sure that we are able to define, calculate, interpret, and describe NNT/NNH in clinical trials, determine when it is appropriate to calculate NNT/NNH, and develop an NNT/NNH statement utilizing the required six components.

Besides, we also need to know the eight kinds of definitions of MOA terms. The main purpose of knowing the terminology is to be able to explain what that means irrespective of what it is listed in the trial.

The absolute risk reduction (ARR) and the NNT/NNH take baseline risk into account. If a patient is sicker or healthier, they will provide more accurate information.

As for side by side comparisons, we have to understand the definitions of RR (Risk Ratio), RRR (Relative risk reduction), ARR, and NNT/NNH.

Why baseline risk matters? Please watch the video and share your thoughts below.

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This video is from the free online course:

Evidence-Based Medicine in Clinical Pharmacy Practice

Taipei Medical University