More about likelihood ratios in diagnostic testing:

Jaeschke R, et al, JAMA, 1994.
www.pubmed.gov/8309035

Interpretation for both LR+ and ILR- in terms of how conclusive the test changes pretest to posttest likelihood of a positive (or negative) finding:

>10 = large
5-10 = moderate
2-5 = small but sometimes important
<2 = inconclusive

Inverse negative likelihood ratio (ILR-) = 1/LR- = specificity / (1-sensitivity) = 92.3% / (1-41.2%) = 1.6 = how many more times likely it is that you do NOT have the disease in question thanks to the test

Positive likelihood ratio (LR+) = sensitivity / (1-specificity) = 41.2% / (1-92.3%) = 5.4 = how many more times likely it is that you have the disease in question thanks to the test

However, sens and spec values are highly dependent on disease prevalence in the population being studied. The measures of test performance that are independent of population disease prevalence are likelihood ratios, which tell us how many times more likely a diagnosis is after applying a test.

In Apple’s white paper on their Hypertension Notification Feature for Apple Watch, they report low sensitivity (41.2%) and high specificity (92.3%). They rightfully chose a threshold for notification while seeking to keep the false positive rate low.

The white paper: www.apple.com/health/pdf/H...

Read on if you are interested in (the Apple Watch) diagnostic test performance.

It's all about the likelihood ratios.

I still applaud Apple and think the Hypertension Notification feature will be useful for the individual and society. Any nudge that can help early identification of hypertension is valuable, especially when it is passively integrated into everyday use of a consumer device as implemented by Apple.

In other words, you should NOT rest on your laurels and assume that you don't have hypertension. Get your blood pressure tested regularly regardless, because hypertension is very common, deadly in the long term, and highly treatable.

If you do NOT get a Hypertension Notification despite using your watch, then you are NO MORE LIKELY to be free of hypertension than before you used your watch (inverse negative likelihood ratio 1.6, which is inconclusive).

Very much so, in a way that has surprised me. We are currently studying this prospectively.

Not at all. I rather like the approach, which can be done without compromising scientific rigor, as in the following paper from our group.

PubMed.gov/39846063

In our experience, "accelerated aging" measured in years of healthy human aging is a unit of measurement that has unsurpassed clarity of understanding among the general public (patients). We need to be more 'tabloid' to get our message across, imho.

#CardioSky #WhyCMR #EchoFirst

We don’t yet have definitive data on it, but the non-LAVI (c) formula is likely best for short-term changes in PAWP, whereas (b) is just as good in stable hemodynamics, and (a) is good enough if you haven’t acquired PV velocities.

We have actually have three formulas for estimating PAWP.
From Lindow 2024 using:
a) E + LAVI
b) E + PVs + LAVI
and from Lindow 2025 using
c) E + PVs + PVd
Their accuracy, precision and prognostic association are presented in each paper.

Both HFpEF and HFrEF were included. However, it was limited to those with at most mild mitral regurgitation or stenosis, and sinus rhythm.

More details are in the paper.

academic.oup.com/ehjimp/artic...