AHI 4% calculation?

jnk... wrote: ↑

Tue Sep 18, 2018 2:00 pm

Arlene1963 wrote: ↑

Tue Sep 18, 2018 12:03 pm

I came across this a while back and am still surprised by how utterly "unregulated" this field still is in some respects.
It would be like saying that you have different ways of determining if someone has hypertension. > 140/90 or >130/85, for example. Doctor gets to choose. Would any of us consider this good medicine?

Yet, in the world of sleep medicine this is how it has worked since around 2012 when the AASM rules for scoring for hypopneas changed.

https://aasm.org/aasm-clarifies-hypopne ... -criteria/

Two definitions can be used for scoring an hypopnea, and depending on which one is used you can be diagnosed with no OSA or moderate to severe OSA depending on the lab's scoring practices.

I read one example here about a year ago of someone who had an AHI of less than 5 when their PSG was scored using the 4% desat for hypopneas as per Medicare rules, and yet when scored under the 3% criteria this person's AHI was moderate at 18 events per hour. So, who decides if this person gets an XPAP prescription or not?

Go figure. It really is crazy.

Something is just not right. This needs much more scrutiny.

I get where you are coming from. But the issue is the insurance industry more so than anything else, I think. The sleep industry has already chosen, but not all the payers will go along. So it isn't really the doctor who chooses; the person's insurance has already made the decision for him.

Most medical testing is less precise and definitive that we'd like to think, anyway. There is a gray area between "at this result the person's treatment will be paid for" and "at this point the person SHOULD be treated." That gray area is valuable for giving patients and docs some wiggle room for exceptions and common sense, as customized to other factors. The problem is when we as patients insist on being treated when we've crossed the line into CAN be treated but way before SHOULD be treated, even when the treatment may not be best for us. Of course, the other issue is the docs who insist on treating everyone the same, as well. There is nothing magic about the 5 AHI line other than it being the line in the sand at which insurance agrees to let someone try PAP. That doesn't mean medically that someone with a 4 AHI wouldn't benefit from treatment OR that everyone with a 6 AHI should be put on CPAP.

The AASM recommendation has it right. Insurance needs to cave on this. In my opinion. And I've got a bunch of 'em.

This is a very valid point!

All this discussion made me go back to my own sleep report b/c I vaguely remember what was in it as it was just completed this June and I started CPAP treatment in July. Aside from what my AHI I didn't really care too much about anything else other than my apneas were obstructive and my AHI was above the insurance limit of 5 AHIs. I go wondering and dug up my sleep report and it turns out the clinic that did my sleep study used the 4% AHI calculation formula! It states that using the 4% AHI calculation method that I had a combined AHI of just 5.9 but then it went on to say that when I sleep on my side I had an AHI of 3.0 and in supine it was 8.0. That being said my AHI in the report is technically "conservative". I do very vaguely remember the sleep clinic that did my study say that my AHI was technically higher, as much as 10ish or so but I don't recall what the reasons or circumstances as to how he came up with that number. Probably RAW AHI not using the 4% method. I guess I'll never know since I don't deal with the clinic that did my study.

I guess I lucked out given that my AHI 4% calc method still scored me having an AHI above 5 which qualified me to start CPAP treatment and get my equipment paid for by my work insurance. Had I not been put on treatment (I was given the option to not treat it but I figured I had NOTHING to lose by using CPAP) I would likely still still be suffering from moodiness and mental fog. I seriously thought I was ADD (I probably am) but with CPAP therapy I have much better focus on things I'm working on. I feel for those that probably suffer from any form of apnea that are denied CPAP just b/c of an AHI number and testing method that some folks in a room decided on. CPAP given how inexpensive the components are inside the units should be made more readily available to the public.

I agree with you Steve and this is why I think that folks need to be told that there are different ways of scoring hypopneas in diagnostic PSGs.

MANY folks when told they have an AHI of 5.9 would think "nah, I have borderline mild OSA" and wait for another 10 years until it develops into something more serious before considering using XPAP, packing on weight and adding health issues along the way. Especially when given the option of NOT using XPAP by their sleep specialist.

A well known and highly respected poster here called Robysue had an AHI of less than 5 using the conservative 4% criteria and yet her AHI was calculated in the 20s using the alternative recommended AASM criteria for hypopnea and arousals.

It's worrying that a disorder with such serious consequences is subject to wide swings in interpretation and in determining who gets treated.

I'm pretty sure that in Ontario a person with a diagnostic AHI of 5.9 would not get a prescription for XPAP. I understand that this is financially driven, but at least let patients know that there are two ways of scoring hypopneas, and give us the option of self treating. This is my biggest beef with the current system.

The other issue is mandatory OSA testing for certain occupations.
Which definition is used for scoring hypopnea and is it consistently applied? Let's hope so.

For AHI below 20 or so, it is the reported symptom of sleepiness, as assessed by questionnaire, that carries more weight for diagnosis than the specific AHI number anyway.

The AASM is consistent in its recommendation. It is the payers who are inconsistent in accepting the AASM recommendation. As I see it. AASM allows a lab to keep its accreditation using an alternative definition, because otherwise payers would abandon labs completely and only use home testing. Which brings up that issue--for many patients, PSG-hypopnea definition doesn't even matter because they aren't getting a PSG to support the diagnosis anyway.

There are other conservative/liberal considerations in interpreting PSGs that have more impact on consistency than the specific hypopnea definitions used. Software scoring and human scoring varies from lab to lab and from one sleep doc to another. Medical testing is inexact for most conditions.

In many respects, moderate-to-severe OSA as assessed by AHI is considered a completely different beast from mild-to-moderate. As a general rule, moderate-to-severe-range AHI should always be treated, whether a person is reporting sleepiness or not, but mild-to-moderate without reported sleepiness is always a gray area. Using PAP therapy on the mild for prophylactic purposes, to prevent progression of sleep-breathing problems, in not an accepted concept in the mainstream--you treat present condition. I do believe in pressuring (oops, I mean, educating) a patient with moderate-to-severe-AHI range to get them to try PAP but not pressuring one with mild-to-moderate-range AHI and no reported sleepiness or sleep-related symptoms. In fact, a person with no sleepiness reported would be unlikely to have a reason to even be tested. There has to be a significant indication of a need to test quality of sleep for it to be tested at all, since there is no wholesale screening for it.

In other words, addressing the 5 AHI line in the sand is a discussion about payers, whereas the 15/20 AHI line in the sand is about treatment decisions, from my point of view. Bottom line for me is as long as the overall system is for payers to call the shots, many people who might benefit from PAP will never get the chance to find out, and that's a shame in that it is caused by keeping the machines from being OTC.

My views are my own, and may be further in left field than I know.

I was very fortunate that where I live that as long as as my AHI is over 5 (whether it is using the AHI 4% calc or not) that I was able to get a prescription from a doctor to treat it. With the insurance companies here all they wanted was a prescription from a doctor and nothing more. Some insurance companies want a trial done and sometimes they want to see compliance data for xxx period of time but otherwise it is fairly straightforward to get a unit. Given my low AHI numbers I even told the doctor that I could go without as I wasn't overly interested in strapping on all this stuff to my face in hopes that it would help me sleep. I was asked a questionnaire prior to my sleep test on things like tiredness, attentiveness and irritability as well as host of other Q's that clearly indicated to the sleep doc that something was amiss with me. This was why my sleep report stated 4 possible solutions:

1. Use CPAP therapy
2. Lose weight/stop smoking/stop alcohol (I'm a bit overweight but I don't smoke and I'm hardly consume any booze).
3. Sleep on my side (not really possible for me b/c of a bad shoulder).
4. Surgery to correct my throat (basically tonsil removal).

Thank goodness my doctor is very understanding. When I did my follow up she wasn't interested in my sleep AHIs but asked how I felt and she was happy to hear that I'm not the moody b*tch that I normally am.

Shame that others that don't quite fit the criteria for textbook apnea may be denied treatment. Knowledge is power and for think more awareness needs to be put into place to educate those that would otherwise be clueless on a possible OSA condition.

As the textbooks are slowly being updated, insurers continue to drag their feet.
We are already aware that using cpap needs to be voluntary.
Now it appears that some apneacs might need to be aggressive.
Not easy when you are beat down nightly by apnea.