The trouble with Friedewald..

El_Dangeroso

Hi everyone,

Newbie to this forum so go easy on me!

I mostly frequent the nutrition and diet forum, I'm a complete nutrition nerd and my research extends to pretty much all aspects of health affected by nutrition.

One of the more common queries on the forum is 'Help! I have high cholesterol!'. Now obviously we cannot dispense medical advice, just dietary and exercise strategies that have sound scientific backing.

Two things I have noticed:

1. Some doctors seem to be concerned about high total cholesterol (not crazy high like with familial hypercholesterolemia) even though the breakdown is really good (high HDL, low trigs, good BMI etc.). Now as far as my own research goes total cholesterol is a terrible predicator of CVD risk unless you're talking about outliers and exceptionally high numbers. In fact in women the higher TC is associated with lower mortality. (Framingham study and others)

2. Some doctors seem to be generally unaware of the foibles of the Friedewald equations used to calculate LDL. Most know that the formula becomes inaccurate when trigs are very high, what seems lesser known is that it is also inaccurate when trigs are low, like <1.10 mmol/L. This leads to an artificially inflated LDL calculation. One lady in particular had calculated LDL of 4.6, but when adjusted for her low triglycerides the calculation was 3mmol/l. This could be the difference between prescribing a chol lowering medication or not.

So I guess my question is why is this not better known? What's the education surrounding cholesterol lab values and do you think it needs to be changed?

Thanks and all thoughts welcome!

2Scoops

Temple_Grandin wrote: »

2. Some doctors seem to be generally unaware of the foibles of the Friedewald equations used to calculate LDL. Most know that the formula becomes inaccurate when trigs are very high, what seems lesser known is that it is also inaccurate when trigs are low, like <1.10 mmol/L. This leads to an artificially inflated LDL calculation. One lady in particular had calculated LDL of 4.6, but when adjusted for her low triglycerides the calculation was 3mmol/l.

Modified Freidwald equation perhaps? Nothing to see here, IMO. Your problem is not with the equation but people's inability to recognize and work around its limitations. Friedwald's equation is elegant, inexpensive and correct more often than not. Alternate models and direct measurement of LDL-C are indicated where use of the eqn is not appropriate.

El_Dangeroso

2Scoops wrote: »

Modified Freidwald equation perhaps? Nothing to see here, IMO. Your problem is not with the equation but people's inability to recognize and work around its limitations. Friedwald's equation is elegant, inexpensive and correct more often than not. Alternate models and direct measurement of LDL-C are indicated where use of the eqn is not appropriate.

Oh no, absolutely. Sorry if I wasn't clear, I'm not saying there's a prob with the equation, I'm aware of the modified version. I'm just saying the modified version doesn't seem to be implemented for people with very low trigs. I've just come across a few people who, having implemented a healthy diet, are freaking out that their LDL went up and their doctor wants to put them on a statin, when more than likely just the triglycerides went down. Would that be the responsibility for the lab to calculate on the correct formula then? Are doctors educated about this possibility in med school? I just don't know how the usual procedure works.

As far as I know NMR and VAP tests don't seem to be that common in Ireland, although I presume that will change when the price comes down.

Tree

AFAIK to date there hasnt been sufficient cost-benefit shown in identifying subtypes of cholesterols, so VAP isnt likely to be coming in anytime soon, certainly not on a HSE large scale hospital measuring thingy.

lynnsback

VAP won't hit here anytime soon, even though eminent cardiologists recommend it as a very sensitive test. We are just so behind the times in this country. My local lab couldn't even test my Free T3 level for God's sake and have had to send it off elsewhere! Considering it is the active thyroid hormone and included in the basic panels of pretty much every other country; it is pretty mind boggling!

The Friedewald equation does have its limits yes. However, docs should be trained to recognise that low trigs skew the equation. They are not though, as the medical world is overrun with the 'statinators'.

El_Dangeroso

Tree wrote: »

AFAIK to date there hasnt been sufficient cost-benefit shown in identifying subtypes of cholesterols, so VAP isnt likely to be coming in anytime soon, certainly not on a HSE large scale hospital measuring thingy.

That's the trouble with implementing a utilitarian approach to medicine IMO. The majority may be well served by the normal test, but the few who have high LDL but with a high proportion of big fluffy particles are seen as being just as sick as someone with mostly small-dense or oxidised LDL.

Don't see there being any impediment to implementing the modified equation though.

Tree

implementing an equation mightnt be challenging, but the actual testing for VAP wouldnt be cheap. Doing VAP on a large scale wouldnt be economical or anyjmkore more useful than the current testing for the majority of samples. Refering on the occasional sample that might benefit a specific case is more reasonable, but should obviously be restricted to samples that would genuinely require it.

Unfortunately, costs and economics have to be taken into account in medicine as much as in anything else.

El_Dangeroso

Tree wrote: »

implementing an equation mightnt be challenging, but the actual testing for VAP wouldnt be cheap. Doing VAP on a large scale wouldnt be economical or anyjmkore more useful than the current testing for the majority of samples. Refering on the occasional sample that might benefit a specific case is more reasonable, but should obviously be restricted to samples that would genuinely require it.

Unfortunately, costs and economics have to be taken into account in medicine as much as in anything else.

Of course.. not holding my breath for VAP, not even sure it's advisible to have wide-scale VAP testing, even if it was cheap, just maybe in situations where people feel like the chol test is at odds with what they are doing in their life.

I've always felt wary of too much testing, I mean if you get a test done and it's good, you try and live healthy to maintain it. If the test result is bad then you try and live healthy to reverse it, either way the outcome's the same!

Slightly O/T, but found this study press release today:

http://newsroom.ucla.edu/portal/ucla/majority-of-hospitalized-heart-75668.aspx

Seems like LDL is a poor predicator in that study, maybe it should be ignored altogether in favour of some kind of HDL-trig ratio, that eschews the need for any fancy expensive tests too?