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xMenace

The Friedwald Equation

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xMenace

I think this is something everybody should have a rudimentary understanding of. Basically when you have your lipid panels done, your LDL is not measured directly. It is calculated. The equation is.

 

(if using US mg/dl) LDL = Total - HDL - Tri/5

(metric mmol/l) LDL = Total - HDL - Tri/2.2

 

Friedwald equation - General Practice Notebook

 

The Friedewald Equation

 

the ultracentrifugal measurement of LDL is time consuming and expensive and requires specialist equipment. For this reason, LDL-cholesterol is most commonly estimated from quantitative measurements of total and HDL-cholesterol and plasma triglycerides (TG) using the empirical relationship of Friedewald et al.(1972).

[LDL-chol] = [Total chol] - [HDL-chol] - ([TG]/2.2) where all concentrations are given in mmol/L (note that if calculated using all concentrations in mg/dL then the equation is [LDL-chol] = [Total chol] - [HDL-chol] - ([TG]/5))

the quotient ([TG]/5) is used as an estimate of VLDL-cholesterol concentration. It assumes, first, that virtually all of the plasma TG is carried on VLDL, and second, that the TG:cholesterol ratio of VLDL is constant at about 5:1 (Friedewald et al. 1972). Neither assumption is strictly true.

Limitations of the Friedewald equation

The Friedewald equation should not be used under the following circumstances:

when chylomicrons are present

when plasma triglyceride concentration exceeds 400 mg/dL (4.52 mmol/L)

in patients with dysbetalipoproteinemia (type III hyperlipoproteinemia

 

 

Note that there are limitations. For example it is not supposed to be used when triglyceride concentrations exceed 400 mg/dl (4.52mmol/L).

 

It should raise a red flag that our LDLs are basically estimated, and if you read about this equation, it is not considered exact. It makes me uneasy that my docs want to prescribe pills for an estimated risk.

 

Lipid Testing Inaccuracies

How do calculated LDL values compare to Betaquantification values?

 

The limitations of the Friedwald Equation for the estimation of LDL cholesterol are well known and well documented. Although many of us generally perceive the Friedwald equation to under estimate the LDL-Cholesterol, Warnick et. al. found that in some cases the Friedwald equation actually over estimated the LDL Cholesterol as evidenced by the plus or minus 10% comparison of the calculated LDL when compared to Beta Quantification. The overestimation results from the inherent imprecision of the Total Cholesterol, Triglyceride and HDL measurements. Since the calculated LDL is derived from these three measurements the imprecision of LDL measurement is the total of the imprecision of the three measurements.

I have also found suggestions that it even less accurate for very low triglyceride concentrations, but I have found little real evidence. One issue I face and I'm sure many others have is that our LDLs have risen with low-carbing. My endo of course wants me back on statins because of this, even though every other indicator of mine is fantabulous. The following article suggests that with very low trigs, these high LDL numbers are in fact quite overstated, but I can't find definitive proof except for the below Iranian Study.

 

Brio HealthClub

 

 

For years now and through many studies of various dietary interventions there was this weird phenomenon that a low carb diet would greatly improve all the blood lipids except LDL, which would stay the same or go up. The nay-sayers quickly pointed to the high fat dietary regime and said "SEE! It is bad for your heart. It makes your LDL go up!"

 

Here's the problem with that. It is now known that when Triglyceride levels are below 100*, the Friedwald equation also fails, significantly overestimating LDL numbers. Essentially the Friedwald equation punishes you for having low triglycerides, which is supposed to be a good and desirable blood quality to have. So if your doctor ever raises an eyebrow at your for an increased LDL level when your triglyceride levels are low, politely ask to have the LDL measured directly

 

There is one study called "The Iranian Study" which showed that a different equation works better for people with high cholesterol and low triglycerides.

 

The impact of low serum triglyceride on LDL-choles... [Arch Iran Med. 2008] - PubMed result

 

Statistical analysis showed that when triglyceride is <100 mg/dL, calculated low- density lipoprotein cholesterol is significantly overestimated (average :12.17 mg/dL or 0.31 mmol/L), where as when triglyceride is between 150 and 300 mg/dL no significant difference between calculated and measured low-density lipoprotein cholesterol is observed. In patients with low serum triglyceride and undesirably high total cholesterol levels, Friedewald equation may overestimate low-density lipoprotein cholesterol concentration and it should be either directly assayed or be calculated by a modified Friedewald equation. Using linear regression modeling, we propose a modified equation.

 

Someone even kindly built a calculator here LDL Cholesterol Calculator which does both versions.

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Subby

One of your quotes mentions getting it measured directly... have you asked your doctor John? Wonder how accessible that is, with a little pushing. Strikes me that the best option would be to dispense with the guesses full stop.

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foxl

I asked mine and was told, "We don't have to," unless Trigs are > 400.

 

WTH ... we are more concerned with my low HDL for now (which is why I am on the max dose of simvastatin, riiiiight?).

 

My secret plan is to lower the statins and increase the niacin, eventually ... if necessary.

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Rekarb

Once again, I just read the paper but don't know if I can find it but it stated that if trigs < 70 then LDL particle size is large and of no real concern.

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fgummett
Once again, I just read the paper but don't know if I can find it but it stated that if trigs < 70 then LDL particle size is large and of no real concern.
Beyond Routine Cholesterol Testing: The Role of LDL Particle Size Assessment... by Paul E. Lemanski, MD, MS, director of the Center for Preventive Medicine and Cardiovascular Health, Prime Care Physicians, P.C., and assistant clinical professor of medicine at Albany Medical College.
The LDL value reported to clinicians is the summed contribution in mg of LDL particles in a deciliter of plasma. LDL particles are, however, heterogeneous in size, density, and composition. A growing body of evidence suggests that LDL particles that are small and dense are more atherogenic than those which are large and “fluffy.” Thus, two patients with the same LDL measurement in mg/dl may have differing levels of cardiovascular risk depending on the relative proportions of small, dense and large, fluffy particles.
In other words: the reported LDL is a measure of "volume"... larger particles take up more volume so you may get a higher reading while having a lower risk.
Observational and epidemiological studies suggest those having a predominance of small, dense particles may have an increase in risk up to 300 percent greater than those having a predominance of large and fluffy LDL particles.
Individuals with TG below 70 do not have small, dense LDL.
also... http://www.diabetesforums.com/forum/other-medications/44265-small-ldl-its-clinical.html#post506969

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jps

At my lab, we estimate LDL and it's not valid if TG's are above 400.

 

However, we do also have measured LDL available. But a doctor has to put in a separate order for it.

 

For a comprehensive lipid profile, those that differentiate between particle sizes, you need to order the VAP profile. At this moment, there is only one laboratory/company (Atherotech) that offers this and it's located in Alabama, I believe. However, it's easily ordered by any physician. Just a simple send out, results within a couple of weeks.

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fgummett

I strong-armed my Doctor into ordering an Apo-B test... the lab were not happy saying it was "experimental", but I got a result anyway. The more folks doing this test, the less statins they will be able to justify/sell My result (November 2008) was 0.65 with a recommended value of < 0.9g/l

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foxl
This guy, Dr. William Davis, gets right to the heart of the matter. The Heart Scan Blog: Small LDL: Perfect index of carbohydrate intake

 

Intriguing .... "WHEAT being the worst" ... probably the main component I have dropped from my diet!

 

Not sure how much statin is supposed to drop my LDL, but it is half what it was 6 mos before diagnosis and I was on 2000 mg niacin per day then!

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sumi

I missed this thread! My cholesterol panel is back and looking pretty good without statins. Total Chol. = 5.21 or 201 (range 2.00 to 5.19) HDL 2.03 or 80 (range >1.10) LDL=2.84 or 112 (range 1.50-3.39) Triglycerides .75 or 67 (range .45-2.29) CHOL:LDL RATIO =2.57 (range <4.4 for high risk individuals). My question is, can your HDL be too high? I assume that it is added in to total cholesterol. My doctor, as usual would want me on statins to lower that LDL to under 2.0. but does my high level of HDL compensate? my ratio looks great to me.

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jps

As far as I know, the higher the HDL, the better.

 

It was once explained to me this way: LDL carries cholesterol AWAY from the liver, delivering it to cells and tissues that need it. Cholesterol is sticky. When the LDL carries the cholesterol throughout the body, some of the cholesterol will stick to the walls of the vessels. This now sticky vessel will entrap other particles such as white blood cells and cause the formation of a hard plaque on the arteries.

 

The role of HDL is as a scavenger. It runs throughout the body and picks up excess cholesterol and transports it back to the liver.

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fgummett
Cholesterol is sticky. When the LDL carries the cholesterol throughout the body, some of the cholesterol will stick to the walls of the vessels. This now sticky vessel will entrap other particles such as white blood cells and cause the formation of a hard plaque on the arteries.
Sounds to me like a great way to sell statins... :Dthe evil cholesterol is clogging up our arteries! :eek:

 

Imagine you are biking or running, fall and skin your knee... the body responds with blood, redness/swelling, serous fluids etc... inflammation in other words... but within a short time a scab has formed over the broken skin so that the process of healing can get under way. If someone with medical knowledge looks at your knee and says "you know, you could avoid unsightly scabs like that if you only took this drug which lowers your blood platelets, fibrin and other clotting factors". What would you say to that person?

 

How does this relate to cholesterol?

 

Cholesterol is VITAL to our health and high cholesterol is NOT a disease in its own right (much like high insulin in a developing Type 2 D with IR)... the cholesterol is doing its job in the blood vessels... what we need to treat is the underlying cause, the inflammation... in our case most likely a result of high BG levels (glucotoxicity).

 

 

The way to avoid scabs is to avoid falling off your bike NOT by reducing the ability of your body to do its work of healing itself.

 

---

 

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jps

Absolutely Frank.

 

It's been documented that approximately 90% of our total cholesterol is made in the liver, only 10% is dietary. Then why in the heck are we attacking the dietary portion of this equation?

 

I believe the recommended daily allowance of cholesterol is about 300 mg per day, give or take a bit depending on age. One freaking hard boiled egg has about 250 mg of cholesterol. So cook two eggs over easy in butter and you are WAY over the daily allowance in just one meal!!!

 

Obviously, most people are going WAAAAY over the recommended daily allowance, yet most people do not have cholesterol issues. And with the dietary variable only controlling 10% of the equation, why is that being attacked? It's non-sensical.

 

Something else has gone awry to make for the high cholesterol. Now, some people do have genetic issues that lead to hyperlipidemias, so I'm not counting them. I'm talking about the general population.

 

My guess is that the metabolic pathways are severely compromised from poor food choices and one of the byproducts of these choices is high cholesterol. But those poor choices, in my opinion, are not foods with cholesterol - since that makes up a mere 10% of our total cholesterol. Otherwise we'd be seeing the cholesterol problem increasing exponentially as we see with T2 diabetes.

 

As you said, cholesterol is absolutely essential to the human body. It's the precursor to many of our hormones, a huge component of vitamin D, bile, the myelin sheath of nerves and it is the hydrophobic component of our cell membranes.

 

When you look at a lipid profile, which item is it that is not critically essential to human function? Which item is it that we overconsume the most???

 

Again, this is just my opinion but dear God it seems sooooooo logical that it's not even funny.

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