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Is there a problem with the Iranian cholesterol calculator?

Commented on October 04, 2013
Created October 03, 2013 at 3:34 PM

I got blood tests done, as mentioned in another post, and I was looking around for info on Paleo LDL, and one thing I found was that for people with low triglycerides, the "Iranian" formula is a better way to calculate LDL.

There is a calculator online that you can either fill out in mmol/L units, or use the mg/dL version

I'm in Canada, so my results are in mmol/L, but I didn't see the mmol version initially, so I converted my readings using this calculator. Here are my readings in both formats:

Total Cholesterol: 4.83 mmol/L

Total Cholesterol: 86.94 mg/dL

HDL Cholesterol: 0.99 mmol/L

HDL Cholesterol: 17.82 mg/dL

Triglycerides: 0.74 mmol/L

Triglycerides: 13.32 mg/dL

Okay, so everything looks fine so far: The numbers are proportionate and the conversion from mmol to mg seems correct. But when I plug these into the calculator I get this:

LDL = 66.45 (mg/dL) as per Friedewald formula LDL = 25.86 (mg/dL) as per "Iranian" formula LDL = 3.498 (mmol/L) as per Friedewald formula LDL = 3.092 (mmol/L) as per "Iranian" formula

Look at that disparity! When measuring in mg/dL, my calculated LDL goes down by maybe 15%, but when measuring in mmol, it goes down something more like 60% !!

Is there a reason for this, or is the calculator just broken? And more importantly, if it is broken, which of these 2 scenarios is the actual correct one?

32f5749fa6cf7adbeb0b0b031ba82b46

(41787)

on October 04, 2013
at 02:41 AM

Ahh, I see what you're getting at. I take for granted understanding moles, chemist brain. I generally describe it like a really big "dozen".

3ce6a0d24be025e2f2af534545bdd1d7

(26197)

on October 03, 2013
at 11:40 PM

right. I was using density as an analogy. mole can be a very difficult measurement to grasp. I only needed to take 2 semesters of chemisty (thank God) and while I get the reference to the number of atoms in 12g carbon -- it's still pretty abstract. I'd imagine to people who have had no chemistry course work, density is easier to grasp.

32f5749fa6cf7adbeb0b0b031ba82b46

(41787)

on October 03, 2013
at 08:05 PM

No density needed to convert from mmol/L to mg/dL, just the molecular weight of cholesterol, 386 mg/mmol.

3ce6a0d24be025e2f2af534545bdd1d7

(26197)

on October 03, 2013
at 06:51 PM

btw, here is a mmol/L calculator so you don't have to worry about conversions:

http://homepages.slingshot.co.nz/~geoff36/LDL_mmol.htm

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1 Answers

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3ce6a0d24be025e2f2af534545bdd1d7

(26197)

on October 03, 2013
at 06:35 PM

Yes, your math is wrong.

  • TC: 4.83 mmol/l = 186.77494 mg/dl
  • HDL: 0.99 mmol/l = 38.28306 mg/dl
  • Trig: 0.74 mmol/l = 65.54473 mg/dl

These numbers give you a 12% difference in LDL calculation (note, these numbers are within a rounding error of a straight conversion of your mmol/L values above so I have not modified them):

  • Friedwald: 135.3 mg/dL
  • Iranian: 118.6 mg/dL

On another note. A mathematical model is only accurate within the bounds that it was modeled. Friedwald was modeled to represent less than a 10% error for trigs between 100 mg/dL and 300 mg/dL. Iranian was modeled to represent less than a 5% error for trigs above 350 mg/dL. Neither are suited to estimate your LDL (although some studies show that Friedwald maintains its accuracy down to 70 mg/dL, and your values are only slightly outside it's bounds, so Friedwald may be more accurate), another reason it is so important to get a measured test and not an estimated test.

edit:

the calculator you used is for glucose. just as 16 oz of water weighs less than 16 oz maple syrup, density is an important factor in this conversion.

3ce6a0d24be025e2f2af534545bdd1d7

(26197)

on October 03, 2013
at 06:51 PM

btw, here is a mmol/L calculator so you don't have to worry about conversions:

http://homepages.slingshot.co.nz/~geoff36/LDL_mmol.htm

32f5749fa6cf7adbeb0b0b031ba82b46

(41787)

on October 03, 2013
at 08:05 PM

No density needed to convert from mmol/L to mg/dL, just the molecular weight of cholesterol, 386 mg/mmol.

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