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Is there a problem with the Iranian cholesterol calculator?

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Updated about 9 hours ago
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?

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41544 · October 04, 2013 at 2:41 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".

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26182 · 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.

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41544 · October 03, 2013 at 8:05 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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26182 · October 03, 2013 at 6:51 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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26182 · October 03, 2013 at 6:35 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
26182 · October 03, 2013 at 6:51 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
41544 · October 03, 2013 at 8:05 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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