albumin and calcium

[LoveMedicine100]

Can someone explain relationship between calcium and albumin and an easy way to calculate the corrected calcium? i'm lost on this.

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[Bigeminy]

In the body, calcium is either bound to albumin or is found in its free form (ionized). It's the ionized calcium that you are concerned because ionized calcium is the physiologically active form of calcium; calcium bound to albumin is inactive. Standard lab tests are measuring the total calcium, unless you get a special ionized calcium level.

When albumin is low (nephrotic syndrome, compromised liver function, etc) you have a lower total calcium on lab tests due to less albumin. Total calcium = ionized calcium + calcium bound to albumin.

You can correct for this perceived calcium deficit with this formula:

Corrected calcium = serum total calcium + 0.8* (4 - serum albumin)

 

[Stellar Clouds]

Also albumin is negatively charged, hence the attraction between it and calcium.

 

[Bigeminy]

Also albumin is negatively charged, hence the attraction between it and calcium.

Yeah, that's the same reason why alkalosis can cause hypocalemia. When the serum is alkalotic, hydrogen ions bound to negatively charged albumin are released. These binding spots on albumin are now open for ionized calcium to bind, which reduces the amount of physiologically active calcium. This is why alkalosis can give you symptoms of frank hypocalcemia even though total serum calcium is unchanged on a lab test.

 

[sunnylomz]

Hi everyone
Late to the conversation. When I was looking for the corrected calcium formula, I see a site http://correctedcalcium.com/ says that "You may skip it if the albumin level is normal i.e. 4 or above".
My question is, if it is right to skip the steps of correcting the calcium if the albumin level is above 4?

 

[hfwm]

1. I think that's a myth. "Correction" should be done at any albumin value. A high albumin will obviously elevate the total calcium just as a low albumin does the opposite. Exactly one study had findings that suggested one should not correct total calcium for high albumin, but its findings were never replicated.
2. A bigger problem is that albumin-corrected calcium has been repeatedly shown to be poor at deducing ionized calcium status at any albumin value. Here is a link to a much better--and externally validated--method for deducing ionized calcium status:
qxmd.com/calculate/calculator_704/predicting-ionized-hypocalcemia-in-critical-care

 

[gyngyn]

1. I think that's a myth. "Correction" should be done at any albumin value. A high albumin will obviously elevate the total calcium just as a low albumin does the opposite. Exactly one study had findings that suggested one should not correct total calcium for high albumin, but its findings were never replicated.
2. A bigger problem is that albumin-corrected calcium has been repeatedly shown to be poor at deducing ionized calcium status at any albumin value. Here is a link to a much better--and externally validated--method for deducing ionized calcium status:
qxmd.com/calculate/calculator_704/predicting-ionized-hypocalcemia-in-critical-care

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