Corrected calcium level

[yoyohomieg5432]

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Can anyone explain what this is used for? There was a uworld question of somebody with hypocalcemia in nephrotic syndrome due to the low albumin. but then they calculated the corrected calcium. I'm not sure why you care to calculate that?

• Corrected Ca = [0.8 x (normal albumin - patient's albumin)] + serum Ca level

 

[justin1390]

Because when you measure serum calcium, it's total calcium. But if you're albumin is low, then calcium reads falsely low (albumin binds calcium). If you have a person with a a albumin of say 2 and a 8.9, the it looks like their Ca is essentially normal, right? But really, they are hypercalcemic, and the question may be looking for primary vs secondary hyperparathyroidism. It's easy: just add 0.8 of calcium for every 1 that albumin is less than 4.

Albumin is normally 4. Take their albumin and subtract from 4. So if it's 2.2, then 4 - 2.2 = 1.8. Now multiply by 0.8 = 1.44. If their calcium was 7.2 (looks low, right?) then 7.2 + 1.44 = 8.6. Basically normal.

Here's a couple more examples I ran across: