Asked by Jesse

I have 2 questions relating to clinical chemistry...

1st:
I have no idea where to even start with this. It seems like it should be simple, but I have no clue.

The question is...

"In serum, about 55% of total serum calcium is bound. The measurement of ionized (free) calcium with an ISE is 1.10 mM. What is an estimate of the total calcium in this specimen?"

My guess is since 55% is bound, that means 45% is free ionized species.

So... .45/1.10mM = .55/x

Solve for x and add to 1.10mM??

2nd:
I have no idea as to any reasons why this might occur...

Why is slightly higher serum sodium consistently found by evaluation by ion-selective electrode (ISE) as compared to flame photometry?



Any help would be greatly appreciated. Thank you!!
Answered by DrBob222
Isn't percent just (amount/total)*100 = 45. So
(1.10/total) = 0.45. Solve for total.
Answered by Jesse
Thank you... Any ideas on ISE vs. flame photometry?

I was thinking that maybe flame photometry comes out consistently slightly lower because it is hard to standardize? I mean, its hard to get the exact temperature of the flame to be precise (and accurate)?
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