This one seems like an easy question but I don't know where to start. Please help!

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?

BLD 414?

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

So... make a ratio and solve for x

.45/1.10mM = .55/x

Whatever x equals, add it to 1.10mM since we are looking for the total calcium in serum.

What do you think?

To estimate the total calcium in the specimen, you need to understand the concept of bound and ionized calcium in serum.

Bound calcium refers to the calcium that is attached to proteins like albumin, while ionized calcium refers to the calcium that is free in the serum and not bound to any proteins.

In this case, it is mentioned that about 55% of the total serum calcium is bound. This means that 45% of the total serum calcium is ionized or free.

Now, the measurement of ionized calcium with an ISE (Ion-Selective Electrode) is given as 1.10 mM. This represents the concentration of ionized calcium in the serum.

To estimate the total calcium, you can use the following formula:

Total Calcium = Ionized Calcium / (1 - Fraction of Bound Calcium)

In this case, the Fraction of Bound Calcium is 55% or 0.55. Plugging in the values, we get:

Total Calcium = 1.10 mM / (1 - 0.55)

Calculating further:

Total Calcium = 1.10 mM / 0.45

The estimated total calcium in this specimen is approximately 2.44 mM.

Remember, this is an estimate based on the available information. To get a more accurate measurement, laboratory tests specifically designed to measure total serum calcium should be used.