I was just tasked with adding anion gap to our panels.  I know there are a couple of calculations and wanted to know is one calculation better than the other?

Na-CL-HC03= anion gap or Na +K - CL- HCO3= anion gap.  I know that the reference ranges will be a little different between the 2 calculations, also are there any correction factors based on the albumin or phosphate results? 

Or is it just up to the physicians on which on to use and add a notation to the results about the impact that a low albumin could have on the results?

Thanks

 

I believe the use of potassium in the calculation is not common, as the effect of its inclusion is negligible.

Scott

On ‎1‎/‎3‎/‎2018 at 8:21 AM, SMILLER said:

I believe the use of potassium in the calculation is not common, as the effect of its inclusion is negligible.

Scott

Scott, do you know the reason why the K result is considered negligible in the anion gap calculation?

Is it because the K result is usually a much smaller number in comparison? And if this is the case then

when the anion gap is at the border of the range, would the K result not make a difference there, at

least numerically, but with questionable clinical relevance?

I would suppose (after a quick bit of research), that since a K is only going to vary by only 1 or 2 mEQs, that its inclusion makes little clinical difference.  That's as long as the reference range is appropriate for whatever calc you are using (such as: 8-16 without K+, and 10-20 with it).

Actually now that I think of it, the original omission probably had to do with making the equation a bit easier to do on the fly.  I imagine that as people used to do it in their head before the advent of computerized analyzers and reporting systems that now give the anion gap automatically.

Scott