Reference Range(s)

[lydgate]

Does anyone know of research that has been done on inter-national or inter-ethnic variations in the reference ranges provided for lab tests, specifically the CD4 and CD8 counts? A positive friend from India gets his blood-work done at a highly reputed (and expensive) private laboratory. This is what the lab in question provides as the 'normal' reference range:

CD4 %: 26 – 48

ABSOLUTE CD4: 354 – 1100

CD8 %: 18 - 41%

ABSOLUTE CD8: 192 - 980

CD4/CD8 RATIO: 0.57 - 2.03

Since 'normal' is essentially a statistical concept, I'm assuming that the lab has based its upper and lower limits on the samples it actually receives. Is this a foolish assumption on my part? Second, I'm struck by the lower limit of 'normal' in all these values -- significantly below the standard lower limit one finds in American/European lab results. For example, absolute CD4 lower limit as 354 (instead of circa 500), and ratio 0.57 instead of 0.9 or 1. Likewise, the upper limit is given as 1100, not 1500 etc.

Any thoughts, comments on this?

Jay

[bocker3]

A reference range SHOULD be calculated using the local population, although, increasingly laboratories do tend to use "standard" reference ranges.  The danger with that approach is that a clinical parameter CAN be different based on where you live, what you eat, etc, etc.

For example -- The reference ranges for things like Red Blood Cell count, Hemoglobin and Hematocrit should be quite a bit lower in people who live in areas that are at sea level when compared with a population who lives in an area, like Denver.  There is less oxygen at higher altitudes, so the body compensates.

Finally it may sound like nitpicking, but one should try to avoid equating the term "reference range" with normal.  A reference range is based on a population while "normal" is really individual.  What is "normal" for you may not be normal for me.  So, I don't agree that "normal" is a statistical concept, but it is true for a reference range.

As for the lower limits your friend's lab uses:

When I was having my labs down by LabCorp the Absolute CD4 ref. range was 359 - 1519.
When I started going to Quest Labs (insurance requirement) the range change to 490-1740.
LabCorp did the testing in NC.  Quest does it in MD.

At the end of the day, the reference ranges aren't all that meaningful for HIV+ folks, as we should never be included in a population that would be used to assess a CD(insert #) reference range -- what's key is keeping our CD4's up over where there can be actual clinical manifestations, i.e. OIs.
Hope that helps!

Mike

[bobino]

For what it may be worth, the lab my doctor uses here in San Francisco considers the bottom range of a "normal" CD4 count to be 400.  Also, according to this lab, the lowest "normal" CD4% is 35%.

So, my latest CD4 count of 496 falls within the normal reference range, whereas my CD4% of 34 is abnormally low, at least according to this lab.

[anniebc]

Hi Lydgate

Not sure if this helps, just FYI really,  but the so called "Normal Ranges" here in Australia/NZ are:

CD4%..27 - 56

AB CD4..320 - 2000

CD8..11 - 35

AB CD8..130 - 1220

CD4/8 Ratio..1.00 - 3.50



Hugs
Jan