POZ Community Forums

Main Forums => Living With HIV => Topic started by: gvolts5 on December 01, 2006, 12:18:08 am

Title: mm3 and mL
Post by: gvolts5 on December 01, 2006, 12:18:08 am

Why do we count the VL per mL and the CD4 cell count per mm3?

John

Title: Re: mm3 and mL
Post by: Eldon on December 01, 2006, 11:24:06 pm

Hey Gvolts5,

 You May Want To Start here (http://www.aidsmeds.com/lessons/StartHere1.htm)


Make the BEST of each Day!

Title: Re: mm3 and mL
Post by: gerry on December 02, 2006, 12:42:21 am

Hmmm.  Never thought of that question before.  I think you need a relatively bigger unit volume (1 mL = 1 cubic centimeter = 1000 cubic millimeters) in order to accurately measure viral load that goes all the way down to <50 (minimum level of detectability is 50 copies) to all the way up to 750,000 to 1,000,000.  If one reduces the unit volume to per cubic millimeter or microliter, then <50 VL may not mean a whole lot.

Title: Re: mm3 and mL
Post by: HIVworker on December 02, 2006, 03:18:34 am

Isn't it because FACS (used to measure CD4's) works on mm3 because of the way it counts? Viral load is measured in terms of virions per ml because viral titers are measured that way. As in Infectious units per ml.

R

Title: Re: mm3 and mL
Post by: gerry on December 02, 2006, 01:36:16 pm

You're most likely correct, Rich.  I thought he was asking why the units were calibrated that way for the test kit/equipment in the first place.  Don't really know the answer to that.  The "per unit volume" is interchangeable; mL can be converted to mm3.  But it would not make sense, for instance, for a viral load to be reported as per mm3 because a viral load of "50 copies per mL" would convert to "0.05 copy per mm3" so it makes much more sense to use mL as the unit volume for reporting viral loads.  Nice food for thought on a slow news day.

Title: Re: mm3 and mL
Post by: gvolts5 on December 02, 2006, 06:09:41 pm

Never mind, this question is not important.  The literature usually uses mL when discussing Viral Load.  I think I found one website that used mm3, but from what I can tell it's more standard to use mL.

Maybe I'm on the wrong website for these types of questions.  I've noticed that there isn't a forum here that discusses this kind of stuff.  Posting here in "Living with HIV" may not be the place for this kind of talk.

John

 

Title: Re: mm3 and mL
Post by: gerry on December 02, 2006, 07:41:39 pm

So sorry you're not getting your answers here.  There's a couple of websites where you can ask experts your questions: The Body.com (http://www.thebody.com/experts.html) and Hopkins (http://www.hopkins-aids.edu/ask.html).  I'm sure there are others.  Archives in thebody.com are searcheable, while those in Hopkins are indexed (there's a Basic Science link in QA by categories that have answers to a some of the questions that you have in the other thread you started as well.

Title: Re: mm3 and mL
Post by: HIVworker on December 02, 2006, 11:00:46 pm

Well, I wonder why you are asking this question. If it is for a conversion, then 1 mm3 = 1 microliter (or 1/1000th of a ml).

Rich

Title: Re: mm3 and mL
Post by: gvolts5 on December 03, 2006, 07:13:11 am

Thanks for the websites!  I probably could have searched around myself but sometimes it might take a while to find what you're looking for then you end up getting distracted by some other interesting topic.  You know how surfing can be. 

Here's an interesting webcast lecture from the NIH which you've probably seen, "HIV Evolution, Can it Be Stopped?":

http://videocast.nih.gov/ram/iig051502.ram

thanks,
John