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TCID50 calculation

David Richard Harper D.R.HARPER at MDS.QMW.AC.UK
Sun Jan 12 13:37:33 EST 1997

Ian A. York wrote:
> I'm embarassed to have to ask this question.  Fortunately, I'm used
> to making a fool of myself.
> I want to calculate a TCID50.  I've done serial ten-fold dilutions
> of my virus, five wells per dilution.  At 10e-8 all five wells show
> CPE; at 10e-9, two of five wells show CPE; none of the wells at
> 10e-10 show CPE. I know that you can calculate TCID50 from this
> according to the method of Karber, and in fact I have a paper which
> spells out the formula.  Problem is that the paper is so poorly
> written at this part that the formula doesn't make sense to me. 
> (The real problem is that the bozo who wrote the paper was me.  At
> the time I had the formula sitting beside me, used it every day, and
> took it for granted that I would never forget it.  Let that be a
> lesson to me.)  (The rest of the paper isn't as bad, I'll say in my
> own defense.) (It was my first, okay?)
> So.  Anyone feel like spelling it out to me?  Thanks.
> Ian "bozo" York
> --
>       Ian York   (iayork at panix.com)  <http://www.panix.com/~iayork/>
>       "-but as he was a York, I am rather inclined to suppose him a
>        very respectable Man." -Jane Austen, The History of England

Formulae for both Reed-Muench and Karber TCID50's are given in chapter
5 of "Virology Labfax", Bios Publishers (plus Academic Press in the US
or Blackwell worldwide), 1993, edited by me.  Personally, I use plaque
counts and don't use either, but there you go...

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