# National Cancer Institute drug screening. growth inhibition parameters??

### #1

Posted 12 May 2011 - 03:58 AM

Can someone please help explain the following calculations carried out by the NCI 60 cell line screen when testing drugs.

They initially plot a percentage growth inhibition curve using the following equations

Percentage growth inhibition [(Ti-Tz)]/C-Tz x 100 when Ti > Tz

Ti = absorbance after drug treatment Tz = absorbance at time zero, C = absorbance of control growth.

When Ti< Tz they dont factor the absorbance of the control growth and just use the equation [(Ti-Tz)]/Tz x 100 to calculate percentage growth inhibition

Can someone explain why the control growth is not considered when Ti < Tz surely if Ti is less than Tz its not cell inhibition but cells killed?

The url is below for full explanation

http://dtp.nci.nih.g...btb/ivclsp.html

Im lost!!

Any help would be great.

### #2

Posted 16 May 2011 - 07:13 AM

Anyone got anything?? even a reference to some good basic cell viability books/ sites?Hi All

Can someone please help explain the following calculations carried out by the NCI 60 cell line screen when testing drugs.

They initially plot a percentage growth inhibition curve using the following equations

Percentage growth inhibition [(Ti-Tz)]/C-Tz x 100 when Ti > Tz

Ti = absorbance after drug treatment Tz = absorbance at time zero, C = absorbance of control growth.

When Ti< Tz they dont factor the absorbance of the control growth and just use the equation [(Ti-Tz)]/Tz x 100 to calculate percentage growth inhibition

Can someone explain why the control growth is not considered when Ti < Tz surely if Ti is less than Tz its not cell inhibition but cells killed?

The url is below for full explanation

http://dtp.nci.nih.g...btb/ivclsp.html

Im lost!!

Any help would be great.

### #3

Posted 09 March 2012 - 03:47 PM