## Lethal concentration (LC50) calculation

Occasional Contributor
Posts: 8

# Lethal concentration (LC50) calculation

[ Edited ]

guys i m just stuck with lethal concentration (LC50) calculation.

I used two drugs of  different concentrations as one dose in my experiment.i.e one is 250ug/L and other is 100mg/L both make one dose. how i write it and find LC50. problem is like

1.   250/100

2.   300/50

as units are different what should i do????

please guide me as soon as possible....

i am using SAS University Edition

Occasional Contributor
Posts: 8

## Lethal concentration (LC50) calculation

[ Edited ]

guys i m just stuck with lethal concentration (LC50) calculation.

I used two drugs of  different concentrations as one dose in my experiment.i.e one is 250ug/L and other is 100mg/L both make one dose. how i write it and find LC50. problem is like

1.   250/100

2.   300/50

as units are different what should i do????

please guide me as soon as possible....

i am using SAS University Edition

PROC Star
Posts: 7,674

## Re: Lethal concentration (LC50) calculation

Can you be more specific? It would help if you provide data steps that show an example of what you have and, based on that example, what you want and what decision rules were needed to make the calculations/determinations.

Art, CEO, AnalystFinder.com

Occasional Contributor
Posts: 8

## Re: Lethal concentration (LC50) calculation

``````Normally for Calculation of LC50 calculation firstly according to method we have to add dose concentration,total number of animals and then number of mortality like the example below.Here 2,4,6.. represents dose concentration. data A;
input dose n response;
cards;
2 50 10
4 50 25
6 50 35
8 50 40
10 50 45
;
proc probit log 10;
var dose n response;
run;````As i mentioned previously i am using two different concentrations as one dose.how I write them.problm is I have my dose concentration in this form220/50300/100400/150when i put this this doesnt work.(both are different drugs which are taken as one dose concentration)please reply me as soon as possible ````

Posts: 4,240

## Re: Lethal concentration (LC50) calculation

[ Edited ]

To just answer the one specific question "as units are different what should i do????"

Convert your data to a common unit. 1mg = 1000ug

Occasional Contributor
Posts: 8

## Re: Lethal concentration (LC50) calculation

i  am thinking too of converting them in unit. but problem is still how i write to doses at once to get LC
Occasional Contributor
Posts: 8

## Re: Lethal concentration (LC50) calculation

After conversion in one unit how to add dose concentration.
SAS Super FREQ
Posts: 3,839

## Re: SAS query

For one parameter, the lethal dose (50%) is the concentration for which the predicted probability is 0.5. So if you have two parameters, the lethal does would be a curve in parameter space for which the predicted probability is 0.5.  You can use the EFFECTPLOT statement in PROC LOGISTIC or PROC PLM to create a contour plot that shows the 0.5 probability contour. For examples, see "Use the EFFECTPLOT  statement to visualize regression models in SAS."

Discussion stats
• 7 replies
• 363 views
• 0 likes
• 4 in conversation