KNOWLEDGEBASE - ARTICLE #1288
EC50 values are blank.
This problem can occur when: you create (or save) a file in Prism 5.01 and open the file using Prism 4.
It only happens when you fit data to one of the following equations chosen from "Classic equations" list:
The problem is that Prism 4 tries to recalculate the EC50 from the LOGEC50. But Prism 5 saved it as "LogEC50" which Prism 4 does not recognize, due to the lower case letters. So Prism 4 leaves the EC50 blank, but reports the other values.
There is an easy fix. From Prism 4, click Change...Analysis parameters. Don't change anything, just click OK. Prism 4 now works fine. If you have lots of results pages with missing EC50 values, it seems as though the Recalculate All command should fix them all at once, but in fact that will not fix the problem. You need to OK the dialog for each analysis separately.
It is easy to avoid this problem. Instead of choosing an equation from the classic list, choose it from one of the dose-response or binding equations lists in Prism 5. Those will open fine in Prism 4 as a user-defined equation. The problem only happens with equations chosen from the classic list.
It only happens when you fit data to one of the following equations chosen from "Classic equations" list:
"Sigmoidal dose-response"
"Sigmoidal dose-response(variable slope)"
"One site competition"
"Two site competition"
"Sigmoidal dose-response(variable slope)"
"One site competition"
"Two site competition"
The problem is that Prism 4 tries to recalculate the EC50 from the LOGEC50. But Prism 5 saved it as "LogEC50" which Prism 4 does not recognize, due to the lower case letters. So Prism 4 leaves the EC50 blank, but reports the other values.
There is an easy fix. From Prism 4, click Change...Analysis parameters. Don't change anything, just click OK. Prism 4 now works fine. If you have lots of results pages with missing EC50 values, it seems as though the Recalculate All command should fix them all at once, but in fact that will not fix the problem. You need to OK the dialog for each analysis separately.
It is easy to avoid this problem. Instead of choosing an equation from the classic list, choose it from one of the dose-response or binding equations lists in Prism 5. Those will open fine in Prism 4 as a user-defined equation. The problem only happens with equations chosen from the classic list.
Keywords: IC50 missing