Hi Philippe,
Well, that's rather easy then.
Check the value of ApplicationServices.Application.VersionBuild , and compare to the build version for each release.
Here's a handy reference: https://knowledge.autodesk.com/support/revit-products/downloads/caas/downloads/content/autodesk-revit-2016-product-updates.html?_ga=1.106393987.1856407908.1457529717
-Matt