The documentary doesn't show anything new.
About 20 years back, the only way to be 100% sure was to do constant muscle biopsies, but since that would build up scar tissue, it never came to fruition.
There are some who wanted to define a baseline of several markers, like testosterone, red blood cells, growth hormone and the such, and everybody with more than that baseline would be disqualified.
How are athletes tested now? Blood and urine?