What is the true intent of the initial drug screen at pain management?

[awickeddream]

I just began treatment at a new pain clinic. The doctor was a douche but made a big deal about my initial drug screen. What's the true intent of the initial screen? They can't hold against me medication I took before I started his treatment and before I signed a narcotic agreement when he hasn't even mentioned treating me with narcotics, right? And I explained what I took and how I obtained the rx. Please forgive me for my not using forum lingo. I'm new to having an account instead of just reading posts. I'm tripping because I literally have no other option than this doctor and live in severe pain daily. Also, how would I convince an anesthesiologist to treat me with narcotics as well as injections.

 

[FuckWithRaw]

To see what your taking and how much of it is in your blood so if levels go up they know your full of shit.
Not sure what your actually trying convince an anesthesiologist but I'm going to guarantee they won't listen to you.