I personally would not do it for lyme testing. I've had two taps and both were bad. I'm not saying you shouldn't but it's no picnic. Some people breeze right through it but I'm a very difficult tap and got admitted for the headache the last time. I think an Igenex western blot, along with a low CD 57 would be diagnostic.
I figured that LLMDs have better statistics on the East coast than on the West coast where I live, so I'm trying to take advantage of this web site to see what they say and find more of a consensus. From my experience, even for non-controversial diseases, the doctors don't agree very well! (BTW, my neurologist sees no benefit (in my case) of doing LP for neuro disorders/MS so in this case, I would be doing it specifically for Lyme testing.
If I recall correctly it's about 10-20% reliable even with a positive case of lyme. It's good to rule in or out other conditions like MS.
Very little can be seen in a LP. Painful and useless. You should read "Cure Unknown".
Most ID specialists deny the very existence of chronic Lyme, so if you like to waste your time and be told "it's all in your head", then get an appointment with one of those!