Drawing cell count off of PD cath

I work in the ED. I had a pt last night whom developed a fever 3 days after realizing her PD catheter cap was off for a day. I have had no experience with PD cath's until now and felt incompetent with the whole situation. I didn't feel too bad because the doc told me she wanted a specimen of the peritoneal fluid sent lab for a cell count and cx., and said she guessed I could just draw off of the cath for it. I went in to ask the pt about how they have done this in the past for her and she was not too sure. I called up to the hospital dialysis floor and the RN I spoke to said the pt would have to be hooked up to drain to obtain a specimen. I talked to the rapid admit RN (whom eventually came down to drain the pt, being her time to drain was near anyway) and she said it must be done this way because you can pull fibrin and other contents into the specimen if you have trying to just draw back on the catheter with a syringe as well as disrput the pressure inside the cavity causing spasms or something I guess. I need to look at the hospitals P&P for this but I was wondering how anyone else has done this. Can you draw up with a syringe to obtain the 8 to 10cc you need for specimen collection, or would you have to drain the pt all together? Thanks!!