dialogue: Donica: I came to this lab to have my blood drawn.
  Ally: You are in the right place. Roll up your left sleeve and have a seat.
  Donica: What am I being tested for?
  Ally: Your doctor wants to know what your white blood cell count is.
  Donica: What does my white blood cell count tell him?
  Ally: Usually if your white count is off, the doctor suspects an infection.
  Donica: How much will it hurt?
  Ally: It is only a pin prick. I have to put this tourniquet on your arm to make the vein easier to find.
  Donica: Is that my blood going into that tube?
  Ally: That blood that just filled the tube is all that I needed. Thanks for coming in!
summary: Ally is drawing Donica's blood as the doctor wants to know Donica's white blood cell count.