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