When my youngest was having problems and fears about getting blood in his SCIG line, a friend told me about social stories. We used this technique with great succes (along with the worry book I mentioned before). We would explain to Joseph that if he got blood in his line, we would take care of it and explain what would happen. This eased his fears. You can use social stories for helping your children cope with the many medical procedures and tests, too.
Here are a few links:
Social Stories, their use and Start