Your child may have many blood tests during treatment and follow up care, especially if chemotherapy is given.
Blood samples are taken to:
- perform RB1 genetic testing.
- monitor blood counts, and risk for infection during chemotherapy
- assess blood chemistry to monitor health of the liver and kidneys
- check for infection if your child has a fever
Blood may be drawn by a doctor, nurse or phlebotomist – a specialist technician whose main job is taking blood for testing. Phlebotomists are very skilled at taking blood samples from children.
Depending on the tests being done, blood can be drawn through a finger poke or from a vein.
A finger poke is usually sufficient for a simple CBC or to check blood glucose levels. The nurse or technician will hold a little device against the tip of your child’s finger. When they press a button, a small needle will pop out with a an audible click, and prick the finger.
They may gently squeeze the fingertip to manipulate blood flow. This can cause discomfort, but it is not usually painful. The blood will be collected in a small container that will be labelled with your child’s hospital details.
You can use a topical anaesthetic (a cream of gel) to numb the finger before the poke. EMLA, Ametop and Freezy Spray are the most common.
Freezy Spray is fast acting and can be sprayed on the finger immediately before the poke, but check ahead of time if it will be available in clinic on the day of your appointment. Ametop gel works in about 30 minutes and is available over the counter in many countries. EMLA cream may take upto 2 hours to work.
For best results, use EMLA 2 hours before your appointment, or Ametop about 40 minutes before. Once you have put the cream or gel on the pad of the finger tip, wrap the finger in cling film / saran wrap and tape it in place.
At the clinic or lab, unwrap the finger ad wipe it with a clean cloth. Ask for a warm pack to wrap around the finger, as this will encourage blood flow during the finger poke.
Encouraging your child to choose which finger she would like the nurse to collect the sample from gives her some choice and helps her feel involved.
Venous Blood Draw
Blood chemistries and cultures can only be done with blood from a vein in your child’s arm, or from their central line.
Taking blood from a vein uses the same process as inserting an IV, but the needle is removed after the blood draw. If your child has a central line, you can request it be used instead of looking for a vein in the arm.