Cornstarch load test

A cornstarch load test is a test to measure the changes in your child’s blood sugar level after eating uncooked cornstarch. Cornstarch is a starch which is slowly digested to release glucose.

Why does my child need one?

Children with glycogen storage diseases tend to have this test. These children need feeding constantly to maintain their blood sugar at a safe level. This test shows how long it takes for the blood sugar level to reduce, which can influence the number of daytime feeds needed.

What happens before the test?

You will already have received information about how to prepare your child for the test in your admission letter. Your child will be admitted to the ward on the afternoon before the test is due. This is so the doctors and nurses can prepare your child for the test, which starts in the early morning.

The doctors will explain about the test in more detail, discuss any worries you may have and gain your consent for the test. If your child has any medical problems, particularly allergies, please tell the doctors about these. Please also bring in any medications your child is currently taking.

Your child will need to have a cannula (a thin plastic tube) inserted into a vein so blood samples can be taken more easily. A nurse will apply some local anaesthetic cream first so that the skin is numb.

During the night, your child will have their usual overnight feed, but this will be stopped at 8.30am so the test can start.

What does the test involve?

Within 15 minutes of stopping the night feed, a nurse will take a small sample of blood from the cannula. Your child will also be given a small amount of food with the cornstarch mixed into it. Your child will not be allowed to eat anything during the test, and will only be allowed to drink water.

Your child’s blood sugar level will be checked every hour by taking a small sample of blood from the cannula. This will continue for the duration of the test until your child’s blood sugar level drops to a stipulated low level. This could take up to eight hours and during this time your child will need to stay on the ward so the nurses can keep a close eye on him or her.

Once the test has been stopped, your child will be given a sugary drink to return their blood sugar to normal levels. Once this is achieved it will be safe to remove the cannula.

Are there any risks?

There is a very small risk that your child’s blood sugar level could drop to a dangerously low point, but as he or she will be closely watched on the ward, this is unlikely to happen. The nurses will stop the test if they are at all concerned about your child and give appropriate treatment for the low blood sugar.

Your child will probably feel tired and miserable during the test because he or she will not be allowed to eat as usual. It is important to continue the test so we can get accurate results. However tempting it is, giving your child food or drink other than water will mean the test will need to be stopped and rescheduled for a later date.

What happens afterwards?

Once the test has finished, your child will be able to eat and drink as normal. After he or she has been checked by a doctor, you and your child will be able to return home.

When you go home, you should call the ward or your GP if your child:

  • becomes generally unwell

  • refuses to eat or drink

  • starts to vomit

  • is unduly sleepy or difficult to wake

How long will it take to get the results?

Your child’s test results will be given to you at your next outpatient appointment at the hospital. However, if there is a need to start on new treatment before the appointment, the hospital will contact your family doctor (GP).

Compiled by: 
Kingfisher Ward in collaboration with the Child and Family Information Group This information does not constitute health or medical advice and will not necessarily reflect treatment at other hospitals.
Last review date: 
April 2014
Ref: 
2014F0368

Disclaimer

Please note this is a generic GOSH information sheet. If you have specific questions about how this relates to your child, please ask your doctor. Please note this information may not necessarily reflect treatment at other hospitals.