Tracking cystine levels
What is a cystine level test?
Cystine level testing measures the amount of cystine in white blood cells
(WBCs). Along with carefully following a treatment plan, routine testing is key. Testing is the only way to know a person’s cystine level.
Why cystine level testing is important
Tracking cystine levels over time helps people and their doctors know how well their treatment is working. Knowing a person’s cystine level will help a doctor decide if a dose needs to be adjusted. Having the correct dose is the only way to help delay or limit damage to the body.
Two cystine tests. Two target levels.
There are two types of cystine level tests. They measure cystine levels differently.
| Type of WBC cystine level tests | Mixed leukocytes test | Granulocytes test |
| Target cystine level range | Below 1.0 nmol ½ cystine/mg protein | Below 1.9 nmol ½ cystine/mg protein |
| When to get the test | The doctor will order WBC cystine level testing as they feel is appropriate. | |
It's important to work with a doctor to decide which cystine level test is right for you. Always know which test is being taken: results mean different things with different tests. The same test should be taken each time to help compare test results over time.
Timing matters
It's important to have cystine levels tested at the right time to get useful test results. Ask your doctor what time of day to get your cystine levels tested.
