Cystine Quantitative Plasma Test

This test measures the amount of cystine in your blood. 

• The Cystine Quantitative Plasma test is done to help diagnose cystinosis, a rare genetic disease.
• This test is also done to know if there is any risk of developing this disorder.

Your physician may recommend this test if you have

• Increased thirst and urination.
• Poor growth or delayed puberty.
• Muscle deterioration and weakness.
• Eye photosensitivity and pain.
• A family history of cystinosis.

Abnormal results may indicate higher levels of cystine which can cause harmful crystal deposits in organs, leading to diseases like cystinosis, Fanconi syndrome, or lupus erythematosus.

The test involves taking a blood sample from a vein using a sterile needle. The area will be cleaned with an antiseptic solution before inserting the needle. After collecting the sample, pressure will be applied to stop the bleeding. The entire procedure takes less than 5 minutes.

Follow your doctor’s recommendations for fasting before the test as it may affect the results. They may also ask you to stop taking certain drugs like penicillamine, cysteamine, and amino acid supplements before the test. It is advisable to consult your healthcare provider to determine if there are any particular requirements you should be aware of.

Additional tests that may be recommended by your physician include the following:

• Ophthalmologic examination
• Kidney function tests
• Urine analysis
• Molecular genetic testing

Cysteine/cystine measurement in plasma or plasma cystine assay

Cystinosis is a rare genetic metabolic disorder caused by an accumulation of cystine crystals in tissues and organs due to defective transport of cystine out of lysosomes. This condition usually affects the kidneys first, and will later cause eye and muscle damage if left untreated.