Histidine Quantitative Serum Test

This test measures the level of histidine in your blood. 

• To diagnose various metabolic disorders or inborn errors of metabolism
• To monitor the effectiveness of treatment for metabolic disorders 
• To evaluate symptoms such as developmental delay, seizures, muscle weakness, and intellectual disability

Your doctor may recommend this test if you have

• Symptoms or provisional clinical diagnosis suggestive of a metabolic disorder or inborn error of metabolism.
• A family history of metabolic disorders.
• Developmental delay, seizures, muscle weakness, or intellectual disability.

Abnormal levels can indicate a variety of metabolic disorders or inborn errors of metabolism such as histidinemia, phenylketonuria (PKU), tyrosinemia, and hypermethioninemia. 

The test requires a blood sample to be drawn from the arm. The healthcare provider will use a needle and a syringe to collect the sample. The process takes a few minutes and may cause slight discomfort. 

• Consult with your doctor about medications and amino acid supplements that need to be stopped before the test.
• Fasting is recommended but not mandatory.
• Drink plenty of fluids and follow any other instructions provided by your doctor.

Other tests that may be ordered alongside the Histidine Quantitative Serum test include the following:

• Amino acid analysis 
• Organic acid quantification 
• Blood tests for other essential amino acids, such as phenylalanine and tyrosine

Histidine test or quantitative amino acid analysis

Histidinemia is a rare metabolic disorder that affects the breakdown of histidine in the body, leading to its accumulation in blood and urine. It can cause intellectual disability, developmental delay, seizures, muscle weakness, and behavioural abnormalities.