Platform
Company
Body Fluids
Review status
Currently under review
Pending specialist review and validation.
CSF histidine measures the amount of the amino acid histidine in the cerebrospinal fluid, the clear liquid that cushions your brain and spinal cord. The sample is collected during a lumbar puncture and is often analyzed together with other CSF amino acids.
Histidine is a building block of proteins and a precursor to important molecules, including histamine and carnosine. Measuring it in CSF helps your care team assess amino acid metabolism and transport within the central nervous system, which can differ from what appears in blood.
Your clinician may order CSF histidine when evaluating unexplained neurologic symptoms such as seizures, developmental concerns, encephalopathy, or when an inborn error of metabolism is suspected. It can also be useful when brain inflammation or injury is being evaluated and when comparing CSF with blood helps clarify whether a change is centered in the brain or reflects a whole‑body process.
Findings can guide diagnosis, support decisions about diet or medications, and help monitor response to therapy. The test itself carries minimal risk beyond that of the lumbar puncture, and it can provide meaningful clues about brain chemistry without requiring more invasive procedures.
CSF histidine results are interpreted in the context of your symptoms, exam findings, and other laboratory data. A result that is higher or lower than expected does not diagnose a condition on its own. Your team will often compare CSF findings with plasma amino acids and review other CSF measures such as protein and cell counts to see the full picture.
Small deviations can occur with recent seizures, mild inflammation, or sample handling issues. If a significant or persistent change is found, your clinician may recommend repeat testing, concurrent plasma testing, targeted metabolic studies, or referral to a metabolic or neurology specialist. Next steps focus on the underlying cause and may include nutrition guidance, medication adjustments, or other supportive care.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Mixing of blood with CSF during a traumatic tap can artificially raise amino acid readings, including histidine. Careful collection and noting visible blood help your team interpret results accurately.
Amino acids can shift if CSF is not promptly cooled and frozen or if bacterial growth occurs. Using the correct tube, rapid transport on ice, and quick freezing of aliquots reduces pre‑analytic changes.
Seizures, stroke, or central nervous system inflammation may transiently alter CSF amino acids. Let your clinician know about recent events, treatments, and timing relative to the lumbar puncture.
High protein intake, parenteral nutrition, or severe malnutrition can change blood amino acids and influence the gradient between blood and CSF. Concurrent plasma testing improves interpretation.
Antiepileptic drugs, corticosteroids, and amino acid supplements may shift amino acid patterns. Provide a complete list of prescription, over‑the‑counter, and herbal products before testing.
Newborns and infants have different amino acid handling and blood‑brain barrier characteristics. Age‑appropriate interpretation and comparison with plasma are often needed.
References