5-Methyltetrahydrofolate (CSF)

18 days

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Cause for Rejection:
Gross blood contamination/hemolysis.

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Cerebrospinal fluid (CSF) 5-methyltetrahydrofolate (5-MTHF) is used to assess folate status within the central nervous system (CNS). Measurement of CSF 5-MTHF is the preferred approach for evaluating CNS folate metabolism, as peripheral folate concentrations may not accurately reflect brain folate status. CSF 5-MTHF testing is primarily indicated for the evaluation of cerebral folate deficiency (CFD) and relat ed neurologic disorders. CFD is characterized by reduced CSF 5-MTHF concentrations, often in the setting of normal peripheral folate levels, and may result from both primary genetic and secondary acquired conditions. Low CSF 5-MTHF levels are associated with a spectrum of inborn errors of metabolism and acquired disorders. Primary causes include proton-coupled folate transporter (PCFT) deficiency, FOLR1-related cerebral folate transport deficiency, dihydrofolate reductase (DHFR) deficiency, methylenetetrahydrofolate reductase (MTHFR) deficiency, and methyltetrahydrofolate synthetase (MTHFS) deficiency. Secondary causes include folate receptor alpha autoantibodies (FRAA), mitochondrial disorders such as Kearns-Sayre syndrome, serine biosynthesis defects, dihydropteridine reductase (DHPR) deficiency, aromatic L- amino acid decarboxylase (AADC) deficiency, and folinic acid-responsive seizures. Nutritional deficiency and some treatments (methotrexate) can also lead to low CSF 5-MTHF levels. This test may also support interpretation of variants of uncertain significance (VUS) identified through genetic testing, including next-generation sequencing, in genes involved in folate transport and metabolism.

Cerebrospinal fluid (CSF) from a lumbar puncture (LP)

0.5 mL

Labcorp 5-Tube CSF Collection Kit (recommended)

No special preparation is required for this test. You may eat, drink, and take your medications as normal, unless instructed otherwise by your healthcare provider.

Sample Collection and Handling Instructions Single-Tube Collection (if no additional testing is ordered): Collect the entire sample into a single sterile tube from a standard LP. IMPORTANT: If additional tests are ordered concurrently, use the LabCorp 5-Tube CSF Collection Kit (PS# 125218). Each kit contains five microcentrifuge tubes. CSF Collection Protocol Collect CSF starting from the first drop directly into the first tube. Do not aliquot from a pooled sample. Fill tubes in numerical order, to the volume listed below: - Tube 1: 0.5 mL - Tube 2: 1.0 mL - Tube 3: 1.0 mL (contains antioxidants to preserve sample integrity) - Tube 4: 1.0 mL - Tube 5: 1.0 mL Handling after collection: - If no blood contamination: --> Place tubes on dry ice immediately at bedside. - If blood contamination is present: --> Centrifuge immediately (before freezing) --> Transfer clear CSF to new, correspondingly labeled tube --> Then place the tube on dry ice immediately. Label tubes with patient name and ID number, leaving the tube number viewable. Complete LabCorp Neurochemistry request form. Include test required, sample date and date of birth.