Cerebrospinal fluid (CSF) amino acid (MET01) is a quantitative assay that is fundamental to the investigation of several inherited metabolic diseases. CSF Amino Acid Testing (MET01) may also be used for assessment of Variants of Uncertain Significance (VUS) identified during genetic testing (e.g. Next Generation Sequencing or Capillary Sequencing Testing).
Amino acids are the basic structural units that comprise proteins and are found throughout the body. Many inborn errors of amino acid metabolism that affect amino acid transport and metabolism have been identified. Amino acid disorders can manifest at any age, but most become evident in infancy or early childhood. These disorders result in the accumulation or deficiency of 1 or more amino acids in biological fluids, which leads to the clinical signs and symptoms of the particular amino acid disorder. The clinical presentation is dependent upon the specific amino acid disorder. In general, affected patients may experience failure to thrive, neurologic symptoms, digestive problems, dermatologic findings, and physical and cognitive delays. If not diagnosed and treated promptly, amino acid disorders can result in mental retardation and death. Cerebrospinal fluid (CSF) specimens are highly informative for a subset of these conditions, such as nonketotic hyperglycinemia and serine biosynthesis defects. CSF specimens are most informative when a plasma specimen is drawn at the same time and the ratio of the amino acid concentrations in CSF to plasma is calculated. For epilepsies, CSF glycine measurement is often crucial to the diagnosis of glycine encephalopathy (GE), low CSF serine concentrations are characteristic of 3-phosphoglycerate dehydrogenase deficiency (3-PGDD) and the presence of sulphocysteine is pathognomonic of sulphite oxidase deficiency (SOD), and a vital clue to molybdenum cofactor deficiency (MCD). Additional disorders that can be diagnosed by CSF Amino Acids (MET01) include, but are not limited to, phenylketonuria, tyrosinemia, citrullinemia, non-ketotic hyperglycinemia, maple syrup urine disease, and homocystinuria. The assay is also key for the continued monitoring of treatment plans for these disorders and useful for assessing nutritional status of patients.