Amino Acids (CSF, Plasma & Urine)

Clinical Use: CSF: CSF amino acid analysis is fundamental to the investigation of several inherited metabolic diseases particularly those presenting with unexplained seizures.

Low levels of glycine can aid diagnosis of glycine encephalopathy and decreased serine may point to deficiency of 3-phosphoglycerate dehydrogenase.

The presence of sulphocysteine is pathognomonic of sulphite oxidase deficiency.

Plasma & urine: Clinicians use amino acid anomalies to diagnose and subsequently manage therapy in inborn errors of metabolism and other conditions.

Further use is in the evaluation of acquired conditions, including endocrine disorders, liver diseases, muscle diseases, neoplastic diseases, neurological disorders, nutritional disturbances, renal diseases, and burns.

Background: Amino acids are the basic structural units that comprise proteins and, as such, are found throughout the body. Amino acid disorders are caused by impaired metabolism or transport of proteins and amino acids. This results in the accumulation or the deficiency of one or more amino acids in biological fluids.

Inborn errors of amino acid metabolism can manifest themselves at anytime, but most become evident in infancy and early childhood. Specific symptoms are dependent upon the type of amino acid disorder.

Affected patients may have failure to thrive, neurological symptoms, digestive problems, retardation, and a wide spectrum of laboratory findings. If not diagnosed promptly and treated properly, these disorders can result in poor growth, developmental delays, mental retardation, and death.

Many amino acids are synthesized by the body and are referred to as nonessential. Essential amino acids, however, must be obtained through an individual’s diet. Treatment for amino acid disorders typically involves very specific dietary modifications, which must be coordinated and closely monitored by a dietician or physician and involves periodic amino acids analysis.

Urine and serum are the usual matrices for amino acid measurement when an inherited metabolic defect is suspected. However, in the conditions listed above critical diagnostic information can be obtained by examining the amino acid profile in CSF.

Reference Ranges: CSF: Available from the referral laboratory
Plasma & Urine: Provided with results
Associated Diseases:
Patient Preparation: None required
Specimen Requirements: CSF: Specimen collected into a plain universal container
Plasma: Blood specimen into a Lithium heparin (dark green top) or SST or paediatric heparin tube
Urine: Random urine sample – about 25ml in a plain universal container
Turnaround Time: CSF: 10 working days
Plasma: 10 working days
Urine: 2 weeks
Additional Information:
Referred Test: Referred test
Location: Royal Victoria Infirmary