Homocysteine Analysis

Clinical Information

Homocysteine is a non-protein amino acid that is synthesized through the conversion of methionine. Elevations in plasma homocysteine levels may be associated with homocystinuria, cobalamin disorders (cblC, cblD, and cblE), and vitamin B12 or folic acid deficiencies.

The symptoms of homocystinuria include lens dislocation, osteoporosis, skeletal abnormalities such as genu valgum or a pectus deformity, thrombotic events, intellectual disability and psychiatric/behavioral disturbances. However, the phenotype is variable. Certain cobalamin disorders (CblC, CblD and CblE), which are characterized by hypotonia, failure to thrive, developmental delay and megaloblastic anemia, also result in elevated homocysteine levels. Measurement of plasma homocysteine can be used to monitor patients undergoing treatment for these conditions.

Technical Information

Plasma homocysteine levels are measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Specimen Requirements

• Plasma is the accepted sample type for this test. Collect a minimum of 3 mL whole blood in a sodium heparin tube.
• Or blood can be centrifuged and a minimum of 1 mL plasma removed and sent for analysis. Plasma should be isolated from whole blood within four hours of collection to avoid false elevations of homocysteine.

Transport Instructions

Plasma should be frozen after collection and shipped frozen, preferably on dry ice. Whole blood should be shipped at ambient temperature.