Tandem Mass Spectrometry
Serum or Plasma
UCSD Biochemical Genetics
2 mL Blood
Light Green (Lithium Heparin PST)
Urine is NOT acceptable. See Homocystein, Urine to Quest forwards to Mayo. Plasma collected in sodium heparin (green-top) or EDTA (lavender-top) tube is also acceptable. Serum collected in a red-top or serum separator tube (SST) is also acceptable but only as an alternative if needed.
1 mL Plasma
0.5 mL Plasma
Centrifuge, separate serum or plasma freeze promptly. Complete UCSD Biochemical Genetics requisition and submit with specimen frozen.
Where older methods only measured free homocystine, this method detects total (free and protein-bound, reduced homocystein and oxidized homocystine).
Elevation of homocysteine is diagnostic for homocystinuria, and has been associated with vaso-occclusive and thrombotic disease. Noted that this method does not detect homocystine in healthy subjects, so normal range is not directly comparable to that of older methods.