Homocysteine, plasma or serum

Lab area

Clinical Biochemistry - General

Method and equipment

Equipment : Roche Cobas Pro c503

Method : Homocysteine Enzymatic Assay is based on a novel enzyme cycling assay principle that assesses the co‑substrate conversion product instead of
assessing co‑substrate or Hcy conversion products. In this assay, oxidized Hcy is first reduced to free Hcy which then reacts with a co‑substrate, S‑adenosylmethionine (SAM), to form methionine (Met) and S‑adenosylhomocysteine (SAH), catalyzed by a Hcy S‑methyltransferase.
SAH is assessed by coupled enzyme reactions where SAH is hydrolyzed into adenosine (Ado) and Hcy by SAH hydrolase, and Hcy is cycled into the
Hcy conversion reaction to form a reaction cycle that amplifies the detection signal. The formed Ado is immediately hydrolyzed into inosine and ammonia. In the last step, the enzyme glutamate dehydrogenase (GLDH) catalyzes the reaction of ammonia with 2‑oxoglutarate and NADH to form NAD+ . The concentration of Hcy in the sample is directly proportional to the amount of NADH converted to NAD+ (ΔA340 nm).

Expected turn-around time

STAT/ Urgent/ Routine: 7 Days

Specimen type

Serum, Lithium Heparin / K-EDTA plasma

Specimen requirements

300 uL

Storage and transportation

Frozen

Shipping information

The Hospital for Sick Children

Rapid Response Laboratory

555 University Avenue, Room 3642

Toronto, ON

Canada

M5G 1X8

Phone: 416-813-7200

Toll Free: 1-855-381-3212

Hours: 7 days/week, 24 hours/day

Requisition

Homocysteine, plasma or serum - requisition

Background and clinical significance

Homocysteine (HCY) is a thiol-containing amino acid produced by the intracellular demethylation of methionine. Homocysteine accumulates and is excreted into the blood when these reactions are impaired. Impaired homocysteine metabolism results in hyperhomocysteinemia (increased levels of homocysteine in plasma or serum) or homocystinuria (high plasma levels cause homocysteine to be excreted in urine). Hyperhomocysteinemia is caused by nutritional and genetic deficiencies. The majority of elevated homocysteine cases (two-thirds) in the general population are due to deficiency of folic acid, vitamin B6 and vitamin B12. Severely elevated concentrations of total homocysteine are found in subjects with homocystinuria, a rare genetic disorder of the enzymes involved in the metabolism of homocysteine. Studies have investigated the relationship between elevated homocysteine concentrations and cardiovascular disease (CVD), indicating homocysteine as an important marker for risk assessment