Specimen:

Plasma

Collection Medium:

Alternate
Collection Media:

Call laboratory for additional acceptable specimen collection 
containers.

Minimum:

Adults - 2 mls whole blood in a light green top tube.
Pediatrics - (2) 0.6 ml heparin microtainers (Lithium or Sodium)

Testing
Schedule:

24 hrs/day, 7 days a week, including holidays.

Analytic Time:

1 hour (upon receipt in laboratory)

Reference Range:

< 10 umol/l

Patients with end stage renal disease may have elevated levels of 
cystathionine which may cause a significant positive interference in 
the homocysteine assay.

Test
Limitations:

Homocysteine plasma levels are dependent on B-Vitamin status. The AHA 
target for those with cardiovascular or other risks is < 10 micromol/L. 
(Circulation 1999;99:178-182.)

Cystathionine is measured with homocysteine, but in the general 
population the cystathionine level (0.065 to 0.03 umol/l) has a 
negligible effect.  In very rare, end stage renal disease patients with 
severe metabolic disturbances, cystathionine levels may rise 
dramatically and cause greater than 20% interference.  Refer to the 
SPECIFICITY section of the package insert for cross-reactivity data of 
this drug.  Drugs, such as methotrexate, carbamazepine, phenytoin, 
nitrous oxide, or 6-azauridine triacetate may affect plasma 
concentration of homocysteine.  The mechanism of action affects 
different parts of the metabolic pathway of homocysteine.  Serum 
concentrations can be up to 10% higher than EDTA plasma concentrations.

Sample
Processing:

Centrifuge immediately after drawing specimen.
Centrifuge at 3000 RPM for 10 minutes.
Aliquot serum/plasma into screw-capped plastic vial.

Sample
Storage:

Refrigerate up to 2 days or freeze.

Transport
Instructions:

Place requisition into outside pocket of bag.
Place specimen into zip-lock type bag, seal bag.
Place dry ice on top of specimen in styrofoam container.
Dry Ice up to 24 hours.

Instructions:

Centrifuge and refrigerated, stable for 48 hours at 2-8 degrees C.
Centrifuge and aliquot to plastic tube and freeze.  Stable frozen for 
seven days.