1. Immediately place specimen on wet ice.
2. Spin down and separate plasma from cells within 4 hours of draw. A refrigerated centrifuge is not required if 4-hour time restraint is met.
3. Alternatively, if blood is not immediately placed on ice, plasma must be removed from cells within 1 hour of draw. A refrigerated centrifuge is not required if 1-hour time restraint is met.
Homocysteine concentrations >13 mcmol/ L are considered abnormal in patients evaluated for suspected nutritional deficiencies (B12, folate) and inborn errors of metabolism. Measurement of methylmalonic acid (MMA) distinguishes between B12 (cobalamin) and folate deficiencies, as MMA is only elevated in B12 deficiency. Response to dietary treatment can be evaluated by monitoring plasma homocysteine concentrations over time.
Homocysteine concentrations< or =10 mcmol/L are desirable when utilized for cardiovascular risk.