Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (986 page)

   Chronic renal failure

   Coronary heart disease

Decreased In

   Down syndrome

   Pregnancy

   Hyperthyroidism

   Early diabetes

   Limitations

   The plasma (or serum) must be separated immediately on collection to avoid continuous synthesis of Hcy by red cells.

   Samples must be immediately stored on ice and serum centrifuged immediately, before a complete clot is formed, to prevent erroneous results due to the presence of fibrin.

   Certain drugs, such as anticonvulsants, methotrexate, or nitrous oxide, may interfere with the assay.

   Cigarette smoking and coffee consumption increase tHcy levels.

   Intraindividual variability is approximately 8%; it can be as much as 25% in patients with hyperhomocystinemia.

   Generally, a single measurement of tHcy is considered adequate.

Suggested Readings

Clarke R, Daly L, Robinson K, et al. Hyperhomocysteinemia: An independent risk factor for vascular disease.
N Engl J Med.
1991;324:1149–1155.