Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (985 page)

   
Normal range:
5.0–15 μmol/L.

   Use

   Elevated levels of tHcy may be used to exclude or confirm deficiencies of vitamin B
₁₂
or folate.

   It is recommended to test in patients using medications that interfere with folate status (methotrexate, antiepileptics), vegetarians without B
₁₂
supplementation, unexplained anemia, peripheral neuropathy or myleopathy, recurrent spontaneous abortions or infertility.

   Testing also recommended for patients 40 years of age with coronary artery disease to exclude homocystinuria.

   Elevations in tHcy levels have also been used as an independent risk factor of coronary or cerebral vascular disease. Treatment of moderate hyperhomocystinemia with folic acid supplementation for primary and secondary cardiovascular protection has met with inconsistent results and at present cannot be routinely recommended.

   Interpretation

   Hyperhomocystinemia has been classified as follows:

   Moderate: 15–30 μmol/L

   Intermediate: 30–100 μmol/L

   Severe: >100 μmol/L

Increased In

   Vitamin B
₁₂
, vitamin B
₆
, or folate deficiency

   Hypothyroidism