Homocysteine Testing

This policy covers homocysteine testing for diagnosis and monitoring of disorders of sulfur‑bearing amino‑acid metabolism (including homocystinuria due to cystathionine β‑synthase deficiency), for use with methylmalonic acid (MMA) to help diagnose established vitamin B12 deficiency, and for screening/treatment consideration in memory‑clinic patients per consensus guidance. It specifies that homocysteine testing alone has limited utility—generally should be interpreted with concurrent MMA—and is not supported as improving outcomes for cardiovascular risk assessment, venous thromboembolism, or dementia prevention (considered investigational for borderline/inconclusive B12 results and idiopathic VTE), with no established homocysteine threshold to guide intervention.

"Homocysteine testing is medically necessary for homocystinuria caused by cystathionine beta-synthase deficiency."