ICD-9 Code for Homocysteine Testing
There is no specific ICD-9 code for ordering a homocysteine test itself, as ICD-9 codes are diagnosis codes, not procedure codes. However, you need to use an appropriate diagnosis code that justifies the medical necessity for checking homocysteine levels.
Relevant ICD-9 Diagnosis Codes to Justify Homocysteine Testing
For patients with cardiovascular disease or kidney disease, the following ICD-9 codes can be used to justify ordering homocysteine levels:
Cardiovascular Disease-Related Codes
- History of stroke or TIA: Use codes for cerebrovascular disease to justify testing, as hyperhomocysteinemia is associated with a 2-3 fold increased risk of atherosclerotic vascular disease 1
- Coronary artery disease: Relevant codes can justify testing, as an increment of 5 μmol/L in homocysteine confers equivalent CAD risk to a 20 mg/dL increase in plasma cholesterol 2
Kidney Disease-Related Codes
- 585.1 - CKD Stage 1 (kidney damage with normal or increased GFR) 1
- 585.2 - CKD Stage 2 (kidney damage with mild decreased GFR) 1
- 585.3 - CKD Stage 3 (moderate decreased GFR, chronic renal insufficiency) 1
- 585.4 - CKD Stage 4 (severe decreased GFR, late renal insufficiency, pre-ESRD) 1
- 585.5,585.6 - CKD Stage 5 (kidney failure, uremia, ESRD) 1
Clinical Context for Testing
Homocysteine testing is clinically justified in older adults with cardiovascular or kidney disease because:
- Hyperhomocysteinemia has a prevalence of 85-100% in hemodialysis patients 2
- Decreased renal clearance of homocysteine in CKD patients leads to elevated levels 2
- For every 5 μmol/L increase in homocysteine, stroke risk increases by 59% 2, 3
- Plasma homocysteine is a strong independent mortality predictor in hemodialysis patients, with a 3% increase in mortality for each 1 μmol/L increase 4
Important Clinical Considerations
When ordering homocysteine testing, the Fabry disease management guidelines recommend checking "total plasma homocysteine" as part of neurologic comorbid stroke risk factor assessment at baseline as a single assessment 1. This should be obtained as a fasting plasma homocysteine level after at least 8 hours of fasting 2.
The American College of Medical Genetics emphasizes that plasma homocysteine measurement is more informative than molecular MTHFR testing alone, as homozygosity for MTHFR mutations accounts for only about one-third of hyperhomocysteinemia cases 2.