CurrentPremera BluecrossPolicy 15.01.049

Testing of Homocysteine Metabolism-Related Conditions

Defines reimbursement coverage for newborn screening and diagnostic testing related to homocysteine metabolism (including classic homocystinuria/CBS deficiency), specimen types, repeat specimens, pyridoxine challenge test, and tHcy testing in adults; excludes plasma free homocysteine testing. Applies to routine test management (not Medicare Advantage).

Policy Summary

PayerPremera Bluecross

PolicyTesting of Homocysteine Metabolism-Related Conditions

Policy CodePolicy 15.01.049

Change TypeNew policy + coding update

Effective DateFeb 6, 2026

Next Review Date

Key ActionMeasure plasma total homocysteine (tHcy) for diagnosis of suspected homocystinuria and collect/process plasma (centrifuge within an hour and refrigerate or freeze) as recommended by guidelines.

SourceLink

POLICY UPDATE CHANGES

New policy approved October 14, 2025; effective for dates of service on or after February 6, 2026 following 90-day provider notification.

Coding update on 02/06/26 removed CPT codes 82136, 82139, 83921.

1Primary covered CPT code for homocysteine testing

3Reimbursable newborn screening specimen/test types

1Explicitly excluded test (plasma free homocysteine)

2026-02-06

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Coverage Summary

This policy (Policy No. 15.01.049, effective 2026-02-06) defines reimbursement coverage for testing related to homocysteine metabolism and classic homocystinuria (primarily CBS deficiency). The primary covered test for homocysteine is CPT 83090 (homocysteine).

Newborn screening and related testing are explicitly addressed and reimbursable when criteria are met, including quantitative plasma amino acid analysis, plasma or urine total homocysteine (tHcy) analysis, and dried blood spot screening and repeat dried blood specimens. The policy explicitly excludes reimbursement for plasma free homocysteine testing.

Key thresholds & quick facts

Effective date2026-02-06

Primary covered CPT count1 (CPT 83090)

Reimbursable newborn specimen/test types3 (plasma quantitative amino acids, plasma or urine total homocysteine, dried blood spot screening)

Explicitly excluded testPlasma free homocysteine

Normal total homocysteine (tHcy) control threshold<15 µmol/L

Neonate expected tHcy with homocystinuria50 to >100 µmol/L

Untreated older individual expected tHcy>100 µmol/L

Medical-Necessity / Reimbursable Indications

Reimbursable Indications

Testing is considered reimbursable in the following situations:

ANY of the following

Newborn screening for classic homocystinuria due to CBS deficiency by performing quantitative plasma amino acids analysis and/or plasma or urine total homocysteine analysis.
Screening for homocystinuria in dried blood spots.
Screening for hypermethioninemia in dried blood spots.

Related reimbursable actions

Repeated dried blood specimen submitted to the newborn screening program is reimbursable.

Provider Actions and Billing Rules

Documentation Required

Use plasma total homocysteine as frontline test

Measure plasma total homocysteine (tHcy) as the frontline diagnostic test for suspected homocystinuria (CBS deficiency). Collect plasma and process promptly: centrifuge the blood sample within an hour of collection and keep the plasma refrigerated (4°C) or frozen until analysis. CPT code for homocysteine testing: 83090.

Centrifuge plasma within an hour of collection.
Refrigerate (4°C) or freeze plasma until analysis.
Relevant CPT code: 83090.

Prior Authorization

Newborn screening reimbursement process

Submission of newborn dried blood spot specimens and repeat dried blood specimens to the newborn screening program is reimbursable when the policy criteria are met. Reimbursable newborn screening specimen/test types include: dried blood spot screening for homocystinuria and hypermethioninemia, and use of tHcy or plasma amino acid analysis as indicated (including second-tier tHcy on dried blood spots or quantitative plasma amino acids).

Coding

Covered CPT codes (explicitly listed)CPTCovered

83090

Homocysteine

Removed/Updated CPT codes (history)CPT

82136	Removed (historical) - previously listed
82139	Removed (historical) - previously listed
83921	Removed (historical) - previously listed

Background and Evidence

This policy summarizes the clinical rationale for measuring plasma total homocysteine (tHcy) and plasma amino acid analysis to diagnose homocystinuria (primarily CBS deficiency). Classic homocystinuria produces marked elevations of tHcy and methionine, and early detection via newborn screening can prevent severe complications of the disorder.

It references major guideline sources: the HHS Recommended Uniform Screening Panel (which lists homocystinuria as a core newborn screening condition), ACMG guidance recommending quantitative plasma amino acids and plasma Hcy analysis for confirming classic homocystinuria, and E-HOD guidelines that endorse tHcy as the frontline test and recommend using tHcy as a second-tier marker in newborn screening algorithms.

Analytical methods cited include LC-MS (liquid chromatography–mass spectrometry), GC-MS, HPLC, UPLC-MS/MS and FPIA; method validation studies are summarized — for example, LC-MS detection and quantification limits (0.06 µmol/L and 0.6 µmol/L) and GC-MS performance characteristics — supporting reliable measurement of tHcy in plasma and dried blood spots.

Validation studies and newborn screening performance data are noted: dried blood spot two-tier strategies using Met/Phe ratio with second-tier Hcy measurement achieved high sensitivity/specificity in large neonatal cohorts, and comparative studies show good correlation between plasma and dried blood spot tHcy assays for screening and diagnostic use.

E-HOD and ACMG guidance additionally emphasize pre-analytic handling (centrifuge within an hour and refrigerate/freeze) and strongly recommend measuring total homocysteine rather than free homocysteine for diagnosis and screening.

Evidence summary

Revision History

October 14, 2025policy_approval

New policy approved adding newborn screening and related testing for homocysteine-related conditions to the Routine Test Management policy section; specifies reimbursable specimen types and tests and excludes plasma free homocysteine.

February 6, 2026effective_dateLatest

Policy effective for dates of service on or after February 6, 2026 following 90-day provider notification; reimbursable newborn screening, repeat specimens, pyridoxine challenge, specified plasma/urine/dried blood spot analyses, and total plasma homocysteine testing for adults; plasma free homocysteine not reimbursable.

Policy Summary

PayerPremera Bluecross

PolicyTesting of Homocysteine Metabolism-Related Conditions

Policy CodePolicy 15.01.049

Change TypeNew policy + coding update

Effective DateFeb 6, 2026

Next Review Date

SourceLink

On This Page

A quantitative plasma amino acid analysis and analysis of plasma total homocysteine is reimbursable (as repeat/confirmatory testing).

Diagnostic and monitoring in older individuals

Pyridoxine (B6) challenge test is reimbursable for diagnosis of phenotype variants of classic homocystinuria due to CBS deficiency.
For individuals over 18 years with homocystinuria suspected to be caused by CBS deficiency, total homocysteine testing in plasma is reimbursable for diagnosis and for monitoring therapy in confirmed CBS deficiency.

Not Reimbursable

Plasma free homocysteine testing is not reimbursable.

Dried blood spot screening for homocystinuria
Dried blood spot screening for hypermethioninemia
Second-tier tHcy measurement (dried blood spot or plasma) and quantitative plasma amino acid analysis

Documentation Required

Pyridoxine challenge test for phenotype determination

When using a pyridoxine (vitamin B6) challenge to determine the B6‑responsive versus nonresponsive phenotype of CBS deficiency, document the use and results of the B6 challenge in the medical record. The pyridoxine challenge test is considered reimbursable for diagnosis of phenotype variants of classic homocystinuria due to CBS deficiency.

Document administration of pyridoxine challenge and biochemical response (tHcy and Met as appropriate).
Pyridoxine (B6) challenge is reimbursable for phenotype determination.

Billing Rule

Do not bill for plasma free homocysteine

Plasma free homocysteine testing is explicitly excluded from reimbursement and should not be billed as a covered service. Measuring free homocysteine instead of total homocysteine is not recommended by guidelines and carries a high risk of denial if submitted for coverage.

Do not order or bill plasma free homocysteine as a substitute for total homocysteine.
Expect claim denial if plasma free homocysteine is submitted as a covered test.

Recommend quantitative plasma amino acids and plasma total homocysteine analysis to diagnose classic homocystinuria

E-HOD recommendationStrong recommendation to measure plasma total homocysteine as frontline test and to not measure free homocysteine instead of total

Analytical validity (LC-MS) - Nelson et al. 2003LC-MS limit of detection 0.06 µmol/L; limit of quantification 0.6 µmol/L

E-HOD newborn screening guidanceUse elevated Met and/or Met/Phe ratio with tHcy as second-tier to increase specificity

E-HOD monitoring/targetsProposed target tHcy <50 µmol/L in pyridoxine-responsive; free Hcy <11 µmol/L (~120 µmol/L total) in pyridoxine-unresponsive

Definitions

tHcyTotal homocysteine measured in plasma; primary clinical analyte for diagnosing homocystinuria

CBSCystathionine β-synthase; enzyme whose deficiency causes classic homocystinuria

CPT code set updated: removed CPT codes 82136, 82139, and 83921; CPT 83090 remains listed for homocysteine.