83520 CPT Code

83520 CPT Code Reimbursement Explained

CPT code 83520 is an important medical code that is used for immunoassay testing. Here are some key takeaways about cpt code 83520:

  • CPT code 83520 refers to quantitative immunoassay testing for substances in the body other than antibodies or antigens.
  • It is part of the CPT category of immunoassay testing codes and is considered aTier 2 stacked code.
  • CPT 83520 may be used to bill for quantitative tests that measure things like hormones, vitamins, therapeutic drugs, and more.
  • The code does not cover infectious disease antibody or antigen testing. Other CPT codes like 86318 or 86704 would be used instead.
  • Medicare reimburses around $45 for CPT 83520 when billed with appropriate diagnosise codes. Coverage and reimbursement varies by payer.

Full Description of CPT Code 83520

CPT code 83520 stands for:

Immunoassay for analyte other than infectious agent antibody or infectious agent antigen; quantitative, not otherwise specified

It is part of the tier 2 stacked CPT code set for immunoassays and refers specifically to quantitative immunoassays.

Some key notes on 83520:

  • It can be used to bill for quantitative lab tests that measure a wide variety of substances like hormones, vitamins, therapeutic drugs, and more.
  • The analyte measured must be something other than an infectious agent antibody or antigen. seperate CPT codes exist for infectious disease testing.
  • The test must be quantitative in nature, measuring specific concentrations or amounts. Qualitative “yes/no” tests are not billed under 83520.
  • The test methodology must be an immunoassay technique like ELISA, EIA, or others.

Appropriate Use of CPT Code 83520

Some examples of appropriate use of CPT code 83520 include:

  • Quantitative measurement of steroid hormones like estradiol, testosterone, or progesterone
  • Therapeutic drug monitoring to measure blood levels of medications
  • Vitamin D quantification
  • Quantitative thyroid hormone tests like T3, T4, or TSH
  • Measuring concentrations of cardiac markers like troponin or CK-MB

CPT 83520 should not be used for:

  • Qualitative “yes/no” immunoassay tests
  • Infectious disease antibody or antigen tests like HIV, hepatitis, or Lyme disease
  • Non-immunoassay quantitative lab tests like mass spectrometry

Billing and Reimbursement for 83520

CPT code 83520 is often billed by clinical laboratories when performing medically appropriate quantitative immunoassays.

Some key billing notes:

  • The appropriate ICD-10 diagnosis code(s) must be included to indicate medical necessity
  • Most payers including Medicare require prior authorization for some quantitative immunoassays
  • Medicare reimburses around $45 for CPT 83520 nationally, though local coverage may vary
  • Private insurers reimbursement varies, though often ranges between $30-60
  • Patients may be responsible for coinsurance, copays, or deductibles as set by their insurance

Labs should always check payer policies and acquire prior authorization if needed before performing immunoassay tests to avoid denial of claims.

When CPT Code 83520 is Used

CPT code 83520 may be used any time a medically necessary quantitative immunoassay is performed to measure an analyte other than infectious disease antibodies/antigens.

Some examples of when 83520 may be used:

  • Monitoring blood levels of medications like gentamicin, lithium, or anti-seizure drugs
  • Evaluating thyroid function in patients with suspected hyper/hypothyroidism
  • Assessing fertility and ovarian reserve in women struggling to conceive
  • Checking vitamin D levels in patients at risk for deficiency
  • Quantifying cardiac markers like troponin after a heart attack

The decision to use CPT code 83520 is made by the ordering provider to help diagnose or manage a patient’s condition when a quantitative immunoassay test is appropriate. It should only be used when the test is medically necessary.


  • CPT 83520 allows labs to bill for quantitative immunoassays measuring non-infectious disease analytes
  • It covers testing for hormones, vitamins, medications, cardiac markers, and more
  • Labs must verify payer coverage criteria are met before performing tests billed under 83520
  • Billing requires an appropriate ICD-10 code to reflect medical necessity
  • Medicare reimburses around $45 nationally for 83520, but coverage varies by payer

Use of CPT code 83520 should be limited to medically appropriate, quantitative immunoassay testing to ensure proper reimbursement and coverage. Clinical labs should always clarify payer policies before performing immunoassay tests.

shahid maqsood

Shahid Maqsood is an experienced writer and journalist with 10+ years in the industry. He is Content writer and Editor , where he writes daily articles covering topics like books, business, news, sports, and more. Shahid holds an MBA from Virtual University of Pakistan and a Master’s in Mass Communications. He is based in Faisalabad, Pakistan.

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