CPT code 82784 – Immunoglobulin IgA, IgD, IgG, IgM billing guide

Key takeaways

CPT code 82784 covers quantitative IgA, IgD, IgG, and IgM testing, while IgE is reported under CPT 82785.

Each immunoglobulin class counts as one unit, so an IgA, IgG, and IgM panel bills three units of 82784.

Medicare prices 82784 on the Clinical Laboratory Fee Schedule at about $9.30 per unit, with no locality adjustment.

An ICD-10-CM code from the D80-D89 range, or another covered indication, must support medical necessity on every claim.

Practice management software like Pabau links lab orders to claims and flags missing ICD-10 codes before submission.

CPT code 82784: official description and clinical overview

CPT code 82784 describes the quantitative measurement of gammaglobulin (immunoglobulin), including IgA, IgD, IgG, or IgM, each. The test runs on a serum specimen. The word “each” in the descriptor carries the billing rule. Every immunoglobulin class ordered is counted and reported as a separate unit.

The code belongs to the Chemistry Procedures subsection within the Pathology and Laboratory section of the CPT code set, maintained by the American Medical Association. Two neighboring codes are the ones coders reach for by mistake. CPT 82785 reports IgE, and CPT 82787 reports immunoglobulin subclasses. Neither one is interchangeable with 82784.

The four immunoglobulin classes covered by this code have distinct clinical roles:

• IgG: The most abundant serum immunoglobulin; elevated in chronic infections, autoimmune disease, and multiple myeloma.
• IgA: Found in mucosal secretions; deficiency is common in selective IgA deficiency, celiac disease, and certain autoimmune conditions.
• IgM: The primary antibody in acute infection responses; elevated levels can indicate Waldenstrom macroglobulinemia or early immune activation.
• IgD: Least frequently ordered; useful in evaluating IgD myeloma and certain inherited immunodeficiency workups.

Clinical indications for quantitative immunoglobulin testing

Physicians order the test to evaluate immune function, or to work up a condition involving too little or too much immunoglobulin. The indication decides which diagnosis code goes on the claim. Pairing the two at the point of order is what protects the payment later.

Common clinical indications include:

• Recurrent or unusual infections (suspected primary or secondary immunodeficiency)
• Evaluation of hypogammaglobulinemia or agammaglobulinemia
• Monitoring known immunodeficiency disorders (common variable immunodeficiency, selective IgA deficiency)
• Workup for suspected multiple myeloma or Waldenstrom macroglobulinemia
• Post-treatment monitoring after immunosuppressive therapy or stem cell transplant
• Celiac disease evaluation (IgA deficiency affects tTG-IgA test validity)
• Assessment of autoimmune conditions where immunoglobulin levels guide treatment decisions

The test is not appropriate as a routine screening tool without a clinical indication. Payers, including Medicare Administrative Contractors (MACs), will deny claims where medical necessity is not clearly documented in the patient’s record.

ICD-10-CM codes that support medical necessity for 82784

Every CPT 82784 claim needs an ICD-10-CM diagnosis code that justifies the test. Covered indications are set by each Medicare Administrative Contractor (MAC) in its own local coverage determination. Check the active LCD for your jurisdiction in the CMS Medicare Coverage Database. The D80-D89 chapter, disorders involving the immune mechanism, holds the codes paired with this test most often.

Covered code lists differ between MAC regions, so a diagnosis one contractor accepts may need extra documentation under another. Our ICD-10-CM code library carries the full official descriptor behind each of the codes above. Confirm the patient’s coverage before the specimen is drawn, rather than after the claim comes back denied.

Medicare reimbursement for 82784 under the lab fee schedule

Medicare pays CPT code 82784 from the Clinical Laboratory Fee Schedule (CLFS), not from the physician fee schedule. The CMS Clinical Laboratory Fee Schedule file is the authoritative source for the amount. For 2026 the code pays roughly $9.30 per unit.

That figure is one flat national rate. There is no facility versus non-facility split, no RVU calculation, and no geographic adjustment by MAC region. An RVU lookup is the wrong instrument for a clinical chemistry code. Never use a figure it returns to check a lab payment.

Because the rate is per unit, the size of the panel decides the payment. The chart below runs the arithmetic for the combinations ordered most often.

Clinical diagnostic laboratory tests are also paid on an assignment-related basis. Medicare pays 100% of the schedule amount, and neither the Part B deductible nor the 20% coinsurance applies. No balance is left to bill the patient, so a unit count that comes in low is revenue the practice never recovers.

How Medicare sets the 82784 rate

CLFS amounts are built from the private-payer rates laboratories report to CMS under the Protecting Access to Medicare Act (PAMA). CMS takes the weighted median of those reported rates and publishes it as the national payment amount for the code. Updated files are posted on the CMS CLFS page, so pull the current one instead of carrying last year’s figure forward.

Because 82784 is a laboratory chemistry code, the specimen usually goes to an independent or reference laboratory. That laboratory bills the code under its own NPI, and the ordering physician does not bill it at all. The rate matters most to practices running immunoglobulin testing in house.

Billing guidelines and the “each” unit rule

The unit structure in the official descriptor decides whether this code is billed correctly. A practice that reports 82784 as a single unit, whatever the panel size, under-bills every immunology order it sends out. The unit count belongs in the order workflow, not in a correction at claim submission.

Billing multiple immunoglobulin classes on the same date of service

A physician who orders IgA, IgG, and IgM on one date of service generates three units. Report CPT 82784 with three units, one per class. Some practice management systems default to a unit of 1 regardless of how many classes are ordered, which creates systematic under-reimbursement on every immunology panel.

• IgA ordered: 82784 x 1 unit
• IgG ordered: 82784 x 1 unit (in addition to IgA)
• IgM ordered: 82784 x 1 unit (in addition to IgA and IgG)
• IgA + IgG + IgM ordered together: 82784 x 3 units on the same claim line, or three separate line items
• IgD ordered: 82784 x 1 additional unit

Some payers require separate line items rather than a single line with multiple units. Check payer-specific billing manuals before submission. Modifier 59 (distinct procedural service) may be appropriate when payer edits flag multiple units of one code. Apply it only where the services are genuinely distinct. Verify applicable modifier rules with the specific MAC or commercial payer.

Documentation requirements to support 82784 claims

After incorrect units, thin documentation is the next most common reason an 82784 claim is denied. Medicare expects a clear trail from the clinical indication through to the ordered specimen. The diagnosis code on the claim has to be supported by what is written in the chart.

Required documentation elements:

• Physician order: A signed order specifying which immunoglobulin class(es) are being measured. Verbal or standing orders require supporting documentation of clinical indication.
• Clinical indication: The patient’s record must contain a documented clinical reason for the test (e.g., recurrent sinopulmonary infections, suspected CVID, monitoring post-transplant immune reconstitution).
• ICD-10-CM linkage: The diagnosis code on the claim must be supported by the documentation in the patient’s chart, not just entered on the claim form.
• Specimen type: Serum is the standard specimen for CPT 82784. If a non-standard specimen is used, document the clinical reason.
• Test frequency: If ordering the test more frequently than typical (e.g., monthly for CVID monitoring), document the clinical rationale in the chart.

Verifying benefits before the encounter also shows whether the plan requires prior authorization for immunoglobulin panels, which some commercial payers do. A missed prior authorization cannot be recovered on appeal.

Related CPT codes and when to use them instead of 82784

Picking the wrong code from the immunoglobulin and serum protein family is a steady source of rejections. The table below sets out the neighbors of 82784 and the clinical question each one answers.

82784 vs 82785: key differences

CPT 82785 covers IgE only, while CPT 82784 covers IgA, IgD, IgG, and IgM. The clinical contexts do not overlap: 82785 supports allergy and atopy workups, whereas 82784 supports immune deficiency, autoimmune disease, and plasma cell disorder evaluation. Reporting 82785 when IgE is ordered alongside an IgG/IgA/IgM panel requires both codes on the same claim, each with one unit. Using 82784 to report IgE is incorrect and will be denied on audit.

Common claim denial reasons for 82784

Denials on this code cluster around four root causes, and each one is preventable at the point of order rather than at appeal. A working denial management process for lab codes lets billing teams build upstream edits instead of chasing reversals.

• Missing or unsupported ICD-10-CM code: The most common denial. The diagnosis code on the claim must be present in the patient’s documentation. A claim where D83.9 is billed but the chart contains no reference to immunodeficiency fails on medical necessity review. Link every order to a documented clinical indication before billing.
• Incorrect unit count: Billing one unit when three classes were tested underpays the practice. Billing three units when only one class was ordered triggers fraud and abuse scrutiny. The unit count must match what was ordered and performed.
• Missing physician order: Reference laboratories require a signed order. If the ordering provider’s NPI cannot be linked to a documented order, payers reject on insufficient documentation. Maintain a copy of the requisition in the patient’s record.
• Unbundling errors with panel codes: A laboratory panel code may already include IgG, IgA, or IgM. Billed alongside 82784, it can make the payer flag the individual units as redundant. Check whether the panel code subsumes the individual Ig measurements before billing both.

Building an 82784 audit into the monthly billing review keeps the same denials from recurring. Sort denied claims by reason code, find the cause upstream, and fix the workflow rather than appealing each claim on its own.

How claims management software protects 82784 reimbursement

The errors above share one cause. Lab orders, clinical notes, and claim submission sit in separate systems. A practice that orders labs in its EHR, documents in another platform, and bills through a standalone clearinghouse has three handoffs. The class count, the diagnosis link, or the signed order can fall out of step at any one of them.

Practice management software like Pabau keeps the order, the note, and the claim on one patient record. Pabau’s connected claims management software carries each immunoglobulin class ordered onto the claim as its own line. The biller sees the unit count before the claim is released. Diagnosis codes recorded against the visit are carried through to the claim form, which removes a manual re-entry step. Your coding team still decides which codes belong on the claim.

For electronic submission, Pabau connects to Claim.MD, our US clearinghouse partner, which reaches thousands of US payers. The integration supports CMS-1500 and 837P claims, eligibility checks, and electronic remittance advice. Denial reason codes come back into the same workflow as the original claim. Seeing them there is what makes it practical to act on a pattern.

Practices running immunoglobulin testing in house can track specimen collection, result receipt, and billing status inside that same record. When the requisition, the result, and the claim sit together, a missing-order denial has an answer attached to it rather than a paper chase.

Keep lab orders, notes, and claims on one record

Pabau holds the lab order, the clinical note, and the claim in a single patient record. Your team can check 82784 unit counts and diagnosis links before the claim goes out.

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Conclusion

Most of what goes wrong with this code is settled before the claim is built. The unit count follows the order, the diagnosis link follows the chart, and the signed requisition either exists or it does not. A billing team that inherits those three things clean has very little left to get wrong.

Start with an audit of last quarter’s 82784 claims against the orders behind them. Single units billed against multi-class panels show what the current workflow costs. That figure usually justifies fixing the order step rather than the claim step. Book a demo to see how Pabau keeps lab orders, notes, and claims on one record.

Continue your research

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Dealing with repeated lab claim rejections? Denial management in healthcare covers how to build a systematic response to payer rejections across code types.

Looking for clearinghouse options for electronic claim submission? Claim.MD clearinghouse overview explains how the integration works for US practices billing Medicare and commercial payers.

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