Aetna modified CPB 0351 covering flow cytometry, ektacytometry, DNA ploidy, and S-phase fraction testing, effective February 27, 2026. Here's what billing teams need to do.
Aetna, a CVS Health company, updated CPB 0351 to clarify medical necessity criteria and coverage boundaries for a broad set of diagnostic tests. The policy covers CPT codes 88182, 88184, 88185, 88187, 88188, 88189, and 86360, among others. Several sickle cell and RBC adhesion codes — including 0121U, 0122U, 0303U, and 0304U — are explicitly excluded. If your lab, hematology, oncology, or pathology billing team bills any of these codes to Aetna, this coverage policy update deserves your attention now.
Quick-Reference Table
| Field | Detail |
|---|---|
| Payer | Aetna, a CVS Health company |
| Policy | Flow Cytometry, Ektacytometry, DNA Ploidy, and S-Phase Fraction |
| Policy Code | CPB 0351 |
| Change Type | Modified |
| Effective Date | February 27, 2026 |
| Impact Level | High |
| Specialties Affected | Hematology, Oncology, Pathology, Immunology, Transplant Medicine, Infectious Disease |
| Key Action | Audit active claims for CPT 88182–88189, 86360, and 0305U against updated medical necessity criteria before billing |
Aetna Flow Cytometry Coverage Criteria and Medical Necessity Requirements 2026
The Aetna flow cytometry coverage policy under CPB 0351 covers cell surface marker testing — billed under CPT 88184, 88185, 88187, 88188, and 88189 — for 15 specific indications. Every one of those indications requires that the test be medically necessary. Aetna does not cover flow cytometry as a general workup tool.
The clearest covered use is immunophenotyping for leukemia, lymphoma, or myelodysplastic syndrome. That's the core indication most labs will bill against. But the policy also covers T-cell monitoring for HIV and AIDS (ICD-10 B20), B-cell monitoring for immunosuppressive disorders, and post-operative organ transplant monitoring — all with CPT 86360 for CD4/CD8 ratio work.
A few indications are worth flagging specifically because they're easy to miss. Mast cell disease is covered. Paroxysmal nocturnal hemoglobinuria is covered. Sezary syndrome diagnosis is covered. Primary immunodeficiencies are covered. Each of these requires chart documentation that squarely supports the indication — vague or incomplete documentation is your fastest path to a claim denial.
The CD4/CD8 ratio from bronchiolar lavage fluid for sarcoidosis diagnosis is also covered. That's a narrow, specific indication. If you bill 86360 for sarcoidosis, the source of the specimen matters — it must be bronchiolar lavage, not peripheral blood.
DNA Ploidy and S-Phase Fraction: Covered, But Only Under Tight Conditions
DNA content (ploidy) and cell proliferative activity — S-phase fraction, billed under CPT 88182 — face a higher bar. A National Institutes of Health consensus finding underpins Aetna's position here: these tests are not appropriate for routine cancer management.
Aetna considers DNA ploidy and S-phase fraction medically necessary only for nine specific localized cancers without metastatic disease, and only when the prognostic results will directly affect treatment decisions. That last phrase is doing a lot of work. "Will affect treatment decisions" is not a box to check — it requires physician documentation explaining how the result changes the treatment plan.
The nine covered cancers are endometrial adenocarcinoma, gastric cancer, mediastinal neuroblastoma, medulloblastoma, ovarian carcinoma, partial hydatidiform mole, prostatic adenocarcinoma, renal cell adenocarcinoma, and urinary bladder carcinoma. This test typically runs once per tumor lifetime, after diagnosis and before treatment starts. Billing it multiple times for the same tumor will draw scrutiny.
Ektacytometry: Covered as a Last Resort for RBC Disorders
Ektacytometry — assessed via CPT 0305U — is covered for diagnosing RBC cytoskeleton and hydration disorders. The list includes hereditary spherocytosis, pyro-poikilocytosis, stomatocytosis, ovalocytosis, elliptocytosis, and xerocytosis. The trigger is specific: RBC morphology must not have provided a clear diagnosis first. Ektacytometry is a second-line test under this coverage policy. Bill it as a first-line test and you're looking at a denial.
This is the same logic Aetna applies across several diagnostic categories — the simpler, cheaper test must fail before the more complex one gets covered. Make sure your documentation sequence reflects that order.
Aetna Flow Cytometry Exclusions and Non-Covered Indications
The exclusion list in CPB 0351 is explicit and financially significant.
RBC adhesion index testing — including Hypoxic BioChip Adhesion and Normoxic BioChip Adhesion — is experimental, investigational, and unproven for all indications. CPT codes 0121U, 0122U, 0303U, and 0304U are all explicitly not covered. These are the sickle cell microfluidic adhesion tests. If your practice has been billing these to Aetna, stop and audit your claims back to the effective date of February 27, 2026.
DNA ploidy and S-phase fraction are also excluded for several major cancer types. Breast cancer, cervical cancer, colorectal cancer, and non-small cell lung cancer are all non-covered indications for CPT 88182. These are high-volume cancer diagnoses. The financial exposure here is real — especially for oncology practices that run DNA ploidy panels as part of a broader cancer workup.
CPT 0606U, the osmotic gradient ektacytometry code for red cell membrane disorders, is also not covered under this policy. That's a distinction from CPT 0305U, which covers RBC functionality and deformability. Know which ektacytometry code you're billing — the wrong one gets denied on the first pass.
The policy makes clear this is not an all-inclusive exclusion list. If you're billing a cancer indication not listed among the nine covered types, treat it as non-covered unless you have a specific exception documented.
Coverage Indications at a Glance
| Indication | Status | Relevant CPT Codes | Notes |
|---|---|---|---|
| Leukemia/lymphoma/MDS immunophenotyping | Covered | 88184, 88185, 88187, 88188, 88189 | Standard cell surface marker workup |
| HIV/AIDS T-cell monitoring (ICD-10 B20) | Covered | 86360 | CD4/CD8 ratio, absolute count |
| B-cell monitoring for immunosuppressive disorders | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Organ transplant post-op monitoring | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Paroxysmal nocturnal hemoglobinuria | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Mast cell disease | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Sezary syndrome (diagnosis) | Covered | 88184, 88185, 88187, 88188, 88189 | Diagnosis only |
| Primary immunodeficiencies | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Sarcoidosis (CD4/CD8 from bronchiolar lavage) | Covered | 86360 | Must be bronchiolar lavage specimen |
| Hereditary spherocytosis (Coombs' negative hemolytic anemia) | Covered | 88184, 88185 | — |
| Hereditary persistence of fetal hemoglobin | Covered | 88184, 88185 | Unexplained increase in hemoglobin F |
| Hairy cell monitoring | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Multiple myeloma | Covered | 88184, 88185, 88187, 88188, 88189 | — |
| Myeloproliferative neoplasms (AML transformation workup) | Covered | 88184, 88185, 88187, 88188, 88189 | Disease progression or transformation only |
| DNA ploidy/S-phase: endometrial, gastric, neuroblastoma, medulloblastoma, ovarian, hydatidiform mole, prostate, renal cell, bladder (localized, no mets) | Covered — conditionally | 88182 | Results must affect treatment decisions; typically once per tumor |
| RBC cytoskeleton/hydration disorders (ektacytometry) | Covered — second line | 0305U | Only when RBC morphology is inconclusive |
| Breast cancer — DNA ploidy/S-phase | Not Covered | 88182 | Experimental/investigational per NIH consensus |
| Cervical cancer — DNA ploidy/S-phase | Not Covered | 88182 | Experimental/investigational |
| Colorectal cancer — DNA ploidy/S-phase | Not Covered | 88182 | Experimental/investigational |
| Non-small cell lung cancer — DNA ploidy/S-phase | Not Covered | 88182 | Experimental/investigational |
| RBC adhesion index (all indications) | Not Covered | 0121U, 0122U, 0303U, 0304U | Experimental/investigational for all indications |
| Osmotic gradient ektacytometry (0606U) | Not Covered | 0606U | Not covered per CPB 0351 |
Aetna Flow Cytometry Billing Guidelines and Action Items 2026
| # | Action Item |
|---|---|
| 1 | Audit your CPT 88182 claims immediately. Pull every claim billed to Aetna under CPT 88182 for breast, cervical, colorectal, and non-small cell lung cancer diagnoses. These are now explicitly non-covered under CPB 0351. Claims submitted after February 27, 2026 for these indications will deny. Claims already in the pipeline need review. |
| 2 | Stop billing 0121U, 0122U, 0303U, and 0304U to Aetna. These RBC adhesion codes are excluded under this coverage policy. Aetna will not reimburse them. If your hematology team runs these for sickle cell patients covered by Aetna, you need a billing alternative or a prior authorization pathway before ordering. |
| 3 | Check your ektacytometry code. If you bill ektacytometry to Aetna, confirm you're using 0305U — not 0606U. The osmotic gradient ektacytometry code (0606U) is not covered. Only 0305U for RBC functionality and deformability is covered, and only when RBC morphology was inconclusive. Update your charge capture to flag 0606U for Aetna claims. |
| 4 | Document the treatment decision link for every CPT 88182 claim. For DNA ploidy and S-phase fraction on the nine covered cancer types, the chart must show how the test result will change the treatment plan. A generic order isn't enough. Work with your ordering physicians to make sure the clinical note addresses this directly before you submit. |
| 5 | Verify specimen source for sarcoidosis CD4/CD8 claims. If you bill 86360 with a sarcoidosis diagnosis, Aetna requires the specimen to be bronchiolar lavage fluid — not peripheral blood. If the source isn't documented in the chart, the claim is at risk. |
| 6 | Update your prior authorization workflow. The policy doesn't specify prior auth requirements by code, but flow cytometry panels — especially multi-marker studies (88187, 88188, 88189) and DNA ploidy — carry enough financial weight that you should confirm your Aetna authorization requirements before the test runs. Check your current payer contract and Aetna's prior authorization list for these CPT codes. |
| 7 | Brief your lab billing team on the S-phase frequency rule. CPT 88182 for DNA ploidy should bill once per tumor, after diagnosis and before treatment. If your system allows repeat billing on the same tumor, build a hard stop or an edit rule. |
If your practice is across multiple specialties — particularly oncology, hematology, and pathology — and you're unsure how the nine covered cancer indications map to your current order sets, talk to your compliance officer before the effective date has passed.
| Previous Version | Current Version |
|---|---|
| Coverage is considered experimental and investigational for all indications | Coverage is considered medically necessary when specific criteria are met |
| Prior authorization is not required | Prior authorization is required for initial treatment |
| Documentation must include clinical history | Documentation must include clinical history |
| Re-review every 24 months | Re-review every 12 months with updated clinical documentation |
CPT, HCPCS, and ICD-10 Codes for Flow Cytometry Under CPB 0351
Covered CPT Codes (When Selection Criteria Are Met)
| Code | Type | Description |
|---|---|---|
| 0305U | CPT (PLA) | Hematology, red blood cell (RBC) functionality and deformity as a function of shear stress, whole blood |
| 86360 | CPT | T cells; absolute CD4 and CD8 count, including ratio |
| 88182 | CPT | Flow cytometry, cell cycle or DNA analysis |
| 88184 | CPT | Flow cytometry, cell surface, cytoplasmic, or nuclear marker, technical component only; first marker |
| +88185 | CPT (add-on) | Each additional marker (List separately in addition to code for first marker) |
| 88187 | CPT | Flow cytometry, interpretation; 2 to 8 markers |
| 88188 | CPT | Flow cytometry, interpretation; 9 to 15 markers |
| 88189 | CPT | Flow cytometry, interpretation; 16 or more markers |
Not Covered / Experimental Codes
| Code | Type | Description | Reason |
|---|---|---|---|
| 0121U | CPT (PLA) | Sickle cell disease, microfluidic flow adhesion (VCAM-1), whole blood | Not covered per CPB 0351 |
| 0122U | CPT (PLA) | Sickle cell disease, microfluidic flow adhesion (P-Selectin), whole blood | Not covered per CPB 0351 |
| 0303U | CPT (PLA) | Hematology, red blood cell (RBC) adhesion to endothelial/subendothelial adhesion molecules, functionality | Not covered per CPB 0351 |
| 0304U | CPT (PLA) | Hematology, red blood cell (RBC) adhesion to endothelial/subendothelial adhesion molecules, functionality | Not covered per CPB 0351 |
| 0606U | CPT (PLA) | Hematology (red cell membrane disorders), RBCs, osmotic gradient ektacytometry, whole blood, quantitative | Not covered per CPB 0351 |
Key ICD-10-CM Diagnosis Codes
| Code | Description |
|---|---|
| B20 | Human immunodeficiency virus [HIV] disease — T-cell monitoring |
| C16.0–C16.9 | Malignant neoplasm of stomach — gastric cancer (localized, without metastatic disease) |
| C18.0–C21.8 | Malignant neoplasm of colon, rectosigmoid junction, rectum, anus and anal canal — colorectal cancer (not covered for DNA ploidy) |
| C34.0–C34.9x | Malignant neoplasm of bronchus and lung — non-small cell lung cancer (not covered for DNA ploidy) |
The full ICD-10-CM code list for CPB 0351 includes 329 codes. Review the complete list at app.payerpolicy.org/p/aetna/0351.
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