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    OpenPayerBilling CodesDiagnostic Nuclear Medicine Procedures on the Hematopoietic, Reticuloendothelial and Lymphatic SystemCPT cpt-78121-red-cell-volume-multiple-sample-method
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    CPT 78121: Red Cell Volume by Multiple-Sample Radioisotope Method

    Medicare pays $68 on average nationally for this procedure.

    CPT code 78121 describes a red cell volume measurement using a multiple-sample radioisotope technique in which a known quantity of radiolabeled red blood cells is introduced and serial samples are measured after adequate mixing; this diagnostic nuclear medicine blood volume study is typically performed as an outpatient procedure or in a hospital imaging or nuclear medicine department to quantify circulating red blood cell volume.

    For related coverage guidance, see recent payer policy updates: Vafseo (vadadustat) for anemia in CKD on dialysis, Metabolic Disorders - Cysteamine (Oral) Products for Individual and Family Plans, Kerendia (finerenone) — Coverage Criteria.

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    Clinical & Coding Specifications

    Clinical Context

    A typical patient is a 65-year-old male referred by a hematologist for measurement of red cell volume (RCV) to evaluate unexplained anemia and to quantify blood loss or red cell mass in cases of suspected polycythemia or hemodilution. The patient arrives at an outpatient nuclear medicine or hospital clinical laboratory. After informed consent, a technologist or nuclear medicine nurse establishes venous access and withdraws baseline blood samples. A known quantity of autologous or homologous red blood cells labeled with a radioactive tracer (commonly chromium-51 or similar) is injected. Multiple timed blood samples are drawn over an interval to allow adequate mixing and equilibration. A laboratory technologist measures radioactivity in the samples to calculate the circulating red cell volume using established decay and dilution equations. The interpreting physician (nuclear medicine physician, hematologist, or pathologist) reviews results, documents the quantitative RCV and interpretation, and communicates findings to the referring clinician for management decisions such as transfusion planning, phlebotomy, or further diagnostic workup.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    36415Collection of venous blood by venipunctureVenous blood draws required before and after tracer injection for radioassay sampling.
    78295Myocardial imaging, planar and/or SPECT, multiple studies (example code for nuclear medicine imaging procedures)Nuclear medicine imaging codes may be billed in the same encounter when additional tracer imaging is performed; included as an example of contemporaneous nuclear studies.
    99000Handling and/or conveyance of specimens for transfer from the physician's office to a laboratoryUse when specimen handling charges are billed for off-site processing of labeled blood samples.
    93799Unlisted cardiovascular service or procedure (example placeholder for institution-specific assay procedures)Occasionally used if an institution has a specialized, unlisted assay related to red cell mass not captured by standard codes.
    36416Collection of capillary blood specimenAlternative blood collection method when venous access is difficult; may be used for some timed samples if clinically appropriate.

    Related Modifiers

    8 rows

    ModifierDescriptionWhen to Use
    22Modifier –22 (Increased Procedural Services) is used when a reported procedure is substantially more extensive than normally required. The CPT Manual and CMS state it may be appended only when the…- When to use: Append modifier -22 to a procedural CPT code when the service performed is substantially more extensive than the usual service described by that code — i.e., the procedure required…
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    78CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
    80CPT® Modifier 80 (Assistant Surgeon) is appended to a surgical CPT code when a physician (MD or DO) provides full, continuous assistance throughout the operative procedure. It is intended only for…- Use CPT Modifier -80 when a physician (MD or DO) serves as an assistant surgeon and provides full, continuous assistance throughout the entire operative procedure; append -80 to the surgical CPT…
    62Modifier 62 indicates that two surgeons function as co‑surgeons, each performing distinct parts of the same primary surgical procedure. It is appended to the primary procedure code (and any…- Use modifier -62 when two surgeons act as co‑surgeons (both primary surgeons) on a single definitive primary procedure, each performing distinct parts of the same surgical procedure (append -62 to…
    23Modifier -23 (Unusual Anesthesia) is used on anesthesia service CPT codes when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia…- Use modifier -23 only on anesthesia CPT codes (00100–01999) when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia because of…

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    2080P0206X
    207RH0000X
    363A00000X
    2086P0122X
    183500000X
    222Z00000X
    332800000X
    2471M2300X

    Related Payer Policy Updates

    Specialty: Nephrology1 / 2

    10 rows

    PolicyPayerEffective Date
    Vafseo (vadadustat) for anemia in CKD on dialysisCigna2026-08-15
    Metabolic Disorders - Cysteamine (Oral) Products for Individual and Family PlansCigna2026-08-15
    Kerendia (finerenone) — Coverage CriteriaBlue Cross Blue Shield - Iowa2026-08-05
    Voyxact (sibeprenlimab-szsl) — Prior authorization / medical necessity for primary IgA nephropathyColorado Rocky Mountain Health Plans2026-08-01
    Oxlumo (lumasiran) and Rivfloza (nedosiran) — Coverage Criteria (Ohio)Colorado Rocky Mountain Health Plans2026-08-01
    Korsuva (difelikefalin) — Medical Benefit Drug Coverage Criteria (Ohio)Colorado Rocky Mountain Health Plans2026-08-01
    Complement Inhibitors - EmpaveliCigna2026-08-01
    Tolvaptan (Jynarque)Cigna2026-08-01
    Nephrology - Filspari (sparsentan) coverageCigna2026-08-01
    Rivfloza (nedosiran) prior authorization for PH1UnitedHealthcare2026-08-01

    Related Codes

    CPT-78102-LIMITED-AREA-BONE-IMAGING-NUCLEAR-MEDICINE

    CPT 78102: Limited-Area Bone Imaging (Nuclear Medicine)

    CPT-78103-NUCLEAR-MEDICINE-BONE-SCAN

    CPT 78103: Multisite Bone Scintigraphy (Nuclear Medicine)

    CPT-78104-WHOLE-BODY-BONE-SCAN

    CPT 78104: Whole-Body Radionuclide Skeletal Scan

    CPT-78110-SINGLE-SAMPLE-PLASMA-VOLUME-DETERMINATION

    CPT 78110: Single-Sample Radioisotope Plasma Volume Determination

    CPT-78111-PLASMA-VOLUME-MULTIPLE-SAMPLE-METHOD

    CPT 78111: Plasma Volume Determination, Multiple Sample Method

    CPT-78120-RADIOLABELED-SINGLE-SAMPLE-RED-CELL-VOLUME

    CPT 78120: Single-Sample Radioisotope Red Cell Volume Determination

    CPT-78122-WHOLE-BLOOD-VOLUME-STUDY-ISOTOPE-DILUTION

    CPT 78122: Whole Blood Volume Study by Isotope Dilution

    CPT-78130-RED-BLOOD-CELL-SURVIVAL-STUDY-AUTOLOGOUS-RADIOLABEL

    CPT 78130: Red Blood Cell Lifespan Study, Radiolabeled Autologous RBC

    CPT-78140-LIVER-SPLEEN-RADIOLABELED-RED-BLOOD-CELL-SCAN

    CPT 78140: Liver and Spleen Scan with Radiolabeled Red Blood Cells

    CPT-78185-SPLEEN-RADIONUCLIDE-SCAN-SPLENIC-IMAGING

    CPT 78185: Radionuclide Spleen Study for Size/Position and Lesion Detection

    Showing 1–10 of 13

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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