84155

Protein, total; serum, plasma, or whole blood

The CPT code 84155 describes the laboratory procedure for quantitatively measuring the total protein concentration in a sample of serum, plasma, or whole blood. Proteins are fundamental macromolecules essential for virtually every process within living cells. In the blood, total protein refers to the sum of all proteins present, primarily comprising albumin and globulins. Albumin, synthesized in the liver, is the most abundant protein and plays crucial roles in maintaining oncotic pressure, transporting hormones, fatty acids, and drugs, and contributing to acid-base balance. Globulins, a diverse group including immunoglobulins (antibodies), clotting factors, enzymes, and other transport proteins, are involved in immune defense, blood coagulation, and various metabolic functions.The measurement of total protein is a widely used diagnostic test that provides valuable insights into a patient's nutritional status, liver function, kidney function, and hydration levels. It can also help detect and monitor chronic inflammatory conditions and certain hematological disorders, such as multiple myeloma. The test typically employs colorimetric methods, most commonly the biuret method. In this method, peptide bonds in proteins react with copper ions in an alkaline solution to form a violet-colored complex. The intensity of this color is directly proportional to the concentration of protein in the sample and is measured spectrophotometrically. Results are reported in grams per deciliter (g/dL) and are interpreted in conjunction with other laboratory tests and clinical findings. Abnormal levels, whether elevated (hyperproteinemia) or decreased (hypoproteinemia), can point to a range of underlying medical conditions, necessitating further investigation.

Clinical Indications

  • Evaluation of nutritional status, particularly in cases of malnutrition or malabsorption.
  • Assessment of liver function and diagnosis or monitoring of liver diseases (e.g., cirrhosis, hepatitis).
  • Assessment of kidney function and diagnosis or monitoring of renal diseases (e.g., nephrotic syndrome, chronic kidney disease).
  • Investigation of unexplained edema or fluid retention.
  • Monitoring of chronic inflammatory conditions or systemic diseases.
  • Screening for or monitoring of monoclonal gammopathies (e.g., multiple myeloma, MGUS).
  • Evaluation of unexplained weight loss.
  • Assessment of hydration status (dehydration can lead to relative hyperproteinemia).
  • Pre-operative assessment to evaluate overall health status.
  • As part of a routine comprehensive metabolic panel (CMP).

Procedure Steps

  1. **Sample Collection:** A venous blood sample is collected from the patient, typically into a serum separator tube (SST) for serum or an EDTA tube for plasma. Whole blood samples are less common for this specific test but can be used.
  2. **Sample Preparation:** If serum or plasma is required, the blood sample is centrifuged to separate the cellular components from the fluid portion.
  3. **Reagent Addition:** An aliquot of the serum, plasma, or whole blood sample is mixed with a specific reagent, usually the biuret reagent (an alkaline solution of copper sulfate and sodium potassium tartrate).
  4. **Incubation:** The sample-reagent mixture is incubated at a controlled temperature for a specified period, allowing the copper ions to react with the peptide bonds present in the proteins, forming a characteristic violet-colored chelate complex.
  5. **Spectrophotometric Measurement:** The colored solution is then transferred to a cuvette, and its absorbance is measured at a specific wavelength (typically around 540-560 nm) using a spectrophotometer or automated chemistry analyzer.
  6. **Calculation:** The absorbance value is compared against a calibration curve generated using known protein standards. This allows for the precise calculation of the total protein concentration in the patient's sample.
  7. **Quality Control:** Internal and external quality control samples are run concurrently with patient samples to ensure the accuracy and reliability of the test results.
  8. **Result Reporting:** The total protein concentration, usually expressed in grams per deciliter (g/dL), is reported to the ordering physician, often along with the reference range.

Coding Guidelines

  • CPT code 84155 is used to report the quantitative measurement of total protein in serum, plasma, or whole blood.
  • This code is typically included as a component of a Comprehensive Metabolic Panel (CMP, CPT 80053). If a CMP is performed, individual components, including 84155, should not be billed separately unless a specific clinical necessity warrants an additional, non-panel total protein test on the same date of service (which is rare).
  • If total protein is ordered alone or as part of a custom panel not defined by a specific CPT panel code, 84155 can be billed individually.
  • Do not confuse 84155 with total protein measurement in other body fluids; for example, total protein in urine is reported with CPT code 84156.
  • Ensure that the medical record clearly documents the medical necessity for the total protein test, especially when billed individually outside of a standard panel.
  • Check for payer-specific policies regarding frequency limitations or specific diagnostic indications for total protein testing.

Associated ICD-10 Codes