82105

Alpha-fetoprotein (AFP); serum

CPT 82105 describes a laboratory procedure used to quantitatively measure alpha-fetoprotein (AFP) levels in a patient's serum. AFP is a glycoprotein that is normally produced during fetal development by the liver, yolk sac, and GI tract. In a healthy non-pregnant adult, AFP levels are typically very low or undetectable. However, this marker becomes clinically significant in two primary contexts: prenatal screening and oncology. During pregnancy, AFP is measured between the 15th and 20th weeks of gestation. Elevated serum levels may indicate fetal neural tube defects such as spina bifida or anencephaly, abdominal wall defects like gastroschisis, or the presence of multiple fetuses. Conversely, abnormally low levels, often analyzed alongside other markers like human chorionic gonadotropin (hCG) and estriol, are associated with an increased risk of chromosomal abnormalities, most notably Trisomy 21 (Down syndrome) and Trisomy 18. In the field of oncology, AFP serves as a critical tumor marker. It is frequently produced by malignant cells in hepatocellular carcinoma (HCC) and certain non-seminomatous germ cell tumors of the testes or ovaries, such as yolk sac tumors. For patients with chronic liver disease, such as cirrhosis or chronic hepatitis B/C, routine AFP monitoring is used for early detection of HCC. In patients already diagnosed with these malignancies, serial AFP measurements are used to monitor the effectiveness of surgical or chemotherapeutic interventions and to survey for potential disease recurrence. The laboratory process involves collecting a venous blood sample, separating the serum via centrifugation, and performing an immunoassay, such as an enzyme-linked immunosorbent assay (ELISA) or chemiluminescent immunoassay (CLIA), to determine the precise concentration of the protein.

Clinical Indications

  • Maternal serum screening for neural tube defects (NTDs) in the second trimester.
  • Screening for fetal chromosomal abnormalities such as Down syndrome (Trisomy 21) and Edwards syndrome (Trisomy 18).
  • Surveillance of patients with chronic liver disease (cirrhosis, Hepatitis B, or Hepatitis C) for hepatocellular carcinoma.
  • Diagnosis and monitoring of non-seminomatous germ cell tumors of the testis or ovary.
  • Evaluation of suspected hepatoblastoma in pediatric patients.
  • Post-treatment monitoring of AFP-secreting malignancies to detect recurrence.

Procedure Steps

  1. Confirm the clinical indication and, if for prenatal screening, verify the exact gestational age.
  2. Perform a standard venipuncture to collect a whole blood sample into a serum-separator tube (SST) or red-top tube.
  3. Allow the specimen to clot for 30 to 60 minutes at room temperature.
  4. Centrifuge the specimen to achieve complete separation of serum from cellular elements.
  5. Transfer the serum aliquot to a sterile transport tube, ensuring proper labeling and storage (refrigeration or freezing depending on transport time).
  6. Perform a quantitative immunoassay (e.g., ELISA, CLIA, or MEIA) using specific anti-AFP antibodies.
  7. Calculate the concentration of AFP in nanograms per milliliter (ng/mL) or International Units per milliliter (IU/mL).
  8. For prenatal tests, convert the raw value to Multiples of the Median (MoM) based on the patient's gestational age, weight, and ethnicity.
  9. Validate and report the final results to the ordering clinician.

Coding Guidelines

  • Report 82105 for measurements performed on serum samples.
  • Do not use 82105 if the AFP is measured in amniotic fluid; instead, use CPT 82106.
  • For the measurement of the AFP-L3 fraction (alpha-fetoprotein-L3), use CPT 82107.
  • If the AFP test is performed as part of a multianalyte assay with algorithmic analysis (MAAA) for fetal aneuploidy or NTD risk, use the specific MAAA code (e.g., 81508-81512) rather than 82105.
  • Check payer-specific local coverage determinations (LCDs) for frequency limits when using 82105 for cancer surveillance.
  • Use modifier 91 if a repeat test is required on the same day for a valid clinical reason, though this is rare for AFP.

Associated ICD-10 Codes