Search all medical codes

Complement fixation tests, each antigen

CPT4 code

Name of the Procedure:

Complement Fixation Tests (CFTs)

  • Common name: Complement Fixation
  • Technical term: Complement Fixation Assay


Complement Fixation Tests (CFTs) are blood tests used to detect the presence of specific antibodies or antigens in a patient's blood. These tests are utilized to diagnose infections, autoimmune diseases, and other conditions where immune responses are significant.


CFTs are primarily used to detect and measure antibody levels in response to infections or autoimmune diseases. The goal is to identify the presence of specific infections by determining whether the immune system is responding appropriately to the suspected pathogen.


  • Symptoms of infectious diseases (e.g., fever, rash, fatigue)
  • Suspected autoimmune disorders
  • Screening for certain bacteria, viruses, or fungi
  • Monitoring immune response in patients with known infections


  • No fasting required.
  • Inform the doctor of any medications being taken, as some may need to be discontinued.
  • A simple blood test is usually all that is needed before the procedure.

Procedure Description

  1. A blood sample is drawn from the patient, typically from a vein in the arm.
  2. The sample is sent to a laboratory where it is mixed with a known antigen.
  3. Complement proteins are added to the mixture.
  4. If the patient's blood contains antibodies to the antigen, the complement will bind (fix) to the antigen-antibody complexes.
  5. This reaction is observed and measured to determine the presence and level of specific antibodies.


The blood draw takes about 5-10 minutes. Laboratory analysis may take several hours to a few days depending on the complexity of the test and laboratory workload.


The blood sample is collected in an outpatient setting such as a doctor's office, clinic, or hospital lab.


  • Phlebotomist or nurse for blood collection
  • Laboratory technician or technologist for sample analysis
  • Physician or specialist to interpret results

Risks and Complications

  • Minor risks: Bruising or bleeding at the site of blood draw, slight risk of infection.
  • Rare risks: Fainting or dizziness during the blood draw.


  • Accurate diagnosis of infections and some autoimmune conditions.
  • Helps guide effective treatment plans.
  • Non-invasive with minimal discomfort.


  • No specific recovery required from the blood draw.
  • Patients can usually resume normal activities immediately.
  • Follow-up appointments may be needed to discuss results and subsequent treatment.


  • ELISA (Enzyme-Linked Immunosorbent Assay): Useful for detecting specific antibodies or antigens with higher sensitivity.
  • PCR (Polymerase Chain Reaction): Identifies the genetic material of pathogens, often more specific.
  • Culture tests: Directly grow infectious agents but may take longer.

Patient Experience

  • Slight discomfort or pinch during blood draw.
  • Minor soreness or bruising at the puncture site.
  • Typically, no pain after the procedure.
  • Results discussion may cause anxiety but leads to clear treatment path.

Similar Codes