Demonstrating the in vivo coating of red blood cells with IgG antibodies or the complement component (C3D)
Useful For
A direct antibody test is used in the investigation of hemolytic disease of the fetus and newborn, transfusion reactions, autoimmune hemolytic anemia, drug-induced immune hemolysis, and complement activation due to bacterial infection, autoantibodies or alloantibodies.
Method Name
Hemagglutination (Tube and Gel Methods)
- Polyspecific (Anti-IgG, -C3d): primary method is gel
- Antibody (Anti-IgG): primary method is gel
- Complement (Anti-C3b,-C3d): tube method
Aliases
Direct Coombs; Direct Antiglobulin Test; DAT, Direct Coombs
Specimen Type
Whole Blood
Specimen Required
Large lavender-top (EDTA) tube, approximately 7 mL
Cord Blood: small lavender-top (EDTA) tube, approximately 1 mL
After the patient is positively identified, the sample is drawn and fully labeled with the following information either electronically or handwritten:
- Patient’s full First and Last Name
- Date of Birth or Medical Record Number (MRN#)
- Date and Time specimen was drawn
- Blood Bank Armband Number (BBID) (see below for more information)
- Identify of the person who collected the specimen (Ex: Cerner ID or personnel initials)
All inpatients, or patients potentially receiving a transfusion, must have a blood bank armband (BBID) applied to their wrist and the Blood Bank ID (BBID) number written on the tube. This blood bank armband is a secondary patient identifier that helps ensure a safe and accurate transfusion. Specimens received without a blood bank armband will be rejected. See special instructions for more information.
Specimen Minimum Volume
1.0 mL of blood
Neonates/Heel Stick: If cord blood not collected/available. Lavender (EDTA) microtube 0.5 mL
Specimen Stability Information
Stable at room temperature for 24 hours.
Rejected Due To
- If the patient’s full first and last name and date of birth are not clear, accurate, and/or readable the specimen must be rejected.
- If the Blood Bank Armband Number (BBID) from the Blood Bank Armband is missing, inaccurate, illegible and/or can not be confirmed on all inpatient and outpatient potential transfusion specimens, the specimen must be rejected and sample redrawn.
- Specimens may be rejected for insufficient quantity and/or quality reasons (Ex: Hemolysis, dilution, etc).
- If there is any doubt as to the identity of the sample, a new sample must be obtained.
Special Instructions
- The person drawing the blood sample must confirm the patient’s identity by checking at least two independent identifiers before collected a specimen such as: first name, last name, date of birth, and medical record number. If possible, patient identification should be obtained verbally directly from the patient. The phlebotomist must not rely on a bed tag or on charts or records placed nearby. After positively identifying the patient, the sample is drawn and fully labeled with the following information either electronically or handwritten: Patient’s full first and last name, date of birth or medical record number (MRN#), date and time specimen was drawn, Blood Bank Armband Number (see below for more information), and identify of the person who collected the specimen (Ex: Cerner ID or personnel initials).
- All inpatients, or patients potentially receiving a transfusion, must have a Blood Bank Armband applied to their wrist and the Blood Bank Armband Number (BBID) number written on the tube. Please write the number clearly and do not use a gel pen (anything written in gel pen smears as the specimen is transported in a bag to the lab). This blood bank armband is a secondary patient identifier that helps ensure a safe and accurate transfusion. Specimens received without a blood bank armband ID will be rejected.
Performing Laboratory
Glens Falls Hospital Laboratory
Reference Values
Polyspecific (Anti-IgG, -C3d)
- Negative: No agglutination and no hemolysis is a negative test result. A negative result indicates the absence of detectable IgG and/or C3b-C3d on the red blood cells.
- Positive: Agglutination and/or hemolysis of the red blood cells is a positive test result. A positive test result indicates the presence of IgG and/or C3d on the red blood cells. Positive results in the polyspecific DAT test are then further tested against Anti-IgG and anti-C3b/C3d tube testing method to determine if the positive reaction is from antiglobulin, complement, or both.
Antibody (Anti-IgG)
- Negative: No agglutination and no hemolysis of the red blood cells is a negative test result. A negative result indicates no antiglobulin (IgG) coating the red blood cells.
- Positive: Agglutination and/or hemolysis of the red blood cells is a positive test result. Positive results with IgG indicate the presence of antiglobulin (IgG) on the red blood cells.
Complement (Anti-C3b,-C3d):
- Negative: Indicates the absence of detectable C3 on the red blood cells.
- Positive: Indicates the presence of complement (usually C3d) on the red blood cells.
Day(s) and Time(s) Performed
24 hours 7 days a week
Analytical Time
STAT turn around time approximately 1 hour.
Routine inpatient samples around time is approximately 2- 4 hours.
Routine outpatient samples to 1-2 days.
Specimen Retention Time
10 Days
Reflex Tests
If DAT Polyspecific (Anti- IgG, -C3d) is positive, further testing for anti-IgG gel cards and anti-C3b/C3d tube testing method will be added.
Analytical Time
STAT turn around time approximately 1 hour.
Routine inpatient samples around time is approximately 2- 4 hours.
Routine outpatient samples to 1-2 days.