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Direct Antiglobulin Test/Coombs

DAT, Direct Coombs Test, Direct Antiglobulin/Direct Coombs (DAT), Antihuman Globulin Test, Direct Antiglobulin (DAT)/ Direct Coombs, Direct Antiglobulin Test/Coombs

Test Codes

EPIC: LAB5272, Beaker: DAT

Department

Blood Bank

Specimen Collection Criteria

Collect: One Pink-top EDTA tube, properly labeled. (Minimum Volume: 5.0 mL)
Also acceptable: (For Newborn Patients) One Pink-top EDTA Microtainer®, properly labeled. (Minimum Volume: 0.5 mL) Blood Bank may call for additional specimen for further testing if required.

It is extremely important that blood samples are accurately labeled. Inpatient labels must include the following information:

1. Patient's Name: Complete name, last name first. If the patient uses a first initial followed by a middle name, both must appear in proper order on the label.
2. Wrist Band Number:  Include the prefix letters, 4 numbers, and a suffix letter (example: BR1234T). Specimens lacking this complete information cannot be used for blood transfusion purposes.
3. Hospital Identification Number: The seven digit medical record number must be included on the label.
4. Date and Time Collected
5. Identification of Collector: Employee ID number must be on the sample tube or documented in the computer system.

For Beaumont Reference Laboratory (Outreach) patients, please refer to the Laboratory Bulletin on Laboratory Specimens: How to Label Correctly.

Physician Office/Draw Specimen Preparation

Maintain specimen at room temperature (20-26°C or 68-78.8°F) or refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Whole blood at room temperature (20-26°C or 68-78.8°F) or refrigerated (2-8°C or 36-46°F). 

Rejection Criteria

• Improperly labeled specimens.
• Specimens with inadequate volume.
• Clotted specimens.
• Hemolyzed samples will be tested only in emergency situations.

In-Lab Processing

Test the sample the same day that it is collected, if possible.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 48 hours
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): Specimens are held for a minimum of 7 days.

*Once a sample arrives in Blood Bank, it cannot be shared with other laboratories.

Laboratory

Farmington Hills Transfusion Medicine Laboratory (Blood Bank)
Grosse Pointe Transfusion Medicine Laboratory (Blood Bank)
Royal Oak Transfusion Medicine Laboratory (Blood Bank)
Troy Transfusion Medicine Laboratory (Blood Bank)
Dearborn Transfusion Medicine Laboratory (Blood Bank)
Taylor Transfusion Medicine Laboratory (Blood Bank)
Trenton Transfusion Medicine Laboratory (Blood Bank)
Wayne Transfusion Medicine Laboratory (Blood Bank)

Performed

Sunday – Saturday, 24 hours a day.
Results available within 2 hours of receipt in the Blood Bank for routine inpatient requests and within 8 hours of receipt in the Blood Bank for outpatient specimens.

Reference Range

Negative.

Test Methodology

Hemagglutination.

Interpretation

• Antihuman globulin reagent (AHG) is used to detect complement components and antibodies, which have bound to red cells but were unable to agglutinate the cells in saline medium. AHG reagents may be polyspecific (containing both anti-IgG and anti-C3d) or monospecific (anti-IgG, anti-C3d, etc.)
• Patients who test positive with polyspecific AHG will also be tested with monospecific anti-IgG and anti-C3d at an additional charge.
• Outreach patients who test positive with polyspecific AHG will have the reflex test Differential DAT performed.

Clinical Utility

The direct antiglobulin test detects in vivo sensitization of red cells. Direct antiglobulin testing is useful in the diagnosis of autoimmune hemolytic anemia, drug induced hemolytic anemia, and adverse reactions to transfusion due to RBC incompatibility.

CPT Codes

86880 (per reagent used).

Contacts

Last Updated

10/2/2023