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Information ⬇

Synonym/Acronym

direct antiglobulin testing (DAT).

Rationale

To detect associated conditions or drug therapies that can result in cell hemolysis, such as found in hemolytic disease of newborns, and hemolytic transfusion reactions.

Patient Preparation

There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

(Method: Hemagglutination) Negative (no agglutination).

Critical Findings and Potential Interventions ⬆ ⬇

N/A

Overview ⬆ ⬇

(Study type: Blood collected in a red-top tube and whole blood collected in a lavender-top [EDTA] tube; related body system: Circulatory/hematopoietic and immune systems.)

DAT detects in vivo antibody sensitization of red blood cells (RBCs). Immunoglobulin G (IgG) antibodies produced in certain disease states or in response to certain drugs can coat the surface of RBCs, resulting in cellular damage and hemolysis. When DAT is performed, RBCs are taken from the patient’s blood sample, washed with saline to remove residual globulins, and mixed with anti–human globulin reagent. If the anti–human globulin reagent causes agglutination of the patient’s RBCs, specific antiglobulin reagents can be used to determine whether the patient’s RBCs are coated with IgG, complement, or both. (See study titled “Blood Typing, Antibody Screen, and Crossmatch” for more information regarding transfusion reactions.)

Indications ⬆ ⬇

Interfering Factors ⬆ ⬇

Other Considerations

  • Tube methods for DAT are less sensitive than gel methods, and false-negative findings are possible in cases where weak, incompletely developed antigen sites on newborns’ RBCs may not allow detectable amounts of anti-A and/or anti-B to bind to the RBC membrane. Neonates who have received multiple intrauterine transfusions of antigen-negative (group O) cells may also have a negative DAT because the results represent circulating donated RBCs rather than the neonate’s native RBCs.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Positive Findings in

Antibodies formed during these circumstances or conditions attach to the patient’s RBCs, and hemolysis occurs. Agglutination is graded from 1+ to 4+ in manual testing systems, with 4+ being the strongest degree of agglutination. Automated testing systems can report 1+ to 4+ graded results, provide images of the tested material so laboratory professionals can interpret the results, or provide computer-assisted interpretation of the test results as positive or negative findings.

  • Anemia (autoimmune hemolytic, drug induced)
  • Hemolytic disease of the newborn (related to ABO or Rh incompatibility)
  • Infectious mononucleosis
  • Lymphomas
  • Mycoplasma pneumonia
  • Paroxysmal cold hemoglobinuria (idiopathic or disease related)
  • Passively acquired antibodies from plasma products
  • Postcardiac vascular surgery (increased incidence of positive DAT has been reported in patients following cardiac surgery, possibly related to mechanical RBC destruction while the patient is on cardiac bypass)
  • Systemic lupus erythematosus and other connective tissue immune disorders
  • Transfusion reactions (related to blood incompatibility)

Negative Findings in

  • Samples in which sensitization of erythrocytes has not occurred

Nursing Implications ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Explain that a blood sample is needed for the test.
  • Discuss how this test can assist in assessing for disorders that break down RBCs.

Procedural Information

  • If a cord sample is to be taken from a newborn, the parents are informed that the sample will be obtained at the time of delivery and will not result in blood loss to the infant.
  • Cord specimens are obtained by inserting a needle attached to a syringe into the umbilical vein.
  • The specimen is drawn into the syringe and gently expressed into the appropriate collection container.

Potential Nursing Actions

Verify informed and written consent has been obtained if blood transfusion is likely.

After the Study: Implementation & Evaluation Potential Nursing Actions

Avoiding Complications

  • Acute hemolytic reactions can be immediate and life threatening for patients of any age.
  • Assess and trend the newborn’s bilirubin and Hct levels. Increased bilirubin and decreased Hct may be indicative of RBC breakdown.
  • Kernicterus, or deposition of bilirubin in the brain, is a serious and significant development that can lead to permanent brain damage or death.
  • Chronic hemolytic anemia is also a significant condition requiring timely identification in order to treat the condition.
  • Transfusion reaction is a critical event that may occur in some patients. Signs and symptoms of blood transfusion reaction range from mildly febrile to anaphylactic. Symptoms may include chills, dyspnea, fever, headache, nausea, vomiting, palpitations and tachycardia, chest or back pain, apprehension, flushing, hives, angioedema, diarrhea, hypotension, oliguria, hemoglobinuria, acute kidney injury, sepsis, shock, and jaundice. Complications from disseminated intravascular coagulation (DIC) may also occur.
  • Possible interventions in mildly febrile transfusion reactions include slowing the rate of infusion, then verifying and comparing patient identification, transfusion requisition, and blood bag label. Patients should be closely monitored for further development of signs and symptoms. Administration of epinephrine may be ordered.
  • Possible interventions in a more severe transfusion reaction may include immediate cessation of infusion, notification of the HCP, keeping the IV line open with saline or lactated Ringer solution, collection of red- and lavender-top tubes for posttransfusion work-up, collection of urine, monitoring vital signs every 5 min, ordering additional testing if DIC is suspected, maintaining patent airway and blood pressure, and administering mannitol.

Treatment Considerations

  • Inadequate gas exchange related to RBC destruction can be a concern.
  • Symptoms of inadequate gas exchange include shortness of breath, orthopnea, cyanosis, increased heart rate, increased respiratory rate, and use of respiratory accessory muscles.
  • Interventions/actions related to inadequate gas exchange include the following: Auscultate and trend breath sounds. Administer ordered oxygen. Use pulse oximetry to monitor oxygen saturation. Collaborate with the health-care provider (HCP) to consider intubation and/or mechanical ventilation. Elevate the infant patient’s head. Administer ordered blood or blood products and monitor Hgb and Hct.

Safety Considerations

  • Explain the implications of positive test results in cord blood and newborn’s bilirubin and Hct levels. Note that results may indicate the need for immediate exchange transfusion. Facilities not equipped for neonatal exchange transfusion may elect to transfer the neonate to a facility where the appropriate level of care can be provided.
  • Observe the neonate closely and assess for the development of jaundice, an important way to identify a hemolytic process.
  • Facilitate the use of hand-off communication as a standardized approach to sharing information between caregivers. Vigilant use of this process can minimize the risk of error or injury during caregiver transition.

Injury Risk

  • Injury risk associated with Rh incompatibility, blood incompatibility can be a concern.
  • Symptoms of incompatibility include jaundice in newborn, infant cardiac stress (heart failure), and infant death.
  • Interventions/actions related to injury risk include the following: Obtain the patient's ABO & Rh, T&S, and XM. Administer prescribed Rh(D) immune globulin RhoGAM intramuscular (IM) or Rhophylac IM or IV to the patient. Administer prescribed iron supplements, erythropoietin, and blood transfusion to infant within blood transfusion guidelines. Monitor and trend the degree of neonatal jaundice and associated laboratory results for bilirubin, Hgb, and Hct. Facilitate use of a bilirubin light for the newborn.

Clinical Judgement

  • Consider how to address the emotional reaction of a transfusion hemolytic event.

Follow-Up Evaluation and Desired Outcomes

  • Acknowledges the implications of positive test results in the event of a transfusion-associated reaction.
  • Acknowledges the implications of positive test results in cord blood and reasons for recommendation of blood transfusion.
  • Patient states the purpose of RhIG (Rh immune globulin) or RhoGam injection in relation to future pregnancies.
  • Parents demonstrate proficiency in placing the infant under the bilirubin light and adhering to identified precautions.
  • Correctly states reportable transfusion reaction symptoms.