Necessary Laboratory Assessments for Infants Exposed to Maternal Alloantibodies

Please note that these are minimums and the exact timing of tests will be at the physician's discretion. Some infants will need labs more frequently, but medical literature states that all affected infants need a weekly hemoglobin/hematocrit check until approximately 12 weeks old to check for delayed onset anemia ¹. Anemia may be present without visible signs and can develop in infants who were not anemic in the hospital - blood tests are essential. When possible, use microtesting as anemia may be worsened by repeated testing. Multiple articles state not to give iron supplements without first testing the ferritin level. Infants with HDFN do not suffer from iron-deficiency anemia, but hemolytic anemia instead. In one study none of the infants with HDFN were found to be iron deficient, and that 70% of them suffered from iron overload instead ². Inappropriately administered iron supplements can be dangerous ^{2, 6}. For additional information about any of the topics listed here, see the Additional Reading by Topic page.

Birth

These tests are from umbilical cord blood. If the cord blood clots, it needs to be redrawn as soon as possible ^{3, 5}.

• Direct Antiglobulin Test (DAT) or Direct Coomb's Test ^{4, 7}
  • Indirect Antiglobulin Test (IAT) or Indirect Coomb's Test⁷: This is needed as well if the DAT comes back negative and mom has: anti-C, anti-c, anti-Fya, anti-Good, anti-H, anti-Jra, anti-M, or anti-Mta antibodies. These antibodies may not return a positive DAT but the infant still could be affected.
  • Antigen phenotype ⁷ (optional) - This test may be done to confirm the results of a DAT/IAT or in place of the IAT with one of the antibody exceptions above.

• Bilirubin ^{4, 7, 8}.
  • A cord bilirubin of ⩾2.05 mg/dL (pre-term) to 2.15 mg/dL (full-term) indicates need for phototherapy.
  • Note: Alloimmunization (isoimmune hemolytic disease) is a risk factor. All DAT/IAT positive infants born to alloimmunized mothers are automatically medium risk (infants born at 38 weeks gestation) or high risk (infants born before 38 weeks). DAT/IAT positive infants will not be low risk.
• Complete Blood Count (CBC) ⁷: including hemoglobin, hematocrit, neutrophil count, thrombocyte/platelet count, and a reticulocyte count (retic).

0-1 Week Old (Days 1-7)

• Bilirubin - checked every 4, 6 or 12 hours in the hospital ^{3, 4}.
• Bilirubin - checked daily when out of the hospital. This is especially important during days 4-6 when bilirubin due to alloimmunization tends to peak.
• Hemoglobin, or hematocrit ¹ - usually checked at least 1 other time this week besides birth.
• Reticulocyte count (retic)¹

1-2 Weeks Old

• Hemoglobin, or hematocrit - checked weekly¹(some doctors do 2x a week if <4 weeks old).
• Reticulocyte count (retic)¹
• Bilirubin - checked every other day if elevated.
• Neutrophil count and thrombocyte/platelet count.

3 Weeks Old

• Hemoglobin, or hematocrit - checked weekly ¹ (some doctors do 2x a week if <4 weeks old).
• Reticulocyte count (retic) ¹
• Bilirubin - 1-2x a week to be sure it is still going down.
• Neutrophil count and thrombocyte/platelet count may be repeated depending on the infants previous values.

4 Weeks Old - 12 Weeks Old

• Hemoglobin, or hematocrit - checked weekly ³. This is especially important for weeks four to six when newborns have a normal drop in hemoglobin. Infants suffering from HDFN can have a larger drop than normal and need their first transfusions during this window. This is not limited to infants whose mothers have had IUTs, but applies to all infants affected by alloimmunization. All affected infants need a weekly check until 12 weeks old or the hemoglobin is increasing for two to three weeks in a row.
• Reticulocyte count (retic) - checked weekly (timing optional, but it is not necessary to check more often than weekly) to see if the infant is making new blood.
• Other Tests - the neutrophil count and the thrombocyte/platelet count count may be repeated every two to four weeks if needed. Thrombocytopenia and neutropenia, are both common side effects of Hemolytic Disease of the Newborn¹. Neutropenia may last for up to 1 year in some cases.