Rh Antibody Titre and Direct Coombs Test in Maternal-Fetal Medicine
Introduction to Rh Antibody Titre and Direct Coombs Test
- The American College of Obstetricians and Gynecologists recommends measuring the concentration of anti-Rh antibodies in maternal serum using the Rh antibody titre test to screen for and monitor alloimmunization during pregnancy 1, 2
- The Rh antibody titre test is used as a screening test during prenatal care for all pregnant women to detect circulating red cell antibodies 3
- The American Academy of Pediatrics suggests that serial measurements of Rh antibody titre track antibody levels over time, with increasing titres suggesting higher risk of fetal anemia 4
- When titres reach a critical level, additional monitoring with middle cerebral artery Doppler studies may be initiated, as recommended by the American Institute of Ultrasound in Medicine 1
Clinical Applications of Direct Coombs Test
- A positive direct Coombs test result indicates antibody-coated red blood cells, suggesting immune-mediated hemolysis, according to the American Society of Hematology 5, 6
- In atypical hemolytic uremic syndrome, a negative direct and indirect Coombs test helps differentiate this condition from immune-mediated hemolysis, as stated by the National Institute of Diabetes and Digestive and Kidney Diseases 5, 6
- A negative direct Coombs test in a newborn with microangiopathic hemolytic anemia should prompt investigation for other causes such as thrombotic microangiopathy, as recommended by the American Academy of Pediatrics 5
Hemolytic Disease Diagnosis and Management
Test de Coombs Directo (DAT)
- In newborns with jaundice, a direct Coombs test is strongly recommended if the mother is Rh negative or has no prenatal typing, to detect ABO or Rh incompatibility 7
- The American Academy of Pediatrics recommends screening for irregular antibodies in all pregnant women to detect alloimmunization 7
Test de Coombs Indirecto (Screening de Anticuerpos)
- The American Academy of Pediatrics recommends that all pregnant women have antibody screening to detect potential hemolysis in the fetus or donor 7
- In Rh negative mothers, a Coombs indirect test is strongly recommended to detect anti-D antibodies 7