• Anti-D Rh_° Test
• D Factor
• Red cells (Rh)
• Rhesus factor
• Rh
• Rh Blood Typing
• Rh grouping
• Rh Typing
• Rh₁ (D) antigen
• Rhesus typing

• Lavender top tube
• 5-7 mL of venous blood
• Capillary tube from newborn heelstick or cord sample

Additional information

• Properly identify and label the tubes
• If it is anticipated that the client might need transfusion of any blood product, it is essential to band the client with blood bank band and properly label blood
• Include diagnosis, history of recent and past transfusions, pregnancy, and drug therapy, on the lab request form
• Handle the sample gently to prevent Hemolysis and send immediately to laboratory

• Detects the presence or absence of Rh₁ (D) antigen on red blood cell membranes by hemagglutination tests
• Rh (rhesus) blood group system is second in importance only to the ABO system. The major antigens of this system include D (formerly known as Rh_°), C, E, c, and e. Of these, only tests for the D antigen are performed routinely as it is the most immunogenic
• The Rh test is performed by mixing antiserum containing incomplete or blocking antibodies [anti-Rh_° (D)] with the individual's RBC's and then observing for agglutination. Presence of agglutination indicates the person's blood is typed Rh-positive, and absence indicates Rh-negative blood.
• If the individual is Rh-negative, further testing is done to identify the presence of Rh₁ (D) antigen in smaller amounts, also known as weak or D^u variant, and for phenotyping

• The indications of Rh factor testing (along with ABO blood group) include:
• To check and confirm the compatibility of donor and recipient blood before transfusion
• To identify Rh type before a person donates blood
• To identify the Rh type in stored blood
• To identify the Rh type in mother and infant to predict the risk of hemolytic disease of newborn (HDN)
• To detect Rh incompatibility in Rh-negative pregnant women with Rh-positive fetus
• As a routine screening test along with antibody titer to detect and monitor "sensitized" women
• To determine the need for Rh_o(D) immune globulin injection (RhoGAM™) in prenatal and postpartum period
• To detect the patient's Rh factor, where blood replacement is needed or when there is a risk of blood loss, such as:
• Anemia requiring transfusion
• Certain blood dyscrasias
• Liver disease
• Malignant tumors, as in leukemias
• Massive trauma
• Surgical needs [Blood products are typically ordered to be immediately available when significant blood loss is anticipated with major surgical procedures (Especially major orthopedic, abdominal, genitourinary, and cardiothoracic surgeries)]
• To detect Rh factor in context of forensic science and paternity testing (now mostly replaced by direct DNA testing)
• People who have D^u variant antigen are considered Rh-positive, but are transfused as Rh-negative recipients
• An Rh-negative individual is said to be "sensitized" or develop anti-D antibodies when exposed to Rh-positive blood/blood products or when Rh-positive fetal red cells enter the maternal circulation due to:
• Abdominal trauma
• Abortion (spontaneous or elective)
• Ectopic pregnancy
• Deliberate immunization, most commonly of repeated IV infusions of blood for the purpose of harvesting a given Rh antibody
• Invasive obstetric procedures such as amniocentesis, cordocentesis, amnionic villous sampling
• Previous pregnancies
• Previous transfusions
• Vaginal hemorrhage
• The risk of sensitization during pregnancy mainly depends on following 3 factors:
• Volume of transplacental hemorrhage
• Extent of maternal immune response
• Concurrent presence of ABO incompatibility
• If an Rh-negative pregnant woman with Rh-positive partner carries Rh-positive fetuses, she may develop maternal antibodies [Rh immunoglobulin G (IgG)] against fetal cells. These maternal antibodies in turn, may cross the placenta into the fetal circulation resulting in destruction of fetal blood cells that may result in a range of reactions, clinically seen as:
• Mildly affected infants may exhibit slight or no anemia and hyperbilirubinemia
• Moderately affected infants may have a combination of anemia and hyperbilirubinemia
• In severe cases, infants may develop kernicterus, a neurological syndrome that can lead to hypotonia, hearing loss, and mental retardation
• Hemolytic disease of newborn (HDN/erythroblastosis fetalis) is a life threatening condition in infants affected by Rh incompatibility, characterized by hemolytic anemia and jaundice. Most severe form of HDN is hydrops fetalis characterized by:
• High output cardiac failure
• Edema
• Ascites
• Pericardial effusion
• Extramedullary hematopoiesis
• U.S. Preventive Services Task Force (USPSTF) Recommendations:
• Strongly recommends Rh (D) typing and antibody testing for all pregnant women during their first antenatal visit
• Recommends repeated Rh (D) antibody testing in all Rh(D) negative women at 24-28 weeks' gestation, unless the biological father is known to be Rh negative too.
• If an Rh-negative mother delivers Rh-positive baby or aborts fetus whose Rh type is unknown, she should receive human anti-D immune globulin (Rh IgG) within 72 hrs to prevent hemolytic disease of neonate in future births
• Rh IgG dosing <13 weeks gestational age with vaginal bleeding or abortion is 50 micrograms (MICRhoGAM™)
• Rh IgG dosing for 13 weeks gestational age with vaginal bleeding, abortion or delivery of Rh positive infant is 300 micrograms (RhoGAM™)
• If an Rh-negative pregnant woman has been previously sensitized, human anti-D immune globulin is administered at 28-32 weeks of gestation. A postpartum blood sample must be evaluated for fetal-maternal bleed (Kleihauer Betke test) to determine the need for additional doses of Rh immunoglobulin.
• The American Association of Blood Banks recommends that a postpartum blood specimen of all Rh-D (Rh₁)-negative women (ie, those at risk for sensitization) be examined to detect a fetal maternal hemorrhage of >30 mL. A 1-mL dose of Rh IgG (RhoGAM™) contains 300 mcg and is sufficient to counteract the immunizing effects of 15 mL of packed red cells or 30 mL of whole blood
• Rh antibodies are highly immunogenic, and once developed, the recipient can only receive Rh-negative blood during subsequent red blood cell transfusions
• Rh deficiency syndrome (rare) occurs in individuals with absent (Rh null) or markedly reduced (Rh mod) Rh antigen. Such individuals may have hemolytic anemia, with the presence of stomatocytes, occasional spherocytes, and increased osmotic fragility. Splenectomy markedly improves the anemia.
• Antibodies for Rh₂ (C) are frequently found together with anti-Rh₁ (D) antibodies in the Rh-negative pregnant woman whose fetus or child is Rh positive and possess both antigens
• A recent study shows a significant association between Rh positivity and low levels of high-density lipoproteins in patients with multivessel coronary artery disease.

Additional information

• Interfering factors:
• Recent administration of blood, blood products, or dextran, causes cellular aggregation which resembles antibody-mediated agglutination
• Recent use of IV contrast media such as iodine, barium, and gadolinium
• Rough handling of sample leads to hemolysis
• Recent blood transfusion
• Pregnancy in past 3 months
• Abnormal proteins, cold agglutinins, and bacteremia, may interfere with testing
• Incidence of Rh types seen in different populations:
• Caucasians
• Rh(D)-Positive: 85%
• Rh(D)-Negative: 15%
• African-Americans & Asians
• Rh(D)-positive: 95%
• Rh(D)-Negative: 5%
• 50-75% of Rh-negative persons receiving a single Rh-positive unit will develop anti-D. Thus, all donors and recipients are routinely tested so that Rh-negative recipients can be given Rh-negative blood
• Related laboratory tests include:
• ABO blood grouping
• Blood urea nitrogen (BUN)
• Cold agglutinin
• Complete blood count
• Coombs' test - direct and indirect
• Gram staining
• Haptoglobin
• Immunoglobulin A
• Kleihauer-Betke
• PT and PTT
• Serum bilirubin
• Urinalysis

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

• Rh Positive: Agglutination (Seen in 85-90% of the population)
• Rh Negative: No agglutination (Seen in 10-15% of the population)

False Positive Results:

May occur when maternal RBC's have increased levels of hemoglobin F, as seen in hemoglobinopathies:

• Hereditary persistence of fetal hemoglobin
• Thalassemia
• Sickle cell anemia

Drugs which cause false-positive results or agglutination, include:

• Cephalexin
• Levodopa
• Methyldopa
• Methyldopate hydrochloride

N/A

N/A

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