Routine cord blood serologic testing - Who needs it? (An UPDATE)
If you recall, a member wrote that her institution does work ups on umbilical cord blood samples that are submitted from babies whose mothers are group O and/or Rh negative, and on babies whose mothers are known to have antibodies that could cause HDN. The member wanted to know if others felt it was necessary to do blood bank work ups on umbilical cord blood (including ABO grouping and Rh typing, and a DAT) obtained from babies who are born from group O mothers.
As an update to the discussion shown below, please see the recently published article from the Nov. 2001 issue of Transfusion entitled Practice guidelines for prenatal and perinatal immunohematology, revisited; authored by W. John Judd, for the Scientific Section Coordinating Committee of the AABB (Transfusion, Vol. 41, No. 11, 1445-1452, November 2001).
Several responses were submitted, including a portion of a soon to be published paper which may influence the community practice standard, as this paper includes advice set forth by the Scientific Section Coordinating Committee of the AABB [see response #3 below]. This paper is scheduled for formal publication in October 2001: [Judd WJ, for the Scientific Section Coordinating Committee of the AABB. Practice guidelines for prenatal-perinatal immunohematology revisited. Transfusion 2001;41:In press]. (See ABOVE update.)
- A blood banker in Nashville, Tennessee reported that at her hospital, umbilical cord blood samples are tested exactly as outlined by the questioner. One reason for this approach to testing is that the hospital has experienced a handful of babies with mild or worse ABO HDN. The responding member stated that she could not imagine convincing the pediatricians that most babies do not need to have their cord blood tested, until they are turning really yellow.
- Response #1 is interesting, in light of the opinion of a blood banker in Michigan who stated that at her hospital, they do NOT test the umbilical cord blood of all babies, and they have NOT done so for years. They only do umbilical cord blood testing on babies who are considered "yellow". The criteria for calling a baby 'yellow' are at the discretion of the clinician. Depending on which clinician is on service, the number of umbilical cord blood work ups per month may vary. This approach has caused a reduction in testing umbilical cord blood samples by 75%. The responding blood banker did not comment on any negative outcomes stemming from this approach.
- The above practices mentioned in responses #1 and #2 are interesting, in light of the following information which will soon be published in TRANSFUSION [Judd WJ, for the Scientific Section Coordinating Committee of the AABB. Practice guidelines for prenatal-perinatal immunohematology revisited. Transfusion 2001;41:In press]. The e-network forum is fortunate that the AABB has given permission for the CBBS to reproduce a portion of this upcoming article. The article is scheduled to appear in the October issue of TRANSFUSION, which has not yet been paginated, so the exact page numbers are not yet known. The information that follows pertains to the testing of cord, capillary (e.g., heel stick) or venous blood samples on newborn infants:
- In the absence of clinically significant unexpected antibodies in the maternal serum, NO TESTING of cord blood samples is required, except to aid in diagnosis, assist in neonatal care, or determine the RhIG candidacy of Rh-negative mothers. NOTE: Despite this statement, some institutions continue to perform ABO/Rh typing and a DAT on all newborns; such routine testing is not clinically indicated and should be discouraged. Others are somewhat selective, and routinely do an ABO/Rh and DAT on infants born to group O women; here, the intent seems to be to ascertain those infants at risk of ABO HDN. The mother is then advised to look for signs of neonatal jaundice and bring the infant back to the hospital when such signs appear. This practice has evolved with the advent of managed care programs and efforts to reduce the length of hospital stay, but cannot be condoned; all mothers should be counseled regarding neonatal jaundice.
- Blood from infants born to Rh-negative women should be tested for Rh, including a test for weak D. Note: If the infant is of a weak D phenotype, the mother is a candidate for RhIG and should be evaluated for excessive FMH. In this setting it is inappropriate to use the rosette test or any other anti-D based method to assess for excessive FMH (number of D sites on fetal RBCs will be low, resulting in false negative tests). Rather, methods should be used that detect hemoglobin F in fetal RBCs.
- ABO/Rh typing and a DAT should be done on the blood of all newborn infants of women with potentially significant, unexpected antibodies. Routine eluate preparation and testing is not indicated when confirmatory antibody identification studies have been performed on the maternal serum during the admission for delivery.
- In the absence of a maternal sample, the infant's blood can be used for compatibility testing.
- In the absence of maternal alloimmunization during pregnancy, serological testing of infant blood should be dictated by development of neonatal jaundice and/or unexplained anemia. Testing should initially focus on showing ABO incompatibility between fetus and mother. An ABO/Rh type and DAT should be done, although the DAT is often negative in ABO HDN. When there is fetal maternal ABO incompatibility, the infant's serum should be tested for unexpected antibodies by indirect antiglobulin technique against reagent group O RBCs, and with at least two examples of group A1 and/or group B RBCs. The presence of maternally derived IgG anti-A or anti-B in the infant's serum is sufficient evidence to support a diagnosis of ABO HDN. Eluate preparation and testing is not required.
- In the absence of fetal maternal ABO incompatibility, but with clinical evidence of HDN, an antibody in the maternal serum to a low prevalence (paternal) antigen should be considered. The infant's DAT will usually be strongly positive. An indirect antiglobulin test using maternal serum and paternal RBCs should be done. When ABO incompatibility exists between these samples, an eluate from the infant's RBCs can be tested against the paternal RBCs.
- blood banker from a large state hospital with a very active obstetric unit wrote that at her facility, a cord blood sample is sent to the Blood Bank from each newborn. These samples are held for 10 days BUT testing is performed only at the request of the nursery physician, i.e. jaundiced babies, etc. (See Webmaster comment below.) A daily printout of the blood types of the post-partum mothers is sent to the labor and delivery area which is then responsible for ordering the cord blood work ups for the Rh negative moms. Special testing is not performed for the group O mothers. They have been doing this for quite some time and it works well for her institution.
(EDITOR's NOTE: A previous e-Network issue (Nov., 2000) addressed the question of how long cord bloods may be kept for testing.)
- A blood banker in Texas reported that they only type babies that are born to Rh negative mothers. If that baby is Rh negative they do a test for weak D; if that is negative, the mother does not get Rh Immune Globulin. They do not type and perform DAT's on babies that are born to type O mothers, because the strength of a positive DAT does not correlate with the severity of the jaundice that the baby might or might not develop. Their doctors feel that treating the baby clinically is the best. At times the doctor will order a cord blood type and DAT, if the baby is exhibiting jaundice and the doctor needs to rule out ABO incompatibility.
- A blood banker in Northern California reports that at her institution,
the only newborns for which they do any umbilical cord blood testing are babies
born to Rh negative mothers. Those babies have an Rh type
done. Otherwise they do not do any cord blood work unless it is specifically
requested. According to the responding member, a "specific request" would
typically be submitted in the case of a baby with jaundice or a baby born
to a mother with anti-RBC antibodies, so that this practice would be consistent
with the practice at the Michigan hospital in response #2 above.
The responding member comments that it is up to the obstetrician to send
a cord sample for testing, so that it can be matched to any previous records
this blood bank lab might have. The reason for waiting to get a specific
request in this case is that the facility is a tertiary care facility,
and their reference lab performs prenatal workups on many women who don't
deliver at this facility. They also have many women deliver at their facility
whose prenatal work ups were done elsewhere. Mothers with anti-RBC antibodies are usually referred to their high risk obstetric group, and those physicians
arrange for appropriate neonatal follow-up.
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