LIVING THE LAB LIFE
A BLOG FOR ASCLS REGION V
Here is an interesting case that we saw in our blood bank recently:
An obstetric patient came to the laboratory to be drawn for a Type and Screen. She was scheduled for an elective cesarean section the next day, at thirty-eight weeks gestation.
Our initial results (in gel card):
ABORH: O negative
Since the patient was new to our blood bank, we performed a full antibody identification panel. Patient had 3+ reactivity on all D-positive cells. Additionally, she had 2+ reactivity on the D-negative, C-positive cell in the panel. This seemed to suggest that patient had an anti-D and anti-C; we had yet to determine whether the anti-D was active or passive (due to RhIg administration). We could not call to find out about past RhIg therapy, since the patient had been drawn as an outpatient and was no longer on site. Additionally, we could not contact her primary care provider, as it was late in the evening and the clinics were closed.
As per standard procedure, we contacted another local hospital blood bank where the patient had been seen for her prenatal work. That blood bank had identified anti-D, but did not have record of whether the anti-D was active or passive.
We sent out the patient’s specimen to our reference blood bank for antibody identification and titer results. The anti-D titer came out to 1:64 (a passive anti-D does not typically titer this high, so this suggests the anti-D is active). The reference lab also identified an anti-G, not an anti-C. The anti-G titer result was null.
Anti-G is one of the lesser-known antigens in the Rh system. It is present on all C-antigen positive cells and most D-antigen positive cells. For this reason, the anti-G antibody can look like anti-D and anti-C in patient testing. For transfusion purposes, it is not necessary to distinguish between anti-G or anti-D,-C, since any cells that are D-antigen and C-antigen negative will also be G-antigen negative. However, it is important to accurately identify anti-G in obstetric patients. Obstetric patients with anti-G are candidates for RhIg, whereas a patient with active anti-D is not. A blood bank reference laboratory can perform elution and adsorption studies to distinguish between anti-G and anti-D,-C. In this case of our patient, since she has both an active anti-D and anti-G, she is not a candidate for RhIg (we later confirmed with the patient’s care team that she had not received RhIg and it fact had been alloimmunized to the D-antigen years before).
Harmening, D. M. (2012). Modern Blood Banking & Transfusion Practices (6th ed.). Philadelphia: F.A. Davis.