MLPAO Transfusion Medicine Case-Based Practice 2

Question 1

An emergency trauma patient arrives with massive hemorrhage. Blood type is unknown. What should the blood bank issue?

Accepted Answer

Issue group O Rh-negative (or O Rh-positive for males) uncrossmatched red blood cells and group AB plasma

Answer

In emergency massive hemorrhage, group O red blood cells are issued without waiting for typing. O Rh-negative is preferred for females of childbearing potential to prevent Rh sensitization. O Rh-positive can be used for males and post-menopausal females to conserve the limited O-negative supply. Group AB plasma is issued as the universal plasma donor type.

Question 2

A patient requires chronic transfusion for sickle cell disease. What special blood bank considerations apply?

Accepted Answer

Extended phenotype matching (Rh C, c, E, e, and K at minimum) to reduce alloimmunization risk, plus HbS-negative donor units

Answer

Sickle cell disease patients have a high alloimmunization rate (25-50%) due to antigen differences between donor (predominantly Caucasian) and recipient (predominantly African descent) populations. Canadian guidelines recommend extended matching for Rh (C, c, E, e) and Kell at minimum. Donor units should be sickle-negative (HbS-negative). Phenotypically similar donors should be actively recruited.

Question 3

A patient's antibody screen is positive with all three screening cells at the antiglobulin phase. What does this suggest?

Accepted Answer

Possible warm autoantibody, antibody to a high-frequency antigen, or multiple alloantibodies

Answer

Panreactivity (reactivity with all screening cells) suggests: 1) A warm autoantibody (reacting with a ubiquitous self-antigen), 2) An antibody to a high-frequency antigen (>99% of population), or 3) Multiple alloantibodies together reacting with all cells. An autocontrol (patient serum + patient cells) helps differentiate: if positive, autoantibody is likely; if negative, alloantibody to a high-frequency antigen is more likely.

Question 4

A patient has anti-Jk(a) identified 3 years ago but the current antibody screen is negative. Can the electronic crossmatch be used?

Accepted Answer

No — once a clinically significant antibody is identified, an antiglobulin crossmatch with antigen-negative units is always required, regardless of current screen results

Answer

A history of a clinically significant antibody (especially Kidd antibodies, which are known for evanescence) permanently disqualifies a patient from electronic crossmatch. Jk(a)-negative units must be selected and an antiglobulin crossmatch performed. This antibody history must be maintained in the blood bank records and communicated across institutions.

Question 5

A cord blood sample has a positive DAT with anti-IgG. The mother is group O Rh-positive and the baby is group A Rh-positive. What is the most likely cause?

Accepted Answer

ABO hemolytic disease of the newborn due to maternal anti-A (IgG) crossing the placenta

Answer

The most likely cause is ABO HDFN. Group O mothers produce IgG anti-A and anti-B (in addition to IgM), which can cross the placenta and coat the fetal A or B red cells. ABO HDFN is usually mild but can occasionally cause significant jaundice requiring phototherapy. An eluate from the baby's cells would confirm anti-A.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Transfusion Medicine Case-Based Practice 2