CHT Crossmatch Procedures & Interpretation

Question 1

What is the primary purpose of performing a pretransplant crossmatch?

Accepted Answer

To detect preformed donor-specific HLA antibodies in the recipient's serum

Answer

The pretransplant crossmatch detects preformed donor-specific antibodies (DSAs) in the recipient that could cause hyperacute rejection upon transplantation.

Question 2

In a complement-dependent cytotoxicity (CDC) crossmatch, cell death is assessed by:

Accepted Answer

Exclusion of a vital dye such as eosin Y or trypan blue

Answer

CDC crossmatch uses vital dye exclusion — dead cells with compromised membranes take up the dye, allowing percent cytotoxicity to be calculated.

Question 3

A positive T-cell crossmatch using current recipient serum is clinically significant because it indicates:

Accepted Answer

Donor-specific anti-HLA class I antibodies in the recipient

Answer

T cells express HLA class I antigens (A, B, C), so a positive T-cell crossmatch indicates the recipient has preformed antibodies against donor HLA class I antigens.

Question 4

Dithiothreitol (DTT) treatment of recipient serum before crossmatch testing is used to:

Accepted Answer

Inactivate IgM antibodies by reducing their disulfide bonds

Answer

DTT cleaves the disulfide bonds that hold the pentameric IgM structure together, selectively inactivating IgM and allowing identification of IgG-mediated crossmatch reactivity.

Question 5

Which best describes an auto-crossmatch and its clinical use?

Accepted Answer

Testing recipient serum against the recipient's own lymphocytes

Answer

An auto-crossmatch tests recipient serum against the recipient's own cells to detect autoantibodies, which can cause false-positive crossmatch results if not identified.

CHT - Certified Histocompatibility Technologist Practice Test

CHT - Certified Histocompatibility Technologist Practice Test

CHT Crossmatch Procedures & Interpretation