Crossmatch Procedures & Interpretation Flashcards
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Read the first 7 Crossmatch Procedures & Interpretation flashcards as text
A donor-specific antibody (DSA) detected by single antigen bead assay with an MFI of approximately 3,000-5,000 would most likely produce which crossmatch results?
Answer: Negative CDC crossmatch but positive flow cytometric crossmatch
Moderate-strength DSAs are detectable by the highly sensitive FCXM but may be below the complement-fixing threshold needed for a positive CDC crossmatch result.
A historical (peak) crossmatch uses archived recipient serum to:
Answer: Detect prior sensitization events that may no longer be reflected in current serum
Historical serum represents the recipient's peak sensitization and is tested to uncover antibodies that may have waned but could return (anamnestic response) after transplantation.
On the standard NIH CDC scoring scale, a score of 8 indicates:
Answer: 81–100% cytotoxicity (strongly positive result)
The NIH CDC scale runs from 1 (negative, 0–10% dead cells) to 8 (strongly positive, 81–100% dead cells), with higher scores indicating more extensive complement-mediated lysis.
Which crossmatch technique has the LEAST sensitivity for detecting donor-specific antibodies?
Answer: Standard CDC crossmatch without wash steps
Standard CDC crossmatch requires sufficient antibody to activate the full complement cascade; it is the least sensitive, while SAB, FCXM, and AHG-CDC can all detect lower antibody concentrations.
In a standard CDC crossmatch protocol, which source of complement is most commonly used?
Answer: Exogenous rabbit serum added as an external complement source
Exogenous rabbit serum is the standard complement source in CDC crossmatch because it is potent and consistent; relying on human serum complement yields variable and often insufficient activity.
Chloroquine diphosphate treatment of donor cells before crossmatch testing is primarily used to:
Answer: Strip HLA class II antigens from the cell surface to reduce B-cell crossmatch sensitivity
Chloroquine raises endosomal pH and can strip HLA class II antigens from B-cell surfaces, allowing differentiation between anti-class I and anti-class II antibody reactivity.
In the context of a living donor kidney transplant, a positive T-cell CDC crossmatch using current recipient serum most commonly leads to:
Answer: Avoidance of transplantation or initiation of a desensitization protocol
A positive T-cell CDC crossmatch signifies high risk of hyperacute or acute humoral rejection; transplantation is typically contraindicated unless the patient undergoes successful desensitization.