Mixed Deck — All CHT Topics Flashcards

Which accreditation organization specifically accredits histocompatibility laboratories in the United States?

Answer: American Society for Histocompatibility and Immunogenetics (ASHI)

ASHI provides specialty accreditation for histocompatibility laboratories, setting standards specific to HLA testing, crossmatching, and transplant immunology beyond CLIA requirements.

Which HLA antibody class is most commonly detected in sensitized transplant patients?

Answer: IgG

IgG HLA antibodies are the most clinically relevant and most commonly detected class in transplant patients, as they cross the placenta, fix complement, and mediate AMR.

What is a 'null' allele in HLA nomenclature?

Answer: An allele with a stop codon or splice mutation resulting in no cell-surface expression

Null alleles (designated 'N' in the allele name) harbor mutations such as premature stop codons that prevent surface expression of the HLA protein.

What is a key aspect of Data Interpretation & Clinical Application?

Answer: Data Interpretation & Clinical Application standard

Effective Data Interpretation and Clinical Application are guided by specific standards to ensure accuracy and consistency. These standards provide frameworks and criteria for analyzing results, drawing valid conclusions, and applying them appropriately in patient care or research. Following established standards minimizes errors and optimizes the utility of data in clinical decision-making.

What is a key aspect of Laboratory Techniques & Testing Procedures?

Answer: Laboratory Techniques & Testing Procedures standard

A key aspect of Laboratory Techniques & Testing Procedures is adhering to established standards. This ensures accuracy, reliability, and reproducibility of results, which are paramount in a field like histocompatibility where patient lives depend on precise testing.

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.

A 'virtual crossmatch' in transplantation is performed by:

Answer: Comparing recipient antibody specificities (from solid-phase assay) against the donor's HLA type

Virtual crossmatch matches the recipient's HLA antibody profile (from Luminex single antigen bead testing) against the donor's HLA typing to predict physical crossmatch outcome without requiring donor cells.

Which chromosome carries the HLA gene complex in humans?

Answer: Chromosome 6

The HLA gene complex (MHC) is located on the short arm of chromosome 6 at region 6p21.

What is 'delta check' monitoring in the histocompatibility laboratory?

Answer: Comparing a current patient result to a previous result to flag unexpected changes that may indicate an error

Delta checks compare current test results against a patient's prior results; unexpected changes (e.g., new HLA allele appearing) trigger investigation for specimen mix-up or error.

The antihuman globulin (AHG)-enhanced CDC crossmatch increases sensitivity by:

Answer: Crosslinking IgG bound to cell-surface HLA, increasing complement-fixing complexes

AHG (anti-human IgG) binds to IgG already attached to cell-surface HLA antigens, crosslinking them and creating larger immune complexes that more efficiently fix complement.

Which allocation policy requires that organs be offered locally, then regionally, then nationally?

Answer: The former geographic-based UNOS allocation policy (largely replaced by continuous distribution for some organs)

UNOS historically used local-regional-national geographic sequencing for organ offers, though newer continuous distribution models for hearts and livers prioritize medical urgency and compatibility over geography.

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.

In kidney allocation, what does 'CPRA' primarily determine?

Answer: Priority points that highly sensitized candidates receive, increasing their chances of receiving an organ

High CPRA recipients receive additional priority points in UNOS kidney allocation policy to compensate for their reduced compatible donor pool.

What type of rejection occurs within minutes of transplant due to preformed antibodies?

Answer: Hyperacute rejection

Hyperacute rejection is a severe and immediate form of transplant rejection that occurs within minutes to hours after transplantation. It is caused by pre-existing antibodies in the recipient's blood that recognize donor antigens, leading to rapid destruction of the transplanted organ.

Which technique is commonly used to detect HLA antibodies?

Answer: ELISA

Enzyme-Linked Immunosorbent Assay (ELISA) is a widely used laboratory technique to detect and quantify antibodies, including HLA antibodies, in a patient's serum. This method is crucial for pre-transplant screening to assess the recipient's sensitization status and identify potential risks of rejection.

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

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

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

What is a 'Donation after Circulatory Death' (DCD) donor?

Answer: A donor whose death is declared by circulatory criteria after planned withdrawal of life support

DCD donors are individuals whose death is determined by irreversible cessation of circulatory function, typically after deliberate withdrawal of life-sustaining treatment.

What is a key aspect of Quality Assurance & Regulatory Compliance?

Answer: Quality Assurance & Regulatory Compliance standard

Quality Assurance and Regulatory Compliance (QA/RC) fundamentally rely on established standards. These standards define the specific requirements, guidelines, and procedures that must be followed to ensure the quality, safety, and efficacy of products or services. Adhering to these standards is crucial for maintaining compliance with regulatory bodies and achieving consistent, reliable outcomes.

What is a key aspect of Laboratory Techniques & Testing Procedures?

Answer: Laboratory Techniques & Testing Procedures standard

A key aspect of Laboratory Techniques & Testing Procedures is adhering to established standards. This ensures accuracy, reliability, and reproducibility of results, which are paramount in a field like histocompatibility where patient lives depend on precise testing.

Which cells are primarily involved in recognizing histocompatibility antigens?

Answer: T lymphocytes

T lymphocytes, specifically helper T cells and cytotoxic T lymphocytes, are the primary immune cells responsible for recognizing histocompatibility antigens presented by MHC molecules. They play a critical role in mediating cellular immunity and are key players in transplant rejection if the donor and recipient tissues are not compatible.