Mixed Deck — All ASCP Topics Flashcards

Root cause analysis (RCA) in the laboratory is conducted primarily to:

Answer: Identify the fundamental system or process failures that allowed an error to occur and prevent recurrence

RCA is a non-punitive, systematic process to identify the root causes (not just proximate causes) of errors. The goal is process improvement and error prevention through system-level changes rather than individual blame.

The anion gap (AG) is calculated from serum chemistry as:

Answer: Na+ minus (Cl- plus HCO3-)

Anion gap equals Na+ minus (Cl- plus HCO3-). Normal range is 8–12 mEq/L (or 12–16 if K+ is included). AG represents unmeasured anions (albumin, phosphate, sulfate, organic acids) and helps classify metabolic acidosis.

On a peripheral blood smear, target cells (codocytes) are most commonly associated with:

Answer: Liver disease, thalassemia, hemoglobin C disease, and post-splenectomy

Target cells have excess membrane relative to hemoglobin content, creating a bull's-eye appearance. They are classic for liver disease (altered lipid composition), thalassemia, hemoglobin C or SC disease, and post-splenectomy states.

A CSF sample from a patient with suspected cryptococcal meningitis should have which test performed immediately?

Answer: India ink preparation and cryptococcal antigen (CrAg) latex agglutination

India ink is a rapid test where the polysaccharide capsule of Cryptococcus neoformans or gattii excludes ink particles, creating a halo around the organism. Cryptococcal antigen (CrAg) latex agglutination is more sensitive (above 90%) and is the preferred rapid test.

A synovial fluid WBC of 50,000–200,000/µL with >90% PMNs is most consistent with:

Answer: Septic arthritis

Septic arthritis typically shows WBC >50,000/µL with >90% neutrophils; crystals and lower counts are seen in gout and inflammatory arthritis.

Microsatellite instability (MSI) testing is most relevant for which condition?

Answer: Lynch syndrome (hereditary nonpolyposis colorectal cancer)

Lynch syndrome is caused by germline mutations in mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2). Deficient MMR causes MSI — length changes in repetitive DNA sequences. MSI-H tumors in young patients prompt Lynch syndrome evaluation.

What is the correct order of draw when collecting multiple tubes via a single venipuncture?

Answer: Blood cultures → citrate → serum/SST → heparin → EDTA → fluoride

The CLSI-recommended order of draw minimizes additive carryover: blood cultures first (sterility), then citrate, serum, heparin, EDTA, and fluoride/oxalate.

Wright-Giemsa stain produces its polychromatic differential staining because it contains:

Answer: A mixture of acidic (eosin) and basic (methylene blue) dyes that react with acidic and basic cellular components

Wright-Giemsa is a Romanowsky stain containing eosin (acidic, orange-red, staining hemoglobin and eosinophilic granules) and methylene blue or azure B (basic, blue-purple, staining nuclei and basophilic granules). Together they produce the polychromatic differential staining of blood cells.

Which lipoprotein is considered 'good cholesterol' due to its role in reverse cholesterol transport?

Answer: HDL

HDL transports cholesterol from peripheral tissues back to the liver for excretion, reducing cardiovascular risk.

Which test is used to detect penicillin susceptibility differences between S. pneumoniae isolates?

Answer: 1-µg oxacillin disk diffusion or MIC testing

The 1-µg oxacillin disk screens for penicillin-non-susceptible pneumococci; MIC testing then determines exact susceptibility categories.

Which molecular technique provides the highest resolution for HLA allele-level typing?

Answer: Next-generation sequencing (NGS)

NGS provides the highest resolution allele-level HLA typing by generating phased sequence data, resolving ambiguities that arise with SSO, SSP, or Sanger sequencing. It is becoming the standard for unrelated donor searches in hematopoietic stem cell transplantation.

The indirect fluorescent antibody (IFA) test for ANA uses which substrate?

Answer: HEp-2 (human epithelial) cells

HEp-2 cells are the standard substrate for ANA IFA because their large nuclei display multiple patterns (homogeneous, speckled, nucleolar, centromere).

The direct antiglobulin test (DAT) detects:

Answer: Antibody or complement bound to patient's RBCs in vivo

The DAT uses antihuman globulin to detect IgG or complement already coating the patient's red blood cells.

Digital PCR (dPCR) differs from real-time qPCR primarily in that dPCR:

Answer: Partitions samples into thousands of individual reactions to provide absolute copy number without a standard curve

Digital PCR partitions the sample into thousands of individual droplets or wells, each containing zero or one target molecule. After PCR amplification, counting positive versus negative partitions via Poisson statistics provides absolute copy number without a standard curve.

The KOH preparation of skin scrapings showing hyphae and yeast ('spaghetti and meatballs') is diagnostic of:

Answer: Tinea versicolor (Malassezia furfur)

Malassezia furfur, the cause of tinea versicolor, produces characteristic short hyphae and round yeast cells resembling spaghetti and meatballs.

A specimen is discovered to be labeled with the wrong patient's name after analysis. What is the correct action?

Answer: Reject the specimen and collect a new properly labeled sample after notifying the provider

Mislabeled specimens are a critical patient safety issue; they must be rejected, the provider notified, and a new, correctly labeled specimen obtained.

Methylation-specific PCR (MSP) is used to detect which epigenetic modification?

Answer: DNA cytosine methylation at CpG sites

MSP detects DNA methylation at CpG dinucleotides. Bisulfite treatment converts unmethylated cytosines to uracil (read as thymine after PCR), while methylated cytosines are protected. MSP primers distinguish methylated from unmethylated alleles.

How long should a tourniquet remain applied during venipuncture to avoid hemoconcentration?

Answer: Less than 1 minute

Prolonged tourniquet use beyond 1 minute causes venous stasis and hemoconcentration, falsely elevating analytes such as proteins and potassium.

A patient with blood type A positive has which antigens on their red blood cells?

Answer: A antigen and Rh (D) antigen

Blood type A positive means the RBCs carry the A antigen (ABO) and the D antigen (Rh system).

A neonate presents with purpura fulminans and severely low protein C levels. This presentation is caused by:

Answer: Homozygous or compound heterozygous protein C deficiency

Neonatal purpura fulminans is caused by homozygous or compound heterozygous protein C deficiency (protein C activity below 1%), resulting in uncontrolled microvascular thrombosis affecting skin, brain, and eyes immediately after birth.