ASCP Laboratory Operations 3

Question 1

Which specimen handling error is the most common preanalytical variable affecting test accuracy?

Accepted Answer

Hemolysis from improper venipuncture or sample handling

Answer

Hemolysis is the most common and impactful preanalytical error. Red cell lysis releases intracellular contents (potassium, LDH, AST, hemoglobin), falsely elevating many analytes and interfering with spectrophotometric assays.

Question 2

The order of draw for multiple tube collection is designed to prevent:

Accepted Answer

Cross-contamination of tube additives between specimens

Answer

Order of draw prevents carryover of additives between tubes. EDTA (purple) into a coagulation tube would falsely prolong PT and aPTT; skin puncture contamination into coagulation tubes is addressed by discarding the first few drops.

Question 3

A laboratory is investigating a false-positive HIV immunoassay. Which confirmatory testing approach is used under the current CDC algorithm?

Accepted Answer

HIV-1/HIV-2 antibody differentiation immunoassay, followed by HIV-1 NAT if indeterminate

Answer

The current CDC HIV diagnostic algorithm uses a 4th generation Ag/Ab combination immunoassay for screening, followed by an HIV-1/HIV-2 antibody differentiation immunoassay for confirmation. HIV RNA (NAT) is used when the differentiation assay is indeterminate.

Question 4

In a clinical laboratory, what is the purpose of internal quality control (IQC) material?

Accepted Answer

To monitor the analytical process for precision and accuracy between calibrations

Answer

IQC materials are tested with each run to monitor ongoing analytical performance. They verify that the method is performing within acceptable precision and accuracy limits, detecting reagent deterioration, instrument malfunction, or calibration drift between formal calibrations.

Question 5

A patient's hemoglobin is 15.2 g/dL but the MCV is 112 fL. This combination suggests:

Accepted Answer

Macrocytic process (likely B12 or folate deficiency)

Answer

MCV of 112 fL (normal 80–100 fL) indicates macrocytosis. Combined with near-normal hemoglobin, this pattern suggests early macrocytic processes such as B12 or folate deficiency, liver disease, alcohol use, hypothyroidism, or medications like methotrexate or hydroxyurea.

ASCP Practice Test

ASCP Practice Test

ASCP Laboratory Operations 3