Medical Technologist Test Medical Technologist Knowledge 4 — Questions and Answers
Question 1: The direct antiglobulin test (DAT) detects:
- Free antibodies in patient serum
- Antibodies or complement coating patient's red blood cells in vivo (Correct answer)
- ABO antibodies in donor plasma
- Rh antigens on donor cells
Correct answer: Antibodies or complement coating patient's red blood cells in vivo
The DAT uses anti-human globulin reagent to detect IgG antibodies or complement components already bound to RBCs in vivo.
Question 2: Which culture medium is selective and differential for gram-negative enteric organisms, inhibiting gram-positive bacteria?
- Blood agar
- MacConkey agar (Correct answer)
- Chocolate agar
- Thayer-Martin agar
Correct answer: MacConkey agar
MacConkey agar contains bile salts and crystal violet to inhibit gram-positive bacteria while differentiating lactose-fermenting from non-fermenting gram-negative rods.
Question 3: In a manual differential WBC count, 100 cells are counted. If 68 are neutrophils and the total WBC is 5,000/µL, the absolute neutrophil count (ANC) is:
- 340/µL
- 680/µL
- 3,400/µL (Correct answer)
- 6,800/µL
Correct answer: 3,400/µL
ANC = 68% × 5,000/µL = 3,400/µL, which is within the normal adult reference range.
Question 4: Which electrolyte abnormality is most consistent with a patient who has been vomiting repeatedly?
- Hyperkalemia and metabolic acidosis
- Hypokalemia and metabolic alkalosis (Correct answer)
- Hypernatremia and respiratory alkalosis
- Hyponatremia and metabolic acidosis
Correct answer: Hypokalemia and metabolic alkalosis
Repeated vomiting causes loss of HCl and fluid, leading to hypokalemia and metabolic alkalosis.
Question 5: The beta-lactamase test on a Staphylococcus aureus isolate is performed to determine:
- Methicillin resistance (MRSA)
- Penicillin resistance (Correct answer)
- Vancomycin susceptibility
- Oxacillin disk zone size
Correct answer: Penicillin resistance
Beta-lactamase production confers resistance to penicillin by hydrolyzing its beta-lactam ring; this guides antibiotic selection.
Question 6: In flow cytometry immunophenotyping, a cell population positive for CD19, CD20, and surface immunoglobulin is consistent with:
- T lymphocytes
- Natural killer cells
- Mature B lymphocytes (Correct answer)
- Monocytes
Correct answer: Mature B lymphocytes
CD19 and CD20 are pan-B-cell markers, and surface immunoglobulin expression confirms mature B lymphocyte identity.
Question 7: A specimen with a serum sodium of 118 mEq/L should prompt the medical technologist to:
- Discard and request a new sample
- Report the result and notify the ordering provider immediately (Correct answer)
- Repeat the test before reporting
- Flag only in the computer system
Correct answer: Report the result and notify the ordering provider immediately
A sodium of 118 mEq/L is a critical (panic) value and must be reported immediately to the ordering provider per laboratory policy.
Medical Technologist Test Medical Technologist Knowledge 4
The direct antiglobulin test (DAT) detects: