FISCHBACH'S A MANUAL OF
LABORATORY AND DIAGNOSTIC TESTS.
11TH EDITION
• AUTHOR(S)FRANCES FISCHBACH;
MARGARET FISCHBACH; KATE STOUT
TESTBANKS
1) Ch. 1 — Diagnostic Testing
A 68-year-old man with confusion has a stat serum glucose
sent; result returns glucose 42 mg/dL. The nurse verifies the
sample was collected after a 12-hour fast. What is the most
appropriate immediate nursing action?
A. Recheck blood glucose with a point-of-care (fingerstick)
device and notify the provider if low.
B. Withhold oral intake until provider assessment because
fasting may lower glucose.
C. Document the result as expected for fasting and continue
routine monitoring.
,D. Draw additional labs for cortisol and insulin before giving
glucose to preserve diagnostic information.
Correct answer: A
Rationale — Correct: A serum glucose of 42 mg/dL is
hypoglycemic and can cause neuroglycopenic symptoms
(confusion). Per diagnostic testing principles, confirm with a
rapid point-of-care glucose and immediately notify the provider
for treatment. Nursing action prioritizes patient safety and
verification of the critical result.
Rationale — B: Withholding intake delays treatment; fasting
does not justify leaving a symptomatic hypoglycemic patient
untreated.
Rationale — C: This is unsafe; the value is critical and requires
intervention.
Rationale — D: Additional labs may be useful later, but
immediate correction of hypoglycemia takes precedence.
Teaching point: Confirm critical glucose values rapidly (POC)
and treat hypoglycemia immediately.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
2) Ch. 1 — Diagnostic Testing
A patient on warfarin has an international normalized ratio
(INR) ordered; the specimen was collected 2 hours after the
patient received their morning warfarin dose. Which preanalytic
,consideration most affects interpretation?
A. Time of specimen collection relative to dose (warfarin half-
life).
B. Tourniquet time during venipuncture.
C. Whether the laboratory uses PT or INR reporting.
D. Patient’s recent high-fat meal.
Correct answer: A
Rationale — Correct: Warfarin effects on coagulation are
related to steady-state and time since dosing; collecting too
soon after dosing may not reflect steady anticoagulation.
Accurate interpretation requires knowing timing relative to drug
dosing.
Rationale — B: Prolonged tourniquet time affects some
analytes but is less relevant to INR.
Rationale — C: PT vs. INR is important for reporting but not a
preanalytic timing concern.
Rationale — D: Dietary fat has minimal acute effect on INR.
Teaching point: Always document medication timing for
coagulation studies to interpret results accurately.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
3) Ch. 1 — Diagnostic Testing
A nurse collects a blood sample for potassium; the tube shows
visible hemolysis at the lab. The reported potassium is 6.2
, mEq/L. Which interpretation is most appropriate?
A. Treat immediately for hyperkalemia because 6.2 mEq/L is life-
threatening.
B. Recognize hemolysis can falsely elevate potassium; repeat a
non-hemolyzed specimen before treatment if the patient is
stable.
C. Assume the patient has true hyperkalemia because hemolysis
lowers potassium.
D. Ignore the result because hemolysis invalidates all chemistry
values.
Correct answer: B
Rationale — Correct: Hemolysis releases intracellular
potassium and can cause falsely elevated serum potassium. If
the patient has no ECG changes and is hemodynamically stable,
repeat collection with careful technique to confirm before
initiating potentially harmful therapy.
Rationale — A: Immediate treatment is warranted only if
clinical signs/ECG or repeat confirm true hyperkalemia.
Rationale — C: Hemolysis raises, not lowers, potassium.
Rationale — D: Hemolysis affects some analytes selectively; it
does not necessarily invalidate all tests but requires
interpretation and repeat when critical.
Teaching point: Hemolysis falsely elevates potassium; confirm
critical hyperkalemia before treatment when safe.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
LABORATORY AND DIAGNOSTIC TESTS.
11TH EDITION
• AUTHOR(S)FRANCES FISCHBACH;
MARGARET FISCHBACH; KATE STOUT
TESTBANKS
1) Ch. 1 — Diagnostic Testing
A 68-year-old man with confusion has a stat serum glucose
sent; result returns glucose 42 mg/dL. The nurse verifies the
sample was collected after a 12-hour fast. What is the most
appropriate immediate nursing action?
A. Recheck blood glucose with a point-of-care (fingerstick)
device and notify the provider if low.
B. Withhold oral intake until provider assessment because
fasting may lower glucose.
C. Document the result as expected for fasting and continue
routine monitoring.
,D. Draw additional labs for cortisol and insulin before giving
glucose to preserve diagnostic information.
Correct answer: A
Rationale — Correct: A serum glucose of 42 mg/dL is
hypoglycemic and can cause neuroglycopenic symptoms
(confusion). Per diagnostic testing principles, confirm with a
rapid point-of-care glucose and immediately notify the provider
for treatment. Nursing action prioritizes patient safety and
verification of the critical result.
Rationale — B: Withholding intake delays treatment; fasting
does not justify leaving a symptomatic hypoglycemic patient
untreated.
Rationale — C: This is unsafe; the value is critical and requires
intervention.
Rationale — D: Additional labs may be useful later, but
immediate correction of hypoglycemia takes precedence.
Teaching point: Confirm critical glucose values rapidly (POC)
and treat hypoglycemia immediately.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
2) Ch. 1 — Diagnostic Testing
A patient on warfarin has an international normalized ratio
(INR) ordered; the specimen was collected 2 hours after the
patient received their morning warfarin dose. Which preanalytic
,consideration most affects interpretation?
A. Time of specimen collection relative to dose (warfarin half-
life).
B. Tourniquet time during venipuncture.
C. Whether the laboratory uses PT or INR reporting.
D. Patient’s recent high-fat meal.
Correct answer: A
Rationale — Correct: Warfarin effects on coagulation are
related to steady-state and time since dosing; collecting too
soon after dosing may not reflect steady anticoagulation.
Accurate interpretation requires knowing timing relative to drug
dosing.
Rationale — B: Prolonged tourniquet time affects some
analytes but is less relevant to INR.
Rationale — C: PT vs. INR is important for reporting but not a
preanalytic timing concern.
Rationale — D: Dietary fat has minimal acute effect on INR.
Teaching point: Always document medication timing for
coagulation studies to interpret results accurately.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
3) Ch. 1 — Diagnostic Testing
A nurse collects a blood sample for potassium; the tube shows
visible hemolysis at the lab. The reported potassium is 6.2
, mEq/L. Which interpretation is most appropriate?
A. Treat immediately for hyperkalemia because 6.2 mEq/L is life-
threatening.
B. Recognize hemolysis can falsely elevate potassium; repeat a
non-hemolyzed specimen before treatment if the patient is
stable.
C. Assume the patient has true hyperkalemia because hemolysis
lowers potassium.
D. Ignore the result because hemolysis invalidates all chemistry
values.
Correct answer: B
Rationale — Correct: Hemolysis releases intracellular
potassium and can cause falsely elevated serum potassium. If
the patient has no ECG changes and is hemodynamically stable,
repeat collection with careful technique to confirm before
initiating potentially harmful therapy.
Rationale — A: Immediate treatment is warranted only if
clinical signs/ECG or repeat confirm true hyperkalemia.
Rationale — C: Hemolysis raises, not lowers, potassium.
Rationale — D: Hemolysis affects some analytes selectively; it
does not necessarily invalidate all tests but requires
interpretation and repeat when critical.
Teaching point: Hemolysis falsely elevates potassium; confirm
critical hyperkalemia before treatment when safe.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
