FISCHBACH'S A MANUAL OF
LABORATORY AND DIAGNOSTIC TESTS.
11TH EDITION
• AUTHOR(S)FRANCES FISCHBACH;
MARGARET FISCHBACH; KATE STOUT
TESTBANKS
Ch. 1 — Diagnostic Testing
Question 1
A 62-year-old patient is admitted with sepsis. Two sets of blood
cultures are ordered and drawn. The nurse collects the first set
and then delays the second set by 6 hours because of a staffing
shortage. Both sets later grow the same skin flora organism.
Which is the best interpretation and nursing action?
A. Both positive cultures confirm true bacteremia; notify the
provider immediately for targeted antibiotics.
B. Likely contamination from skin flora; document the delay and
repeat cultures before changing therapy.
C. Delay caused the same organism to colonize the second
,bottle; no further action needed.
D. Consider the results definitive because two positive sets are
more specific than one; continue current empiric therapy.
Correct answer: B
Rationale — Correct (B): Two positive cultures that grow
common skin flora may reflect contamination, especially when
collection timing and technique are suboptimal. The delayed
second draw increases the chance results reflect contamination
rather than true persistent bacteremia. Per diagnostic testing
principles, repeating properly timed cultures before escalating
therapy is appropriate while notifying the provider.
Rationale — Incorrect:
A: Two positives can indicate bacteremia but skin flora and poor
timing/technique reduce specificity; immediate targeted
therapy without verification risks inappropriate treatment.
C: The delay does not cause colonization of the bottle; it
increases contamination risk but does not justify no action.
D: Two positives may be convincing for some organisms, but
with likely contaminants and poor collection timing, they are
not definitive.
Teaching point: Properly timed, aseptic blood cultures minimize
contamination and guide therapy.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
,Ch. 1 — Diagnostic Testing
Question 2
A nurse prepares to draw a fasting glucose for a patient at 0800.
The patient had breakfast at 0700 claiming they "ate only
coffee." The nurse knows that preanalytic variables affect
results. What is the best nursing action?
A. Draw the sample now since the patient had only coffee —
results will still reflect fasting state.
B. Document the intake, proceed with the draw, and annotate
the lab requisition about the meal.
C. Cancel the order and replace it with a random glucose to
avoid invalid results.
D. Delay the draw for 8 hours from the breakfast time and
instruct the patient to remain NPO.
Correct answer: B
Rationale — Correct (B): If fasting status is uncertain, the nurse
should document the patient's intake and proceed if required
clinically, annotating the specimen to inform interpretation.
Many labs accept the specimen with an explanatory note rather
than cancelling.
Rationale — Incorrect:
A: Even coffee (with sugar/cream) can alter glucose; assuming
it’s still fasting is unsafe.
C: Canceling without provider input may delay care; a random
glucose may not meet the diagnostic intent.
, D: Delaying 8 hours may be impractical and requires provider
consent; documenting is the immediate correct action.
Teaching point: Always document deviations from pretest
instructions; annotate specimens for accurate interpretation.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
Ch. 1 — Diagnostic Testing
Question 3
A point-of-care (POC) glucose meter reads 42 mg/dL for an
elderly patient who appears confused. The meter is a CLIA-
waived device and has had control testing this morning. What is
the nurse’s best next step?
A. Treat immediately for hypoglycemia per protocol, then send
a venous glucose to the central lab for confirmation.
B. Repeat the POC test once; if it remains 42 mg/dL, no further
action is needed.
C. Ignore the POC result because CLIA-waived tests are
unreliable for critical values.
D. Contact the laboratory to perform immediate
chromatography to confirm.
Correct answer: A
Rationale — Correct (A): A critically low glucose with clinical
symptoms requires immediate treatment. CLIA-waived POC
results guide urgent care; confirmatory venous lab glucose can
LABORATORY AND DIAGNOSTIC TESTS.
11TH EDITION
• AUTHOR(S)FRANCES FISCHBACH;
MARGARET FISCHBACH; KATE STOUT
TESTBANKS
Ch. 1 — Diagnostic Testing
Question 1
A 62-year-old patient is admitted with sepsis. Two sets of blood
cultures are ordered and drawn. The nurse collects the first set
and then delays the second set by 6 hours because of a staffing
shortage. Both sets later grow the same skin flora organism.
Which is the best interpretation and nursing action?
A. Both positive cultures confirm true bacteremia; notify the
provider immediately for targeted antibiotics.
B. Likely contamination from skin flora; document the delay and
repeat cultures before changing therapy.
C. Delay caused the same organism to colonize the second
,bottle; no further action needed.
D. Consider the results definitive because two positive sets are
more specific than one; continue current empiric therapy.
Correct answer: B
Rationale — Correct (B): Two positive cultures that grow
common skin flora may reflect contamination, especially when
collection timing and technique are suboptimal. The delayed
second draw increases the chance results reflect contamination
rather than true persistent bacteremia. Per diagnostic testing
principles, repeating properly timed cultures before escalating
therapy is appropriate while notifying the provider.
Rationale — Incorrect:
A: Two positives can indicate bacteremia but skin flora and poor
timing/technique reduce specificity; immediate targeted
therapy without verification risks inappropriate treatment.
C: The delay does not cause colonization of the bottle; it
increases contamination risk but does not justify no action.
D: Two positives may be convincing for some organisms, but
with likely contaminants and poor collection timing, they are
not definitive.
Teaching point: Properly timed, aseptic blood cultures minimize
contamination and guide therapy.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
,Ch. 1 — Diagnostic Testing
Question 2
A nurse prepares to draw a fasting glucose for a patient at 0800.
The patient had breakfast at 0700 claiming they "ate only
coffee." The nurse knows that preanalytic variables affect
results. What is the best nursing action?
A. Draw the sample now since the patient had only coffee —
results will still reflect fasting state.
B. Document the intake, proceed with the draw, and annotate
the lab requisition about the meal.
C. Cancel the order and replace it with a random glucose to
avoid invalid results.
D. Delay the draw for 8 hours from the breakfast time and
instruct the patient to remain NPO.
Correct answer: B
Rationale — Correct (B): If fasting status is uncertain, the nurse
should document the patient's intake and proceed if required
clinically, annotating the specimen to inform interpretation.
Many labs accept the specimen with an explanatory note rather
than cancelling.
Rationale — Incorrect:
A: Even coffee (with sugar/cream) can alter glucose; assuming
it’s still fasting is unsafe.
C: Canceling without provider input may delay care; a random
glucose may not meet the diagnostic intent.
, D: Delaying 8 hours may be impractical and requires provider
consent; documenting is the immediate correct action.
Teaching point: Always document deviations from pretest
instructions; annotate specimens for accurate interpretation.
Citation: Fischbach, F., Fischbach, M., & Stout, K. (2024). A
Manual of Laboratory and Diagnostic Tests (11th ed.). Ch. 1.
Ch. 1 — Diagnostic Testing
Question 3
A point-of-care (POC) glucose meter reads 42 mg/dL for an
elderly patient who appears confused. The meter is a CLIA-
waived device and has had control testing this morning. What is
the nurse’s best next step?
A. Treat immediately for hypoglycemia per protocol, then send
a venous glucose to the central lab for confirmation.
B. Repeat the POC test once; if it remains 42 mg/dL, no further
action is needed.
C. Ignore the POC result because CLIA-waived tests are
unreliable for critical values.
D. Contact the laboratory to perform immediate
chromatography to confirm.
Correct answer: A
Rationale — Correct (A): A critically low glucose with clinical
symptoms requires immediate treatment. CLIA-waived POC
results guide urgent care; confirmatory venous lab glucose can
