CLINICAL LABORATORY SCIENCE
9TH EDITION
• AUTHOR(S)MARY LOUISE
TURGEON
TEST BANK
1.
Reference
Ch. 1 — Fundamentals of the Clinical Laboratory
Stem
A physician requests a stat potassium for an outpatient who
was just phlebotomized with a tourniquet left on for 6 minutes
and squeezed the fist repeatedly. The specimen is analyzed on
an automated electrolyte analyzer and returns a value of 5.9
mmol/L, higher than the patient’s previous baseline of 4.2
mmol/L. Which is the most appropriate laboratory
interpretation and immediate action?
,Options
A. Report the value as is — tourniquet does not cause
hyperkalemia significant enough to alter results.
B. Flag the result as possibly pre-analytically elevated due to
hemolysis or stasis and request a redraw with proper
technique.
C. Dilute the specimen 1:1 and re-run on the analyzer to
confirm concentration.
D. Add a hemolysis index correction factor to the result and
report the corrected value.
Correct answer
B
Rationale — Correct
The prolonged tourniquet and fist clenching produce
hemoconcentration and possible hemolysis, elevating
potassium. The appropriate laboratory action is to flag the
result as possibly pre-analytical and request a properly collected
redraw before reporting as definitive.
Rationale — Incorrect A
Tourniquet-induced stasis and hemolysis can significantly raise
potassium; reporting without comment risks harm.
Rationale — Incorrect C
Dilution changes matrix and may not correct hemolysis
artifacts; dilution is not standard for suspected pre-analytical
error.
,Rationale — Incorrect D
There is no validated universal “hemolysis index correction
factor” applicable across methods; best practice is recollection.
Teaching point
Prolonged tourniquet/fist clench can falsely elevate potassium
— recollect when suspected.
Citation
Turgeon, M. L. (9th ed.). Clinical Laboratory Science. Ch. 1.
2.
Reference
Ch. 1 — Fundamentals of the Clinical Laboratory
Stem
A midlevel provider orders a complete blood count (CBC) for a
newborn from a heel stick collected into a tube with visible
clotting. The automated hematology analyzer reports WBC 18.0
×10^9/L and platelet count 95 ×10^9/L. How should the lab
proceed?
Options
A. Release results; neonatal ranges are higher and clotting does
not affect counts significantly.
B. Reject the specimen for clotting and request a repeat venous
sample; report no results.
C. Manually smear and platelet estimate, note clotting, and call
the provider to recommend a redraw for platelet confirmation.
, D. Run the sample after vigorous vortexing to disperse the clot
and report corrected counts.
Correct answer
C
Rationale — Correct
Clotting can cause pseudothrombocytopenia; manual smear
and platelet estimate help determine if thrombocytopenia is
real. Simultaneously contact the clinician to recommend a
redraw if confirmation is needed—especially critical in
neonates.
Rationale — Incorrect A
Clotting can artifactually lower platelet counts; neonatal ranges
alone do not justify release without verification.
Rationale — Incorrect B
Immediate specimen rejection without providing any
preliminary verification (smear/estimate) delays urgent care;
better to provide interim assessment and recommend redraw if
needed.
Rationale — Incorrect D
Vortexing cannot reliably reverse clot-induced platelet
consumption and risks hemolysis; not acceptable.
Teaching point
Clotted specimens can cause pseudothrombocytopenia—
perform smear/estimate and contact clinician.
9TH EDITION
• AUTHOR(S)MARY LOUISE
TURGEON
TEST BANK
1.
Reference
Ch. 1 — Fundamentals of the Clinical Laboratory
Stem
A physician requests a stat potassium for an outpatient who
was just phlebotomized with a tourniquet left on for 6 minutes
and squeezed the fist repeatedly. The specimen is analyzed on
an automated electrolyte analyzer and returns a value of 5.9
mmol/L, higher than the patient’s previous baseline of 4.2
mmol/L. Which is the most appropriate laboratory
interpretation and immediate action?
,Options
A. Report the value as is — tourniquet does not cause
hyperkalemia significant enough to alter results.
B. Flag the result as possibly pre-analytically elevated due to
hemolysis or stasis and request a redraw with proper
technique.
C. Dilute the specimen 1:1 and re-run on the analyzer to
confirm concentration.
D. Add a hemolysis index correction factor to the result and
report the corrected value.
Correct answer
B
Rationale — Correct
The prolonged tourniquet and fist clenching produce
hemoconcentration and possible hemolysis, elevating
potassium. The appropriate laboratory action is to flag the
result as possibly pre-analytical and request a properly collected
redraw before reporting as definitive.
Rationale — Incorrect A
Tourniquet-induced stasis and hemolysis can significantly raise
potassium; reporting without comment risks harm.
Rationale — Incorrect C
Dilution changes matrix and may not correct hemolysis
artifacts; dilution is not standard for suspected pre-analytical
error.
,Rationale — Incorrect D
There is no validated universal “hemolysis index correction
factor” applicable across methods; best practice is recollection.
Teaching point
Prolonged tourniquet/fist clench can falsely elevate potassium
— recollect when suspected.
Citation
Turgeon, M. L. (9th ed.). Clinical Laboratory Science. Ch. 1.
2.
Reference
Ch. 1 — Fundamentals of the Clinical Laboratory
Stem
A midlevel provider orders a complete blood count (CBC) for a
newborn from a heel stick collected into a tube with visible
clotting. The automated hematology analyzer reports WBC 18.0
×10^9/L and platelet count 95 ×10^9/L. How should the lab
proceed?
Options
A. Release results; neonatal ranges are higher and clotting does
not affect counts significantly.
B. Reject the specimen for clotting and request a repeat venous
sample; report no results.
C. Manually smear and platelet estimate, note clotting, and call
the provider to recommend a redraw for platelet confirmation.
, D. Run the sample after vigorous vortexing to disperse the clot
and report corrected counts.
Correct answer
C
Rationale — Correct
Clotting can cause pseudothrombocytopenia; manual smear
and platelet estimate help determine if thrombocytopenia is
real. Simultaneously contact the clinician to recommend a
redraw if confirmation is needed—especially critical in
neonates.
Rationale — Incorrect A
Clotting can artifactually lower platelet counts; neonatal ranges
alone do not justify release without verification.
Rationale — Incorrect B
Immediate specimen rejection without providing any
preliminary verification (smear/estimate) delays urgent care;
better to provide interim assessment and recommend redraw if
needed.
Rationale — Incorrect D
Vortexing cannot reliably reverse clot-induced platelet
consumption and risks hemolysis; not acceptable.
Teaching point
Clotted specimens can cause pseudothrombocytopenia—
perform smear/estimate and contact clinician.
