Exam Prep
Patient identification, tubes and order of draw, venipuncture, interferences and rejection, special specimens, storage and transport.
Independent practice questions written by Labologics. Not affiliated with DHA, DOH (formerly HAAD), SCFHS, Prometric or any exam body. Not recalled exam questions.
Before collecting blood, the patient should be identified using:
Answer: A — At least two identifiers, such as full name and medical record number or date of birth
Ask the patient to state their name when possible, and check against the request and ID band.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
When should blood tubes be labeled?
Answer: B — Immediately after collection, at the patient's side
Pre-labeling increases the risk of mislabeling, especially with similar names or twins.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
A blood sample arrives with no label. The correct action is:
Answer: C — Reject it and request a new, correctly labeled sample
Irreplaceable specimens (e.g., CSF, tissue) are handled by policy: contact the collector to correct the identification, never discard.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
The CLSI order of draw is:
Answer: D — Blood culture, citrate, serum, heparin, EDTA, fluoride
The order prevents additive carry-over, such as EDTA raising potassium and lowering calcium.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Which tube color contains sodium citrate for coagulation tests?
Answer: A — Light blue
Lavender = EDTA, gray = fluoride/oxalate, green = heparin, red = plain serum, gold = serum separator gel.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
EDTA prevents clotting by:
Answer: B — Chelating calcium
Heparin works by activating antithrombin. EDTA is used for CBC and HbA1c.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
Sodium fluoride tubes are used for glucose because fluoride:
Answer: C — Inhibits glycolysis (the enzyme enolase)
Without an inhibitor, glucose falls by about 5-7% per hour in unseparated blood.
Reference: Tietz Fundamentals of Clinical Chemistry
The blood-to-anticoagulant ratio in a 3.2% sodium citrate coagulation tube is:
Answer: C — 9:1
Underfilled tubes have too much citrate and give falsely prolonged PT/APTT. The Westergren ESR tube uses 4:1.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
When a winged (butterfly) set is used and the citrate tube is drawn first, you should:
Answer: A — Draw a discard tube first to remove air from the tubing
Air in the tubing causes underfilling.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Calcium should NOT be measured in which tube?
Answer: B — EDTA, citrate or oxalate tubes
These anticoagulants bind calcium.
Reference: Tietz Fundamentals of Clinical Chemistry
The main difference between serum and plasma is that plasma contains:
Answer: C — Fibrinogen (clotting factors)
Serum is the fluid left after clotting.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
The tourniquet should be left on for no more than about:
Answer: B — 1 minute
Prolonged use causes hemoconcentration, falsely raising proteins, calcium and potassium.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
For routine venipuncture, the site is cleaned with:
Answer: A — 70% isopropyl alcohol, allowed to air dry
Chlorhexidine or iodine is used for blood cultures. Use a non-alcohol antiseptic for blood alcohol tests.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
A patient has an IV infusion in the left arm. The best site is:
Answer: B — The other arm
If only that arm is available, draw below the IV after it has been stopped for at least 2 minutes, and note it.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
A patient faints during venipuncture. The first action is:
Answer: C — Remove the tourniquet and needle, stop the procedure and protect the patient from falling
Call for help and keep the patient lying down or head low until recovered.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Swelling and bruising at the venipuncture site is a:
Answer: D — Hematoma
Causes include the needle passing through the vein or not applying enough pressure afterward.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Which practice is likely to cause hemolysis?
Answer: A — Vigorous shaking or forcing blood through a small needle
Invert tubes gently (e.g., 8-10 times for EDTA).
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Hemolysis falsely increases:
Answer: B — Potassium, LDH and AST
Hemolyzed samples are rejected for potassium; request a new sample.
Reference: Tietz Fundamentals of Clinical Chemistry
Very high potassium with very low calcium, magnesium and ALP suggests:
Answer: C — EDTA contamination of the serum sample
Usually caused by wrong order of draw or pouring from an EDTA tube.
Reference: Tietz Fundamentals of Clinical Chemistry
A very high glucose with low potassium, calcium and protein suggests:
Answer: D — Contamination with dextrose IV fluid
Recollect from the opposite arm.
Reference: Tietz Fundamentals of Clinical Chemistry
Lipemia can falsely increase:
Answer: A — Hemoglobin on automated analyzers
It also causes pseudohyponatremia with indirect ISE methods. Fasting before lipid tests reduces it.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
A low platelet count with platelet clumps on the smear in an EDTA sample is best confirmed by:
Answer: B — Recollecting in sodium citrate and checking the blood film
EDTA-dependent platelet clumping is an in vitro artifact.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
A CBC sample is clotted. The correct action is:
Answer: C — Reject and request a new sample
Clots trap platelets and cells, giving false results.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
All tests on a sample are uniformly low. The most likely cause is:
Answer: D — Dilution (e.g., drawn from an IV line or above an infusion)
Check how and where the sample was collected.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Blood for ammonia should be:
Answer: A — Collected in EDTA or heparin, placed on ice and analyzed within about 30 minutes
Ammonia rises quickly in standing blood. If delayed, separate the plasma and freeze it.
Reference: Tietz Fundamentals of Clinical Chemistry
Lactate samples are collected in:
Answer: B — Fluoride/oxalate tubes, placed on ice
Avoid prolonged tourniquet and fist clenching.
Reference: Tietz Fundamentals of Clinical Chemistry
Arterial blood gas samples must be:
Answer: C — Collected in a heparinized syringe, free of air bubbles, and analyzed promptly
Air bubbles change pO2 and pCO2.
Reference: Tietz Fundamentals of Clinical Chemistry
The recommended blood volume for adult blood culture is:
Answer: B — 8-10 mL per bottle, 2 sets from separate sites
Volume is the most important factor in detecting bacteremia.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
A CSF sample for culture should be:
Answer: A — Sent to the lab immediately and processed at once, never refrigerated
N. meningitidis and H. influenzae are fragile. Late CSF is processed with a comment, not rejected.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
A urine sample cannot be tested within 2 hours. It should be:
Answer: B — Refrigerated (2-8 C)
At room temperature, bacteria multiply, pH rises, glucose falls and casts and cells break down.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
The best urine specimen for culture is:
Answer: C — Midstream clean-catch in a sterile container
Many squamous cells suggest contamination.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
For a 24-hour urine collection, the patient should:
Answer: D — Discard the first morning void, then collect all urine including the next morning's first void
Some tests need a preservative or refrigeration. A 24-hour urine is not suitable for culture.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
A patient cannot produce sputum for TB testing. The next step is usually:
Answer: A — Induced sputum with nebulized hypertonic saline, then bronchoscopy if needed
Collect early morning deep-cough samples on separate days.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
Serum or plasma should generally be separated from cells within:
Answer: B — 2 hours of collection
Serum tubes need about 30 minutes to clot before centrifugation.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
An uncentrifuged citrate sample for APTT (no heparin therapy) is generally stable at room temperature for:
Answer: B — 4 hours
PT samples are usually stable for 24 hours. For patients on unfractionated heparin, process within 1 hour.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods
Specimens are transported in:
Answer: D — Leak-proof, sealed containers in biohazard bags (triple packaging for shipping)
Request forms go in a separate pocket, away from the specimen.
Reference: CLSI GP41: Collection of Diagnostic Venous Blood Specimens
Peripheral blood smears and body fluid slides are commonly retained for at least:
Answer: B — 7 days
CAP: blood films and microbiology slides at least 7 days; check local rules.
Reference: Henry's Clinical Diagnosis and Management by Laboratory Methods