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Phlebotomy Order of Draw: Tube Order Practice

You must memorize the exact phlebotomy order of draw to pass your certification. Drawing blood tubes out of sequence causes additive carryover, which alters laboratory results and compromises patient care. This topic falls under Clinical Patient Care, the largest domain making up about 56% of your scored questions.

Phlebotomy order of draw chart: 1 yellow SPS blood culture, 2 light blue sodium citrate, 3 red or gold SST serum tube, 4 green heparin, 5 lavender potassium EDTA, 6 grey potassium oxalate and sodium fluoride, with the additive and tests for each tube
CLSI order of draw with tube colours, additives and tests. Additives carried between tubes are the classic source of false results.

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Three CCMA practice questions on order of draw — tap an answer for instant feedback. The app has 2,300+, timed and scored.

Question 1

A patient who was recently prescribed a narcotic analgesic for severe back pain presents to the clinic lethargic, and the medical assistant visually counts a respiratory rate of 8 breaths per minute. Which of the following conclusions should the assistant draw from this assessment?

▸ Why A is the answer

The normal respiratory rate for a healthy adult is between 12 and 20 breaths per minute. A rate of 8 breaths per minute is significantly below this normal threshold. When a patient is prescribed a narcotic analgesic, a known side effect is central nervous system depression, which often suppresses the respiratory drive and causes bradypnea. Option A is the correct conclusion because it links the abnormally slow rate to the likely pharmacological cause. Option B is incorrect because tachypnea means rapid breathing, which is the exact opposite of this patient's presentation. Option C is incorrect because eupnea refers to normal, unlabored breathing, and a rate of 8 is not normal. Option D is incorrect because orthopnea refers to difficulty breathing while lying flat, which is not indicated by a slow rate alone.

🔑 Key takeaway

Narcotic analgesics can depress the respiratory center, leading to an abnormally slow respiratory rate known as bradypnea.

Question 2

While collecting a comprehensive metabolic panel, an assistant is observed shaking the gold tube rapidly to mix the blood before placing it in the rack. The laboratory later reports elevated potassium levels. Which of the following best explains this result?

▸ Why C is the answer

Blood tubes must always be inverted gently. Shaking a tube rapidly causes hemolysis, which is the mechanical destruction of red blood cells. When red blood cells rupture, they release their intracellular contents, including large amounts of potassium, into the serum. This leads to a falsely elevated potassium reading on a metabolic panel. Option A is incorrect because while inadequate volume affects additive ratios in some tubes, it does not directly cause the severe cellular destruction seen here. Option B is incorrect because delayed centrifugation typically causes glucose to drop, rather than causing a massive spike in potassium from mechanical damage. Option D is incorrect because while a prolonged tourniquet can cause hemoconcentration, the direct action of vigorous agitation is the primary trigger for the mechanical hemolysis described in this scenario.

🔑 Key takeaway

Vigorous shaking of blood tubes causes hemolysis, which releases intracellular potassium into the serum and invalidates test results.

Question 3

After completing a blood draw on a patient with fragile veins, the assistant notices a small drop of blood on the outside of their left glove. What is the proper technique to remove the gloves?

▸ Why B is the answer

Removing contaminated personal protective equipment requires precise technique to avoid transferring pathogens to your own skin. Option B is correct because it follows the standard glove-to-glove technique; grasping the outside of the contaminated left glove with the still-gloved right hand ensures that the biohazard does not touch bare skin. Option A is incorrect because grabbing a bare wrist with a contaminated glove directly introduces the blood to the assistant's skin, causing a cross-contamination event. Option C is incorrect because hooking a bare finger inside a contaminated glove is the "skin-to-skin" step, which should only be performed on the second glove after the first has been safely removed. Option D is incorrect because washing disposable gloves degrades their material integrity and is never an acceptable substitute for proper doffing procedures.

🔑 Key takeaway

Proper glove removal utilizes a glove-to-glove and skin-to-skin technique to prevent transferring bloodborne pathogens to bare hands.

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CCMA practice question — order-of-draw
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Question 1

When using a winged infusion set to draw blood culture bottles and a complete blood count, which bottle should the medical assistant inoculate first to ensure accurate results?

  • A) The anaerobic bottle to prevent air exposure.
  • B) The lavender tube to secure the cell count.
  • C) The anaerobic bottle after the lavender tube.
  • D) The aerobic bottle to clear the tubing air.✓

💡 Key Takeaway

When using a butterfly needle, the aerobic blood culture bottle is drawn first.

Show rationale

When using a winged infusion set (butterfly needle), the air inside the tubing will be drawn into the first bottle attached. Therefore, the aerobic bottle must be inoculated first to clear the air from the tubing. Introducing air into the anaerobic bottle (Option A and Option C) would kill the anaerobic bacteria and invalidate the test. The lavender tube (Option B) must always be drawn after blood cultures to prevent cross-contamination of the culture with EDTA additives.

Question 2

A provider orders blood cultures, a partial thromboplastin time, a hemoglobin A1c, and a fasting blood glucose. Which sequence ensures compliance with CLSI guidelines?

  • A) Light blue, yellow SPS, gray, and lavender tubes.
  • B) Yellow SPS, lavender, light blue, and gray tubes.
  • C) Yellow SPS, light blue, lavender, and gray tubes.✓
  • D) Light blue, gray, yellow SPS, and lavender tubes.

💡 Key Takeaway

Blood cultures must always be drawn first to prevent bacterial contamination from other tube additives.

Show rationale

CLSI guidelines mandate drawing blood cultures in a yellow SPS tube first to maintain sterility. The light blue tube for coagulation follows, then the lavender tube for the A1c, and finally the gray tube for glucose. Option A incorrectly places coagulation before sterile cultures. Option B draws the EDTA tube before the citrate tube, risking additive carryover. Option D completely scrambles the sequence, risking massive cross-contamination and non-sterile culture collection.

Question 3

A medical assistant is preparing to draw a prothrombin time and a comprehensive metabolic panel using a winged infusion set. Which sequence represents the proper tube selection and order?

  • A) Draw the light blue tube, then the SST.
  • B) Draw a red discard, light blue, then SST.✓
  • C) Draw the SST, then the light blue tube.
  • D) Draw the light blue tube, then red discard.

💡 Key Takeaway

A discard tube is required before a light blue tube when using a winged infusion set.

Show rationale

When using a winged infusion set for a coagulation test, the tubing's dead space underfills the light blue tube, altering the critical blood-to-additive ratio. A red discard tube clears the air before drawing the light blue tube, followed by the SST for the metabolic panel. Option A ignores the dead space. Option C draws the SST first, risking clot activator cross-contamination. Option D places the discard tube incorrectly after the light blue tube.

Question 4

A patient requires a complete blood count and a basic metabolic panel. The assistant accidentally fills the lavender tube before the gold tube. What is the most likely consequence?

  • A) The metabolic panel will show falsely elevated potassium.✓
  • B) The complete blood count will show decreased platelets.
  • C) The metabolic panel will show falsely elevated calcium.
  • D) The complete blood count will show elevated hematocrit.

💡 Key Takeaway

Drawing an EDTA tube before a serum tube causes falsely elevated potassium levels due to additive carryover.

Show rationale

The lavender tube contains potassium EDTA. Drawing it before the gold tube causes additive carryover, leading to falsely elevated potassium and falsely decreased calcium on the basic metabolic panel. Option B is incorrect because EDTA preserves platelets rather than decreasing them. Option C is wrong because EDTA binds calcium, which would decrease rather than elevate it. Option D is incorrect as the hematocrit is unaffected by this specific order of draw error.

Question 5

A comprehensive metabolic panel returns with abnormally low calcium and high potassium. The medical assistant recalls drawing a lavender tube before the serum separator tube during the collection. Which of the following best explains these skewed laboratory results?

  • A) Inadequate fasting prior to the blood draw.
  • B) Prolonged tourniquet application during the collection procedure.
  • C) Insufficient inversion of the collected blood specimens.
  • D) Additive carryover from the incorrect draw sequence.✓

💡 Key Takeaway

Drawing an EDTA tube before a serum tube causes additive carryover, falsely altering calcium and potassium levels.

Show rationale

The standard order of draw is designed to prevent additives from one tube from contaminating the next. The correct answer is D because the lavender tube contains EDTA, which binds calcium and contains potassium. Drawing it before a serum separator tube causes additive carryover, leading to falsely low calcium and falsely high potassium in the serum sample. Option A is incorrect because fasting status affects glucose and lipids, not calcium and potassium in this specific pattern. Option B is wrong because while prolonged tourniquet time can elevate potassium, it does not cause the severe drop in calcium seen here. Option C is incorrect because insufficient inversion leads to microclotting in the lavender tube rather than altering the chemical composition of the subsequently drawn serum separator tube.

Question 6

A medical assistant obtains a capillary specimen for a comprehensive metabolic panel and a complete blood count. The assistant fills the serum separator tube before the EDTA tube. Which of the following complications will most likely affect the laboratory results?

  • A) The chemistry panel will show falsely decreased potassium levels.
  • B) The chemistry panel will show falsely elevated glucose levels.
  • C) The hematology panel will show falsely decreased platelet counts.✓
  • D) The hematology panel will show falsely elevated hematocrit levels.

💡 Key Takeaway

Delaying the EDTA capillary draw causes platelet clumping and falsely lowers platelet counts.

Show rationale

Capillary blood begins clotting immediately at the puncture site. If the EDTA tube is drawn after the serum tube, platelet clumping occurs, leading to a falsely decreased platelet count on the CBC. Option A is incorrect because potassium might actually increase from cell breakdown, not decrease. Option B is incorrect as glucose decreases over time, not increases. Option D is incorrect because hematocrit is not the primary value distorted by microclots.

Question 7

A medical assistant is performing a dermal puncture on an infant for a CBC and a comprehensive metabolic panel. The infant's heel is adequately warmed and cleaned. Which sequence should the assistant use to collect these specific microtubes?

  • A) Fill the lavender microtube first, then the serum microtube.✓
  • B) Fill the serum microtube first, then the lavender microtube.
  • C) Fill the green microtube first, then the lavender microtube.
  • D) Fill the lavender microtube first, then the green microtube.

💡 Key Takeaway

Capillary order of draw requires EDTA tubes to be collected before serum tubes.

Show rationale

For capillary draws, EDTA tubes (lavender) are collected first to prevent microclots from altering the CBC results. Serum tubes (gold/red) are collected last because clotting is expected. Option B is the venipuncture order, not capillary. Options C and D introduce a green tube, which is typically for plasma chemistries, but serum is standard for a CMP and EDTA still comes before heparin.

Question 8

A provider orders a capillary blood gas, a complete blood count, and a basic metabolic panel for an infant with respiratory distress. How should the medical assistant prioritize the collection of these specific microtubes?

  • A) Collect the blood gas first, then the lavender microtube, then the gold microtube.✓
  • B) Collect the lavender microtube first, then the blood gas, then the gold microtube.
  • C) Collect the blood gas first, then the gold microtube, then the lavender microtube.
  • D) Collect the gold microtube first, then the lavender microtube, then the blood gas.

💡 Key Takeaway

Capillary blood gases are always collected first, followed by EDTA tubes, then serum tubes.

Show rationale

In capillary collections, blood gas specimens must be collected first to minimize exposure to room air, which alters the results. The EDTA microtube (lavender) is collected next to prevent platelet clumping, followed by the serum tube (gold) for the metabolic panel. Option B incorrectly delays the blood gas, risking air exposure. Options C and D place the serum tube before the EDTA tube, which causes microclotting and ruins the hematology results.

Question 9

A medical assistant is performing a capillary puncture on an 18-month-old toddler for a complete blood count and a basic metabolic panel. Which of the following collection sequences is correct?

  • A) Fill the serum separator tube first to prevent cellular degradation.
  • B) Fill the light blue tube first to prevent coagulation cascade.
  • C) Fill the lavender microcollection tube first to prevent platelet clumping.✓
  • D) Fill the green microcollection tube first to prevent erythrocyte hemolysis.

💡 Key Takeaway

Capillary punctures require filling EDTA tubes first to minimize platelet clumping and microclots.

Show rationale

The correct sequence is C because the capillary order of draw differs from venipuncture; the EDTA (lavender) tube must be filled first to minimize platelet clumping and microclot formation in the sample. Option A is incorrect because serum tubes are drawn last in capillary collections, unlike in venipuncture. Option B is incorrect because light blue tubes (sodium citrate) are generally not used for capillary draws, as the ratio of blood to additive cannot be accurately maintained. Option D is incorrect because green tubes (heparin) should be drawn after EDTA tubes in capillary procedures.

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CCMA · Exam Simulator

When using a winged infusion set to draw blood culture bottles and a complete blood count, which bottle should…

A) The anaerobic bottle to prevent air expo
B) The lavender tube to secure the cell cou
C) The anaerobic bottle after the lavender
D) The aerobic bottle to clear the tubing a
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