6.1 High-Yield Recap
Key Takeaways
- The CLSI GP41 order of draw is blood culture, light blue, red/SST, green, lavender, gray — carryover of one tube's additive into the next is the reason the sequence is fixed
- Lavender (EDTA) inverts 8-10 times for a CBC; light blue (3.2% sodium citrate) requires a 9:1 blood-to-additive fill for coagulation testing
- Routine venipuncture uses 70% isopropyl alcohol, blood cultures use chlorhexidine gluconate, and blood alcohol levels use a non-alcohol antiseptic such as benzalkonium chloride
- OSHA 29 CFR 1910.1030 governs bloodborne pathogens; PPE is donned gown, mask, eye protection, then gloves last, and removed in reverse
- An unlabeled or mislabeled specimen is the single most common reason a sample is rejected, and hemolysis falsely elevates potassium
High-Yield Recap Across All Five Domains
Quick Answer: On the NHA Certified Phlebotomy Technician (CPT) exam, more than half of your 100 scored items come from just two domains — Routine Blood Collections (28%) and Safety and Compliance (26%). If you know the order of draw cold, can match every tube to its additive and its test, and can recite OSHA and PPE rules without hesitating, you control the majority of the score.
This section pulls the most-tested facts out of every domain so you can confirm them in one pass during your final review. Nothing here is new material — it is a deliberate consolidation of the highest-yield rules. Spell-out reminder: PPE is personal protective equipment, OSHA is the Occupational Safety and Health Administration, CLSI is the Clinical and Laboratory Standards Institute, EDTA is ethylenediaminetetraacetic acid, CBC is complete blood count, and PT/INR/aPTT are prothrombin time / international normalized ratio / activated partial thromboplastin time.
Domain Weights — Know Where Points Live
| Domain | Weight | Scored items (of 100) |
|---|---|---|
| Routine Blood Collections | 28% | 28 |
| Safety and Compliance | 26% | 26 |
| Patient Preparation | 20% | 20 |
| Processing | 14% | 14 |
| Special Collections | 12% | 12 |
The practical takeaway: Routine + Safety = 54 of 100 scored items. A weak special-collections domain costs at most 12 points; a weak order-of-draw understanding can sink the whole exam.
Order of Draw, Additives, and Inversions
The order of draw exists to prevent additive carryover — anticoagulant from one tube contaminating the next and producing a wrong result. The CLSI GP41 sequence is the standard the NHA CPT tests:
| # | Tube (stopper) | Additive | Primary use | Inversions |
|---|---|---|---|---|
| 1 | Blood culture (yellow/SPS bottles) | Sodium polyanethol sulfonate (SPS) | Sterile cultures, drawn first | 8-10 (gentle) |
| 2 | Light blue | 3.2% sodium citrate | PT/INR, aPTT, coagulation | 3-4 |
| 3 | Red (plain) / Gold SST | None / clot activator + gel | Serum chemistry, serology | Red 0, SST 5 |
| 4 | Green | Heparin (sodium/lithium) | STAT chemistry, plasma | 8-10 |
| 5 | Lavender | EDTA | CBC, ESR, hematology | 8-10 |
| 6 | Gray | Sodium fluoride / potassium oxalate | Glucose, lactate, blood alcohol | 8-10 |
The Three Most-Tested Carryover Traps
- EDTA into a chemistry tube chelates calcium and elevates potassium — lavender is drawn after green and serum tubes for this reason.
- Clot activator into a coagulation tube triggers clotting and ruins a PT/INR — light blue is drawn before any clot-activator tube.
- A short-filled light blue tube changes the 9:1 blood-to-citrate ratio, falsely prolonging coagulation results; the tube must fill to the indicated line.
Safety, OSHA, and PPE
Safety and Compliance is 26% of the exam, and OSHA rules generate predictable items.
- OSHA Bloodborne Pathogens Standard: 29 CFR 1910.1030. Employers must offer the hepatitis B vaccine at no cost (within 10 working days of assignment) and maintain an exposure control plan.
- Needlestick first action: wash the site immediately with soap and water, then report and follow the exposure-control plan. The first physical action is washing, not reporting.
- Sharps containers must be rigid, puncture-resistant, leak-proof, and closable; replace before they are full (about three-quarters).
- Hand hygiene is the single most effective infection-control measure. Standard Precautions treat every patient's blood and body fluids as potentially infectious.
- OPIM (other potentially infectious material) includes body fluids but excludes saliva not visibly bloody.
PPE Sequence
| Step | Don (put on) | Doff (remove) |
|---|---|---|
| 1 | Gown | Gloves |
| 2 | Mask / respirator | Eye protection |
| 3 | Eye protection | Gown |
| 4 | Gloves (last, over cuffs) | Mask / respirator |
Doffing is the reverse of donning, and gloves come off first because they are the most contaminated.
Antiseptic by Test, Complications, and Processing
Antiseptic Selection
| Collection | Antiseptic | Reason |
|---|---|---|
| Routine venipuncture | 70% isopropyl alcohol | Standard skin cleansing |
| Blood culture | Chlorhexidine gluconate | Stronger antisepsis to prevent contamination |
| Blood alcohol (BAC) | Benzalkonium chloride / povidone-iodine | Alcohol prep would falsely raise the result |
Always cleanse in concentric circles moving outward and let the site air dry before puncture. BAC is blood alcohol concentration.
Complication Response (memorize the immediate action)
- Sudden shooting pain radiating down the arm: remove the needle immediately — possible nerve involvement.
- Pale, diaphoretic, faint (syncope): stop the draw, lower the head, raise the legs.
- Swelling at the site (hematoma): release the tourniquet, withdraw the needle, apply firm pressure.
- Two failed attempts: stop and ask a colleague to take over.
Processing and Rejection
| Domain must-know | Rule |
|---|---|
| Serum clot time | 30-60 minutes before centrifugation |
| Centrifuge balance | Equal-weight tubes opposite each other |
| Most common rejection | Unlabeled or mislabeled specimen |
| Clotted CBC (lavender) | Absolute rejection — recollect |
| Hemolysis effect | Falsely elevated potassium |
| Labeling timing | At the bedside, before leaving the patient |
Domain to Must-Know Map
| Domain | One thing you cannot miss |
|---|---|
| Routine Collections | CLSI GP41 order of draw + additive carryover |
| Safety and Compliance | OSHA 29 CFR 1910.1030 + PPE don/doff sequence |
| Patient Preparation | Two-identifier patient ID; median cubital is first vein choice |
| Special Collections | Chlorhexidine for cultures; non-alcohol antiseptic for BAC |
| Processing | Unlabeled = top rejection cause; hemolysis raises potassium |
A phlebotomist must draw a light blue (coagulation), lavender (CBC), and gold SST (serum chemistry) tube from one venipuncture. In what order should the tubes be filled?
Which two domains together account for more than half of the 100 scored NHA CPT items?
A patient requires a legal blood alcohol concentration (BAC) draw. Which antiseptic should the phlebotomist use to prep the site?
What is the first action a phlebotomist should take immediately after sustaining an accidental needlestick?
A lavender-top tube submitted for a CBC arrives at the lab with a visible clot. What is the correct laboratory action?