6.2 Order-of-Draw & Scenario Drills
Key Takeaways
- Rapid recall is the goal: you should produce the full CLSI GP41 order of draw and each tube's additive in under ten seconds without reasoning it out
- Tube-to-test matching is a guaranteed item type — lavender/EDTA equals CBC, light blue/citrate equals PT/INR/aPTT, gray/fluoride equals glucose, gold SST equals serum chemistry
- Complication scenarios test the immediate action, not the diagnosis — remove the needle for nerve pain, lower the head for syncope, apply pressure for a hematoma
- Special-collection antiseptic items hinge on one rule: alcohol for routine, chlorhexidine for cultures, non-alcohol for blood alcohol levels
- Capillary collection reverses the order of draw — EDTA/lavender is filled before serum tubes to avoid platelet clumping and clotting
How to Use These Drills
Quick Answer: Pattern recognition wins this exam. The order of draw, tube-to-test pairings, and immediate complication actions appear as the same question structures every time. Drill them until the answer is automatic, then the exam becomes a recall exercise instead of a reasoning exercise.
Work each quiz below cold — do not look back at Section 6.1 first. If you miss one, write the underlying rule on a single index card and re-drill it the next day. The goal is speed plus accuracy: on a 120-item, 2-hour exam you have roughly one minute per item, and recall items should take you ten seconds so you can spend time on the reasoning items.
The Self-Test Sequence
- Recite the order of draw out loud: culture, light blue, red/SST, green, lavender, gray.
- For each tube, say the additive and one test.
- State the inversion count for lavender, light blue, green, and red.
- For three complications, state the first action in five words or less.
If any step stalls, that is your weak spot for the final week.
Tube-to-Test Quick Map
Use this table only to check yourself after the drills, not before them.
| Test ordered | Correct tube | Additive |
|---|---|---|
| CBC, ESR | Lavender | EDTA |
| PT, INR, aPTT | Light blue | 3.2% sodium citrate |
| STAT electrolytes / plasma chemistry | Light green PST or green | Lithium/sodium heparin |
| Serum chemistry, serology | Gold SST or red | Clot activator + gel / none |
| Glucose, lactate, blood alcohol | Gray | Sodium fluoride / potassium oxalate |
| Blood culture | SPS bottles | Sodium polyanethol sulfonate |
| Type and crossmatch (blood bank) | Pink | EDTA |
Inversion Reminders
- Red plain: 0 inversions (no additive to mix).
- Light blue: 3-4 gentle inversions.
- Gold SST: 5 inversions.
- Green, lavender, gray: 8-10 inversions.
- Mixing is always gentle — never shake, which causes hemolysis.
A single venipuncture must fill these tubes: blood culture set, gray, light blue, and lavender. What is the correct fill order?
A provider orders a PT/INR and a CBC on the same patient. Which tubes are required?
Midway through a venipuncture the patient reports sudden, severe shooting pain radiating down the forearm. What should the phlebotomist do first?
A phlebotomist must collect a capillary specimen requiring both an EDTA microtube and a serum microtube. In what order should they be filled?
A blood culture and a routine chemistry draw are ordered. Which antiseptic is correct for each site preparation?