Step 1
Yellow / Sterile
SPS (Sodium Polyanethol Sulfonate)
Blood CulturesMicrobiology
Always drawn first to protect sterility — any additive carryover can invalidate cultures.
Order of Draw
The CLSI GP41 venipuncture sequence. Drawing in this order prevents additive carryover between tubes and protects result integrity — work top to bottom.
| Step | Tube / Cap | Additive | Inversions | Common Tests | Critical Rule |
|---|---|---|---|---|---|
| 1 | Yellow / Sterile | SPS (Sodium Polyanethol Sulfonate) | 8–10 | Blood CulturesMicrobiology | Always drawn first to protect sterility — any additive carryover can invalidate cultures. |
| 2 | Light Blue | Buffered Sodium Citrate (3.2%) | 3–4 | PT / INRaPTTD-DimerFibrinogen | Must fill completely to the fill line — the 9:1 blood-to-citrate ratio is mandatory. |
| 3 | Red / Gold / Tiger Top | Clot Activator / SST Gel (or none, plain red) | 5 | CMPTroponinLipid PanelThyroid StudiesSerology | Allow a full 30 minutes to clot before centrifugation. |
| 4 | Green | Sodium / Lithium Heparin | 8–10 | STAT ChemistryPlasma PanelsAmmoniaElectrolytes | Invert immediately; never use for hematology — heparin distorts cell morphology. |
| 5 | Lavender / Purple | EDTA (K2 / K3) | 8–10 | CBCType & ScreenHbA1cESRReticulocyte Count | Immediate, complete inversion prevents micro-clots that invalidate the CBC. |
| 6 | Grey | Sodium Fluoride / Potassium Oxalate | 8–10 | GlucoseLactateEthanol Level | Fluoride inhibits glycolysis — preserves glucose for up to 24 hours. |
- 8–10
- 3–4
Step 2
Light Blue
Buffered Sodium Citrate (3.2%)
PT / INRaPTTD-DimerFibrinogenMust fill completely to the fill line — the 9:1 blood-to-citrate ratio is mandatory.
- 5
Step 3
Red / Gold / Tiger Top
Clot Activator / SST Gel (or none, plain red)
CMPTroponinLipid PanelThyroid StudiesSerologyAllow a full 30 minutes to clot before centrifugation.
- 8–10
Step 4
Green
Sodium / Lithium Heparin
STAT ChemistryPlasma PanelsAmmoniaElectrolytesInvert immediately; never use for hematology — heparin distorts cell morphology.
- 8–10
Step 5
Lavender / Purple
EDTA (K2 / K3)
CBCType & ScreenHbA1cESRReticulocyte CountImmediate, complete inversion prevents micro-clots that invalidate the CBC.
- 8–10
Step 6
Grey
Sodium Fluoride / Potassium Oxalate
GlucoseLactateEthanol LevelFluoride inhibits glycolysis — preserves glucose for up to 24 hours.
SequenceYellowLight BlueRedGreenLavenderGrey