Blood sample for microbiological tests is collected in specialized bottles; all these bottles are of a particular design, but the color of their cap reveals many secrets about that vial. This color code of the vial plays a vital role in understanding the vial, i.e., what the vial contains, and which test is to be performed on the blood sample. Blood shows various changes when taken out of the body. Blood samples require some particular additives to prevent unnecessary changes in blood composition or constituents, and maintain the blood's specific composition according to the test's requirements. To save time and effort before performing any test, the additives are added to the vial at the time of its manufacturing. To avoid confusion about the additive present in the vial, the color of the tubes is standardized globally, so each color corresponds to a specific lab test because of its specific additive. This color code is a voice of a vial about instant recognition of its purpose along with accurate collection & processing of the blood sample. Cracking this color code is a step forward to empower knowledge before entering a laboratory or sample collection room.
|
Cap Color |
Additive |
Sample Type |
Mechanism |
Used For Test |
What it Reveals |
Visual |
|
Red |
None |
Serum |
Serum is separated after centrifugation of naturally clotted blood |
Liver/Kidney function, serological, hormone, blood grouping |
Organ Function, Cholesterol, Infection Marker |
|
|
Blue |
Sodium Citrate |
Plasma |
Binds calcium to prevent clotting; calcium is re-added in the lab |
Coagulation studies (PT, aPTT, INR) |
Clotting ability, bleeding risk |
|
|
Lavender/ Purple |
EDTA |
Whole Blood or Plasma |
Binds calcium to prevent clotting and preserve cells' shape |
CBC, ESR, HbA1c, blood typing |
Blood counts, Blood cancer, anemia, and immune health |
|
|
Green |
Heparin |
Plasma |
Prevents clotting by inhibiting thrombin and other clotting factors |
Electrolytes, ammonia, blood gases, cardiac markers |
Electrolyte imbalance, acidosis, liver/kidney disorders |
|
|
Yellow |
Acid Citrate Dextrose or Sodium Polyanethol Sulfonate |
Whole Blood |
ACD- Binds Calcium to prevent clotting SPS- Preserves cells or inhibits bacterial growth |
Blood cultures, genetic testing, tissue typing |
Genetic marker, blood infections, and organ transplant compatibility |
|
|
Black |
Buffered Sodium Citrate |
Whole Blood |
Allows RBCs to settle over time |
ESR |
Inflammatory conditions, chronic disease markers |
|
|
Pink |
EDTA |
Whole Blood |
Preserves red cells for compatibility testing |
Crossmatching, blood grouping |
Blood type match for transfusion |
|
|
Grey |
Sodium Fluoride and Potassium Oxalate |
Plasma |
Inhibits glycolysis |
Glucose, Lactate testing |
Diabetes, metabolic acidosis |
|
|
Gold |
Clot activator & Separation gel |
Serum |
Clot activator forms Clot, and gel forms a barrier after centrifugation |
Vitamin level, liver/kidney functioning, infectious diseases like HIV, Hepatitis |
Organ function, cholesterol, and metabolic screening |
|
|
White |
EDTA & Separation gel |
Plasma |
EDTA prevents clotting, and gel forms a barrier after centrifugation |
PCR, HIV, HCV, DNA assay |
Viral RNA/DNA levels, genetic material for diagnostic testing |
|
