VTNE Review: Laboratory Testing

hematology

the study of the blood elements

whole blood

• consists of blood cells, suspected in a fluid component (plasma)

• blood cell constituents are leukocytes (WBC), erythrocytes (RBC), and thrombocytes (platelets)

plasma

the fluid part of the whole blood

90% water and 10% proteins, carbs, vitamins, hormones, fats, salts, enzymes, and wastes

serum

plasma that has had fibrinogen removed

purple/lavender top tube

• contains EDTA as the anticoagulant

• prevents coagulation by binding calcium ions

• cell constituents are stable for up to 24 hours

• used for running CBC, hematocrit/packed cell volume, reticulocyte count

• also used for collecting fluid that may clot from body cavities in which cell counts needs to be performed (cerebrospinal fluid, peritoneal or pleural effusions, and synovial fluid)

• samples are not centrifuged because there is no clot to be separated

plain red top tube

• glass tube has no additives; plastic tubes have clot activators

• used in immunology and in some serologic tests

• can also be used as a sterile tube for collecting samples for culture such as urine

tiger top tube

• serum separator; contains a clot activator and gel for serum separation

• used for chemistry panels and are used to check any laboratory value seen on these panels and other tests requiring a serum sample

• used for the majority of blood tests

light blue top tube

• contains sodium citrate, an anticoagulant that binds calcium in the blood

• for accuracy, these tubes must be completely filled to recommended level (9 parts blood to 1 part citrate)

• used to check for coagulation disorders (PT, PTT, Fibrin Degradation Products, D-dimer, von Willebrand factor)

green top tube

• plasma separator tube, contains heparin

• heparin activates antithrombins, which block coagulation

• produces a whole blood/plasma sample and is used for collecting a plasma sample

gray top tube

• contain sodium fluoride which is best known as a glucose preservative and some contain potassium oxalate

• used if an accurate glucose measurement is needed and sample processing will be delayed