Laboratory Medicine Flashcards
Plasma
supernatant after centrifugation of blood. Contains anitcoagulants to prevent clotting. used for chemistry tests
Serum
allow blood to clot, supernatant is serum. Used for tests measuring antibodies.
Whole blood
blood counts, heavy metals, transplant immunosuppressants
Red top tubes
contains clot activators. takes 30 minutes. microclots can cause interference
Serum separator tube
special gel that migrates between clot and serum to prevent clot contamination
EDTA tubes (lavender or pink tops)
chelates Ca2+ and prevents clotting. CANNOT be used for Ca and Mg tests. Used for whole blood or plasma.
Plasma separator tube
lithium heparin- after centrifugation, gel goes between plasma and cells. can’t be used for lithium drug levels
Sodium Citrate (light blue top)
Tube of choice for coagulation tests (PT, PTT, coagulation factors). Must be filled accurately.
Trace metal-free (royal blue)
certain trace metals-arsenic, cadmium, mercury, zinc. not needed for lead
What tube would you use for serology?
red top tube
What tube would you use for lead levels?
EDTA tubes (lavender or pink top)
What tube would you use for serum?
serum separator tube
What tube would you use for whole blood or plasma, and is used for hematology and molecular diagnostics?
EDTA (lavender or pink top)
which tube cannot be used for lithium drug levels?
Plasma separator tube (lithium heparin)
What tube would you use to analyze cadmium, mercury, arsenic, or zinc?
trace metal-free (royal blue)
What tube would you use for coagulation tests Pt PTT?
Sodium citrate (light blue top)
what tube has the common problem of not being filled fully resulting in elevated levels?
sodium citrate (light blue top)
What order must blood draws be performed?
blood cultures (sterility) goes first. Tubes that can cross contaminate go at the end (EDTA).
Poor blood draw technique or poor gauge needle choice can cause what testing issue
hemolysis. can also be caused by diseases such as malaria.
Interference of testing due to hemolysis caused by what two mechanisms.
false elevation because RBC contain high amounts of AST, LDH (lactate DH), and K.
RBC lysis reduces what’s being measured, proteases degrade peptide like insulin.
Lipemia in testing
turbid specimens usually due to high triglycerides. Extreme lipidemia >1000mg/dL can cause lipemia and hemolysis
Icterus in testing
high bilirubin can lead to yellow plasma. very high bilirubin >40 mg/dL can interfere with chemistry tests.
requirements on complexity of testing set by the CLIA
waived, moderate complexity, high complexity. Must have certificate to cover highest complexity in lab.
