Laboratory Medicine Flashcards
serum uses
- most tests that measure antibodies
2. serum protein electrophoresis
whole blood uses
- heavy metals
- hematology
- transplant immunosuppressants
how to obtain plasma
centrifuge tube of blood, supernatant is plasma, tubes contain anticoagulants to prevent clotting
how to obtain serum
allow blood to clot, everything NOT clotted is serum
Use of red top tube (no additive-refers to no anticoagulant)
plastic tube w/ clot activators, sample usually clots w/in 30 min aided by tube inversion, uses-serology, protein electrophoresis, mailout tests
drawbacks of red top tube
time for clot to form, microclots can interfere w/ automated instruments
use of serum separator tube
common for doctor’s offices that refer most tests to commercial labs - Gel prevents clotted cells from contaminating serum
EDTA (lavender/pink tops) tube uses
EDTA chelates Ca & prevents blood clotting, uses - tests that require whole blood or plasma - hematology, molecular diagnostics, drug tests requiring whole blood
plasma separator tube (PST) uses
anticoagulant is lithium heparin, gel goes b/w plasma & cells after centrifugation - tube of choice for UIHC for most chemistry assays
plasma separator tube drawbacks
cannot use for lithium drug levels due to lithium heparin used as anticoagulant
light blue top tube (sodium citrate)
tube of choice for coagulation tests - problem is inadequate filling of tubes leading to too much anticoagulant relative to blood
royal blue top tubes
required for certain trace metals analysis - DO NOT NEED FOR BLOOD LEAD ANALYSIS EDTA TUBE IS FINE
proper draw order for tubes
- blood cultures - yellow top
- citrate tube - light blue
- Serum tube - red top
- Heparin tube/PST - light green top
- EDTA tube - purple top
- Fluoride tube - gray top
common interferences & testing issues
hemolysis, lipemia, icterus
causes of hemolysis
can be due to disease or MORE OFTEN related to blood draw technique (narrow gauge needle, too rapid, contamination)
problems caused by hemolysis
- false elevation b/c RBCs contain analyte being measured - AST,LDH,K+
- RBC lysis reduces what is being measured (proteases are released that degrade peptides) - insulin
hemolytic index
300 = sever
Cause & problems of lipemia
due to elevated lipids & mostly effected by high triglycerides, extreme lipemia (triglycerides > 1,000 md/dL) can interfere and also cause hemolysis
cause of icterus
high bilirubin can lead to yellow or yellow-brown plasma, can lead to test cancellation if bilirubin is > 40mg/dL
method of inpatient reimbursement
bundled payment arrangement such as diagnosis-related groups
i.e. fixed payment for inpatient stay
outpatient reimbursement method
increasing trend for outpatient encounters toward bundled payments - applies to common lab tests INCLUDING Pap smears
charges vs. cost of tests
charges are set by hospital financial - insurance only pays fraction & self pay patients can be responsible for full charge
-actual costs of tests usually lower than charges
patient liability for tests
COMPLICATED
- outpatient: major issue is pre authorization for expensive tests
- inpatient: have to consider deductibles, co-insurance, & max caps
Clinical Laboratory Improvement Act (CLIA)
- passed in 1988, revised in 2003
- established federal gov. oversight of clinical labs including small labs in doctor’s offices
- enforced by center for medicare and medicaid services (CMS)
