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Pathobio Exam 1
Set 10: Clinical Laboratory
82
Pathology
Graduate
10/17/2011

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Cards

Term
What is the purpose of the lab & clinical pathology?
Definition
1) Confirm/reject Dx
2) Guide patient management
3) Eastablish prognosis/stage
4) Detect occult disease
5) Monitor therapy
6) Estimate disease activity
7) Prevent irreparable damage
Term
What lab protocols must implicitly be followed in order to provide quality lab values?
Definition
1) specimen collection
2) handling
3) processing
Term
What are the 3 settings lab results can be generated from?
Definition
1) Clinical lab
2) POC (point of care)
3) physician's office
Term
When is POC testing appropriate?
Definition
actue condition in which changes are rapid s.a. ER or OR
Term
What is the advantage to POC testing?
Definition
provides "real time" results
Term
Who provides the guidance and training for POC testing?
Definition
clinical lab (they're also responsible to maintain quality control & quality improvement)
Term
What are the tests able to be performed at the physician's office?
Definition
The "waived tests" - easy to perform technically s.a.:
-pregnancy
-rapid flu
-rapid strep
-mono-spot
Term
Why can't physician's offices perform tests beyond the "waived" scope?
Definition
CLIA 88 = amendment issued by Congress to closely regulate lab testing
Term
Who can request tests?
Definition
physician (written or direct order)
Term
What does the physician's order of test generate a list for?
Definition
phelbotomy collection
Term
What must be contained on the order for testing?
Definition
Patient's demographics:
-name
-sex
-age
-DOB
-date of admission
-date of test request
-hospital number
-ordering physician
Term
What 6 things must be considered that the patient can do that may influence lab determinations?
Definition
1) Diurnal variations
2) Physical activity
3) Fasting Status
4) Chronic EtOH
5) Postural changes
6) Drug regimen
Term
def

diurnal variation
Definition
variations that occur every day
Term
What 2 daily serum infiltrates have diurnal variation?
Definition
1) Cortisol
2) Neutrophil count
Term
What is the nature of the diurnal variation of cortisol?
Definition
Highest in morning & lowest around midnigh for ppl w/ normal sleep pattern
Term
What causes the diurnal variation of cortisol?
Definition
ACTH levels
Term
What is the nature of the diurnal variation of neutrophils?
Definition
highest around 4 pm in ambulatory patients, lowest in the morning @ rest.

There is significant individual variation (some who display NO dinural variation)
Term
How does physical activity affect lab values?
Definition
1) Transient increase in some enzymes (CK, AST, LD)
2) Long lasting effect on some lipoproteins
Term
What serum values may change at a 48 hr fast?

72 hours?
Definition
48 hrs:
biliribun increase slightly

72 hrs:
hypoglycemia
increase triglycerides
increase fatty acids
Term
How long should a person fast prior to lab tests to provide an evaluation of the basal rate?
Definition
12 hrs
Term
What happens if a patient chooses not to fast & has a small meal prior to lab tests?
Definition
may affect several parameters including fat, protein, & serotonin
Term
What serum parameters are affected by chronic EtOH use?
Definition
incrase HDL, cholesterol, & some liver enzymes
incease in MCV (mean corpuscular volume)
Term
How can postural changes affect lab values?
Definition
proplonged standing or sitting can cause loss of intravascular fluid due to increased hydrostatic pressure.
Term
What serum levels may be affected by postural changes?
Definition
increased albumin & total protein
increased sm. moleculed bound to serum proteins
increased Hb, Hct & PMNs
Term
What drugs do we expect to see adjusted lab values with?
Definition
1) Cholesterol lowering drugs to affect LDL 2) heparin to prolong aPTT 3) several drugs affect K+ values (up or down) 4) some drugs may have intrinsic properties that affect the assay itself adjusting the numbers
Term
What do the colors of the blood collection tubes mean?
Definition
What is contained in the tube:

Anticoaglulant? Which one?
Term
What color means there's NO additive to the blood collection tube?
Definition
red
Term
Why would an anticoagulant be used?
Definition
to test whole blood or plasma after reparation from the red cells
Term
def

serum
Definition
coagulated blood (plasma with no clotting factors)
Term
def

plasma
Definition
no coagulation (to assess cellular or coagulation factors)
Term
Why wouldn't an anticoagulant be used in blood collection?
Definition
allow the blood to clot & serum to separate
Term
Why must serum or plasma be separated from RBCs?
Definition
prevent an increase in chemicals & enzymes found intracellular
Term
Why is it important to know if blood was collected from a vein or an artery?
Definition
v. & a. differ in oxygen content, pH, CO2, hematocrit
Term
What is the source of most blood collection?
Definition
vein
Term
What are the steps for proper collection of a venous puncture?
Definition
1) patient ID
2) cleanse area
3) application/removal of tourniquet
4) invert tubes containing anticoagulant for mixing
5) proper disposal of sharps
6) check on patient status after draw
7) label tubes
Term
How many times should you attempt a draw before asking for help?
Definition
2
Term
What are the possible complication of venipuncture?
Definition
hematoma
excessive bleeding
thrombosis of vein
infection (rare)
Term
Why is it important to remove the tourniquet at the appropriate time?
Definition
prolonged application can cause hemocencentration => higher Hb & hematocrit
Term
When might a skin punture be used as opposed to a venipuncture?
Definition
pediatric patients (infants)
Term
def

skin puncture
Definition
heel prick is made following 5-10 min exposure to warm water
Term
What values cannot be obtained in a skin puncture?
Definition
blood gas measurements
Term
def

indwelling line
Definition
catheter into vein or artery eliminating need for multiple draws
Term
Function

catheter in vein
Definition
drug & fluid administration
drawing blood
Term
Function

Arterial catheter
Definition
allow continuous, real time monitoring of blood gases & acid base balance
Term
What artery is usually used in arterial catheters?
Definition
radial
Term
Hore catheters kept open?
Definition
heparin, therefore there is need to draw 3-6 mL of blood PRIOR to your actual blood collection if needing cogaulation values
Term
What are the 4 problems associated with blood collection?
Definition
1) short draw
2) hemolysis of blood sample
3) oxylate & citrate can inhibit amylase, lactic dehydrogenase, & acid phosphatase activity
4) sodium & potassium salts in anticoagulant can give false sodium or potassium values
Term
def

short draw
Definition
dilution due to increased ratio of anticoagulant
Term
When drawing multiple tubes, is there an order to the draw?
Definition
Yes, draw the non-additive tubes first (unless blood cluture draw- which should be first)
Term
Why accounts for 1/3 of sample processing time?
Definition
sample transport
Term
Why shouldn't blood samples be agitated during tansportation?
Definition
to avoid hemolysis
Term
Why shouldn't blood samples be exposed to light?
Definition
to avoid breakdown of analytes (i.e bilirubin)
Term
How are unstable constituents of the blood sample transported?
Definition
on ice
Term
What lab processes must be done prior to sample analysis?
Definition
centrifugation, aliquoting & distribution (50% of lab time)
Term
How are patient's IDed in the lab?
Definition
barcode
Term
How are lab results released?
Definition
technician checks the results and the automated system interface releases the analysis to the hospital computer system
Term
def

STAT
Definition
results within 60 min
Term
How quickly are routine testing results available?
Definition
~4 hrs
Term
When can lab results take days to weeks?
Definition
if samples need to be sent out for testing
Term
How is the reference range of a metabolite determined?
Definition
testing a large number of "normal" subjects (not known to have disease) grouped by age & sex

The range is determined by ± 2 standard deviations from the mean
Term
def

critical value
Definition
lab results indicitive of need from prompt clinical intervention
Term
What is the protocol when a critical lab value is noticed by the lab technician?
Definition
1) verify value by repeating test
2) immediately notify ordering physician/nurse
3) document notification
Term
def

sensitivity of a test
Definition
true positive will test positive
Term
Equation

Sensitivity
Definition
true positive/ (true positive + false negative)

(B/c TP + FN = patients with disease)
Term
def

specificity
Definition
true negatives will test negative
Term
Equation

Specificity
Definition
true negative/ (true negative + false positive)

TN + FP = patients w/o disease
Term
When should sensitivity be maximized?
Definition
serious but curable disease
Term
When should specificity be maximized?
Definition
serious, but incurable (since if false negative, it won't change your outcome)
Term
Function

positive predictive value
Definition
determines the likelihood that someone with a positive test has the disease
Term
Equation

postivie predictive value
Definition
= true positive/ (true positive + false positive)

TP + FP = total positives
Term
What is the purpose of tests?
Definition
to reduce clinical uncertainty
Term
What type of test is needed to rule out a disorder?
Definition
very sensitive therefore negative = negative
Term
What type of test should be used to confirm a Dx?
Definition
specific therefore positive = positive
Term
Does a single test lead to a Dx?
Definition
No, at least 1 more test should be done to confirm any Dx
Term
When is an abnormal result more likely to indicate an actual abnormal result?
Definition
the further it is from the normal range
Term
When can a result in the normal range be considered abnormal?
Definition
when different from the patient's baseline
Term
When should lab tests be ordered?
Definition
only if likely to help in:
Dx
management
prognosis
Term
How often should tests be done to follow progress of a disorder?
Definition
depends on the dynamics of the analyte you're testing and the treatment
Term
What is the most common source of errors in results?
Definition
pre-analytical errors:
incorrect draw
incorrect patient
mislabeling of specimen
Term
What happens if the lab instruments give an erroneous result?
Definition
1) try to correct
2) obvious there was an issue with the smear
Term
def

delta check
Definition
automatic comparison of a sample to the patient's previous samples to avoid random analytical errors

if delta check fails, test automatically re-ran
Term
What is the concern when multiple lab tests are repeatedly requested?
Definition
iatrogenic anemia
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